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The cost of AIDS: An agenda for research
Health Policy, Elsevier
11 (1989) 197-208
197
HPE 00264
The cost of AIDS: an agenda for research* Anne A. Scitovsky Health Economics Division, Palo Alto Medical Foundation/Research Institute, Palo Alto, CA, U.S.A. Accepted
31 December
1988
Summary It is generally not appreciated how much we have learned about AIDS in the relatively short time - about 7 or 8 years - since it made its first appearance in the United States. We have learned not only its cause and its way of transmission, but we also have data, though not perfect data, on its incidence and prevalence as well as an increasing body of data on the medical care costs of persons with AIDS. There are few other diseases for which we have as much information on incidence and prevalence, and especially on costs. In addition, various models have been constructed to project the future incidence and prevalence of the disease and the medical care costs associated with it. Nevertheless, serious gaps in our knowledge remain: inadequacies of current data on the number of persons with AIDS and especially on the number of persons infected with HIV; inadequacies and limitations of the data on the medical care costs of persons with AIDS; and an almost total lack of data on the number of persons infected with HIV with symptoms and conditions other than AIDS and their medical care costs. These gaps in our knowledge will be discussed in detail, and various types of studies to fill them will be suggested. AIDS; HIV; Research agenda;
U.S.
*This article is based on a paper presented at the conference, search Methodology’, held at The Johns Hopkins University Baltimore, MD on September 27-28, 1988.
‘The Economic Impact of AIDS: ReSchool of Hygiene and Public Health,
Address for correspondence: A.A. Scitovsky, Chief, Health Economics Division, Foundation/Research Institute, 860 Bryant Street, Palo Alto, CA 94301, U.S.A.
0168-8510/89/$03.50
0
1989 Elsevier
Science
Publishers
B.V. (Biomedical
Division)
Palo Alto Medical
198
1. Introduction In this paper I discuss the many data gaps that still exist with respect to AIDS, and my ideas for an AIDS research agenda. Before doing so, I want to strike a more positive note. It is important to recognise how much work has been done and how much we have learned about the HIV epidemic in the barely 8 years since the disease first made its appearance in the United States. In some respects, we already know as much or more about AIDS than about many other diseases that have been around far longer. To begin with data on incidence and prevalence, we have data on incidence for some major diseases, mainly the various forms of cancer, collected by the American Cancer Society; but we have no data on the prevalence of these conditions. Thus we do not know, for example, how many women with breast cancer are alive at any given time or in the course of a year. Conversely, for the major chronic conditions we have data on prevalence from the Health Interview Survey of the National Center for Health Statistics (NCHS), but we have no data on the incidence of these conditions. Moreover, the data are limited to the civilian, non-institutionalized population and thus omit some important sectors of the population, such as nursing home patients and the military. When it comes to the national costs of other diseases, our knowledge is also rather limited. We have prevalence-based estimates for the 16 broad categories of the International Classification of Diseases (ICD) ( i.e. infective and parasitic diseases, neoplasms, diseases of the circulatory system, etc.) by Dorothy Rice and her colleagues at NCHS [l]. These same researchers have also made prevalencebased estimates of specific cancers by site (16 in all) [2]. Apart from these studies, there are about half a dozen other prevalence-based estimates of various broad groups of conditions - respiratory conditions, musculoskeletal conditions, dementia. Incidence-based estimates of the costs of specific conditions are even rarer. The major work in this area was done in the 1970s by Hartunian et al. on cancer, coronary heart disease, stroke and motor vehicle accidents [3]. More recently (1983), Hay and Ernst did an incidence-based cost estimate of Alzheimer’s disease [4]. Let me add that some of these incidence-based studies estimate aggregate costs only, not lifetime costs per patient. To sum up, our data on the incidence and prevalence of AIDS and of its direct medical care costs compare not unfavorably with corresponding data for other major illnesses, despite the fact that AIDS has a relatively short history compared to these other conditions. AIDS has also received more attention than could be expected on the basis of the number of cases compared to the number of cases of other major illnesses. The incidence of AIDS in 1987 was 22948 and I estimated its prevalence in that year at about twice its incidence, or about 45 900. The CDC estimates its incidence in 1991 at about 70000 cases, which would make its prevalence in that year about 140000, again assuming prevalence to be twice the incidence. The incidence data for various forms of cancer for 1987 (from the American Cancer Society) are as follows [5]:
199
Lung cancer Cancer of the Cancer of the Cancer of the Cancer of the Cancer of the
colon breast prostate urinary system uterus
150 000 145 000 130 900 96 000 67 300 47 800
In other words, the incidence of all but the last two was very much higher in 1987 than the projected incidence of AIDS in 1991, not to mention its incidence in 1987. However, Harris’ estimate of AIDS incidence of 70000 a quarter by 1996 puts the incidence of AIDS higher than the current incidence of any of these diseases, though of course their incidence is also likely to be higher in 1996 than currently [6]. Prevalence data show even greater differences between AIDS and some other conditions. The NCHS Health Interview Survey shows the following prevalence data for 1986 [7]: 9.9 million cases Asthma 6.9 million cases Ischemic heart disease 4.5 million cases Ulcer of the stomach and duodenum 2.0 million cases Emphysema 1.7 million cases Rheumatic fever Thus the prevalence of these conditions currently exceeds Harris’ high estimate of 642000 AIDS cases in 1996. I cite these data on other diseases not to suggest that we have done enough research on the various aspects of the HIV epidemic but to give the AIDS data a frame of reference, some perspective, and to remind us how much has already been accomplished despite the many gaps in our knowledge which require further research. Clearly there are special features of the epidemic which call for special efforts. - AIDS is invariably deadly, with no cure or vaccine currently available nor likely to be available in the near future. - It affects mainly young people, with 67% of all cases in the 20- to 39-year age group and 88% in the 20- to 49-year age group [8]. - It is expensive to treat, though in the absence of lifetime cost data on other major illnesses, it is difficult to estimate where on the cost-per-illness curve it lies. - It has been concentrated in a number of metropolitan areas, with the 10 SMSAs with the largest number of cases accounting for 56% of all cases reported to date (September 5, 1988) and the 20 SMSAs with the largest numbers accounting for 68% of all cases. Even though it is now spreading beyond these centers, they will continue to face the most severe demands on their health care systems [9]. - Last but not least, there is the fear of the disease - it is new, it is infectious, it is deadly, and there is the fear of where it will spread. This element of fear makes it comparable to polio before the advent of a vaccine. It too was a disease which in terms of incidence did not rank high compared to many other diseases but was given a high research priority.
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2. Agenda for research: major gaps in our knowledge After this somewhat lengthy introduction, let me turn to my topic, the major gaps in our knowledge of AIDS which call for further research. My comments fall into 3 broad groups: (1) comments on the models for projecting the incidence of AIDS, and for estimating the costs of AIDS; (2) major data gaps and further research needs for estimating the prevalence of HIV infection and the incidence and prevalence of AIDS; and (3) major data gaps and further research needs for estimating the costs of AIDS and HIV infection in general; most of my comments will focus on this last topic.
Models I have little to say about the models for projecting the number of persons infected with HIV and of AIDS cases. In view of the many uncertainties, it is clear that a variety of models should be used and their results compared. Because the populations at risk are different in different geographic locations, local projections - by state or region - may be better than national projections. I shall also be brief about the models for estimating the medical care costs of persons with AIDS. The Bilheimer model is the more traditional and estimates costs as a function of the major parameters known to affect costs, e.g. geographic location, annual AIDS incidence, risk group distribution, presenting diagnosis, etc. [lo]. The model proposed by Hay uses a medical decision algorithm approach [ll]. Bilheimer recommends her model for estimates on the state level rather than the national level, and I would suggest that Hay’s model should also be used on a subnational level, possibly for a region or even an SMSA. We know that hospital treatment of persons with AIDS differs markedly by geographic area, with hospital length of stay considerably lower in San Francisco than in New York or Boston, and in the West in general compared to other areas of the country. We also know from the work of Wennberg that there are large differences in treatment patterns of specific medical conditions even within relatively small areas. As in the case of the models for projections of the number of AIDS cases, I suggest that both the Bilheimer and Hay models be experimented with, possibly for a state or an SMSA and the resulting cost estimates compared. To sum up, I think we have satisfactory models for estimating the incidence and costs of AIDS. This does not mean that they should not be modified as additional data become available. But they are flexible enough to be adapted to changing circumstances. Our major research needs as I see them, therefore, are not additional models but rather more data to put into the models.
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Research needs: estimates AIDS
of HIV infection
and incidence
of
With regard to estimating the prevalence of HIV infection and the number of AIDS cases in future years, I see several areas that need further study. As Dondero has described, the CDC are planning a two-phased study involving anonymous and confidential blood testing for seroprevalence [12]. The first phase was to be a one-year pilot test in several metropolitan areas beginning last summer (1988) to assess in part whether the response rate is high enough to obtain meaningful results in a broader study. If results look promising, the second phase would survey approximately 50000 households, with results becoming available in 1990. I understand that the first phase of the pilot study, conducted in Washington, DC, last summer, ran into serious problems and that the CDC are now considering attempting the study in some other areas. I see two additional problems with respect to estimating the number of AIDS cases which need further study. One is the problem of under-reporting. The Centers for Disease Control (CDC) have estimated that under-reporting of AIDS cases may be as high as 20%. However, I suspect that this under-reporting is not uniform across risk groups and areas, and especially that AIDS cases who are iv. drugusers may be under-reported to a greater extent than homosexual males. If this is the case, under-reporting is a special problem in the areas where i.v. drug-users are concentrated, by and large the Northeast, and in particular the New York-Newark and Jersey City-New Jersey areas. If these centers, whose medical resources are already under severe strain, are to make plans for providing services for future AIDS cases, it is essential to assess the extent of under-reporting in their service areas. We also need data on the number of cases with the conditions added to the CDC definition of AIDS last year, the so-called ‘wasting syndrome’ and dementia. To date, the CDC have not listed figures for these two new conditions separately in their AZDS Weekly Surveillance Reports but apparently include them with ‘other opportunistic diseases’. In addition to better data on the incidence of AIDS, we also need data on other HIV-related conditions short of full-blown AIDS, conditions which in the past have been referred to as AIDS-related complex (ARC). There are no data on the number of ARC cases, but they have been variously estimated at 2 to 5 or 6 times (and up to 10 times) the number of AIDS cases. Nor are there any data on their life expectancy or number of months or years from diagnosis to death or conversion to AIDS. To obtain data on these cases, a definition of the conditions covered by this group of less-than-full-blown AIDS is needed, as well as cohort studies to determine the length of time patients live with these conditions before converting to AIDS or dying.
202
Research needs: estimates of the direct personal health care costs of persons with AIDS Nationwide
cohort studies of AIDS
This brings me to data gaps and research needs with regard to estimating the medical care costs of persons with AIDS. The empirical studies conducted to date, with one exception (Andrulis’ study of AIDS patients treated in public and private teaching hospitals [13], have been limited to a few geographic areas - San Francisco, New York and Massachusetts. In addition, most are limited to inpatient hospital services or at best to inpatient and outpatient hospital services. All of them have been retrospective, so that their data are likely to be somewhat outdated by the time they were completed, considering how fast treatment of AIDS is changing. Finally, the studies used different methodologies of data collection and analysis. For all these reasons, they do not provide a good basis for even rough estimates of the national costs of AIDS. Under a contract with the National Center for Health Services Research (NCHSR), my research team (consisting, in addition to my co-workers at the Palo Alto Medical Foundation, of experts from SRI International, University of California San Francisco and New York University) has developed a research protocol for conducting a nationwide study of the costs of the medical, social and support services of persons with AIDS. The study would consist of prospective studies conducted at 8 geographic sites, in which cohorts of persons with AIDS would be followed for one year and all data on their use and costs of services collected from or on behalf of them. While the study will still not provide the basis for a statistically unbiased estimate of the national costs of AIDS, it will provide much better data for at least approximate estimates because it is a prospective study, covers representative geographic areas (and within each site, representative providers of care), obtains more complete data than previous studies, and last but not least uses a uniform methodology of data collection and analysis. This kind of study is expensive. It would be interesting, therefore, if parallel studies were conducted in 2 or 3 of the NCHSR sites using Hay’s medical decision algorithm approach and the results of the two approaches compared. If the results were similar, one could possibly use his method in the future at least in part as a substitute for the cohort studies. I say ‘in part’ because I doubt that the algorithm approach can capture all the social and support services persons with AIDS rely on. I also want to repeat that they should be used for local (State or metropolitan) rather than national estimates. In addition to the need (as I see it) for a comprehensive nationwide study of the costs of AIDS, there are areas for further research, which the nationwide study will either not cover at all or cover only partially. Data on costs of special groups
There is, first of all, the problem of the costs of care of special groups of persons with AIDS. The studies conducted to date have been predominantly of homosex-
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ual males. It is generally assumed that persons with AIDS who are i.v. drug-users have higher medical care costs than homosexual males, primarily because they are more likely to present with Pneumocystis carinii pneumonia (PCP), which is more expensive to treat than Kaposi’s sarcoma (KS), a presenting diagnosis more common among homosexual males. However, there are no conclusive data on possible cost differences between the two groups. An unpublished report by the New York State Department of Health some years ago found no difference in the average length of hospital stay and average charge per hospital day between persons with AIDS who were i.v. drug-users compared to all others with AIDS. Moreover, the CDC data indicate that the relative importance of KS as a presenting diagnosis has been declining. In 1987, through September 7, 10% of all newly reported cases had a presenting diagnosis of KS. During the same period in 1988, the percentage had dropped to 6%. Even in absolute terms, the number of newly reported KS cases in 1988 (through September 5) was only 9% more than during the same period in 1987, while the number of cases reported with PCP rose by 45% and that of other opportunistic diseases almost tripled. This change in the distribution of cases by presenting diagnosis may be due to the increase in the percentage of new i.v. drug-user cases from 15% in 1987 (through September 7) to 24% in 1988 during the same period. But the data are not conclusive. Thus data on the use and costs of services of this group are presently lacking and need special study. The proposed national study will provide some data for this group, but possibly some additional local studies with larger samples of i.v. drug-user AIDS cases are necessary . Women and children with AIDS are another group for whom no cost data are available. The percentage of new cases of women with AIDS has risen from 7% in 1987 (through September 7) to 10% in 1988 (through September 5), that of new pediatric cases from 1.3% in 1987 to 1.8% in 1988. [14]. It is possible that the costs of female AIDS patients are similar to those of males, but pediatric cases very likely have different treatment and cost patterns. They are likely to have longer hospital stays because it seems many of their mothers have either died of AIDS or abandoned them. In addition, they are difficult to place in foster homes. Because about one-third of the pediatric cases are in New York City, this would be a good site for a pilot study. Data on payers of care
Second, there is the lack of data on payers of care and amounts paid by different payers. While some of the studies conducted to date indicate ‘expected source of payment’ or even average cost per patient by type of insurance coverage (e.g. Seage’s 1984 Massachusetts study) [15], there are no good data for estimating the distribution of total national costs by source of payment. An AIDS patient’s insurance status is likely to change over his or her lifetime: he/she may start with private insurance, go to self-pay when he/she can no longer work and loses insurance coverage, and finally qualify for Medicaid if he/she has spent down to Medicaid eligibility levels or, if he/she lives long enough, may qualify for Medicare un-
204
der the Social Security Disability Insurance program which requires a two-year waiting period. This latter possibility is becoming more likely as life expectancy of persons with AIDS increases. Thus the best way to obtain good data on the distribution of costs by source of payment is probably by cohort studies of representative groups of AIDS patients. I know from my own past cost-of-illness studies that this is time consuming and costly. Patients often do not know who paid how much for what, and Medicaid patients do not know at all how much was paid on their behalf. Thus it would be helpful to get data also from third-party payers. To date, however, neither Medicaid data nor data from insurance companies and the Blues have been very useful, although they are all now making efforts to improve their AIDS data. Efforts should therefore be made to collect and evaluate these data as they become available and to use them as the basis for estimating the distribution of the costs of care by principal payers. Data on services provided
by volunteers
and families of persons with AIDS
A third important area for further research is a comprehensive survey of the amount and kinds of social and support services provided to persons with AIDS by volunteers and the patient’s lovers and families. Arno has done some very valuable work on this subject, but it needs wider study [16]. It is well known that costs of AIDS in San Francisco have been held down by the network of community support systems which were organized largely by the gay community and staffed to quite an extent by volunteers. This has enabled AIDS patients to be discharged sooner from the hospital or in some cases be taken care of at home and avoid hospitalization altogether. Other metropolitan centers have made efforts to adapt this so-called ‘San Francisco model’, I do not know with what success. I believe this subject should have a high priority for research. We have to know the types and amounts of services currently being provided by volunteers not only because such data are of general interest currently but also for making plans for the future. I doubt very much that in centers like New York, where a high percentage of persons with AIDS are i.v. drug-users, the San Francisco model can be duplicated. Moreover, it may not function indefinitely even in San Francisco. Not only is the supply of volunteers unlikely to keep up with the increase in the number of cases expected in the next few years, but even some of the current volunteers may ‘burn out’ or come down with AIDS themselves. The same is true for lovers and family members of persons with AIDS. If paid personnel will eventually have to be substituted at least in part for volunteers and family members, the sooner we have data on the basis of which to estimate the number and type of paid personnel who will eventually have to take over the better. Data on costs of new medical treatments
and methods
of delivering
care
To date there are no data on the costs associated with new medical treatments, notably the use of AZT. We have done a very small pilot study at San Francisco General Hospital which suggests that in the first 12 months of treatment with AZT,
205
AZT patients have significantly lower hospital costs and also lower total costs than a matched group of AIDS patients on conventional treatment. Let me stress that it is a small study. But even if the findings are proved correct by other studies (however, I do not know of any other studies), this is not conclusive because the data are for the first 12 months only and did not cover AZT patients to death because none of the patients on AZT died in the first 12 months while the patients not on AZT all died. Thus we do not yet have data on the lifetime costs of patients on AZT, whose terminal care costs may be as high as those of other persons with AIDS. I suggest that in future Phase 2 drug trials, a use and cost data collection protocol be incorporated from the beginning. Similarly, there are no data yet on the possible cost savings of new models of delivering care to persons with AIDS, such as case management. I trust that the Robert Wood Johnson Foundation and Health Resources and Services Administration (HRSA) demonstration projects will be carefully evaluated to shed light on this subject, and I hope that additional studies in this area will be undertaken. Data on HIV-related
conditions
other than AIDS
So far, I have limited my discussion to research needs on the costs of AIDS. But we also need some studies of the costs of the conditions which used to be classified as ARC. To date, we have some data from the 1987 California Health Department’s Medical study which estimates the monthly Medical costs of a person with ARC at about $652, or about 27% of the monthly costs of a person with AIDS. But in the absence of data on the length of time a patient lives with ARC (before either dying or converting to AIDS), no estimates of lifetime costs are available. Data on medical care use and costs of asymptomatic
HIV-infected
persons
Finally, I suggest that we begin some research as soon as possible on the medical care use and costs of asymptomatic (or mildly symptomatic) HIV-infected persons. Their current use of health services is probably relatively small, though there is some evidence that the ‘worried well’ in the general population account for quite a large share of health care expenditures; and there is every reason for members of the groups at risk of HIV infection to be among the ‘worried well’. But my reasons for this suggestion are not so much getting information on their current use of medical services as to provide a basis for estimating their future use. If current small-scale experiments with treating asymptomatic HIV-infected persons with drugs such as AZT to delay or possibly even prevent progression to AIDS prove promising, I expect a large increase in the demand for such treatment, for which we are not prepared at this stage, either in terms of the necessary resources especially in the metropolitan centers where AIDS is already causing a major strain on their health care system, or in terms of financing such care. The financing problem is especially intricate. Such persons are presumably not sick and, if they have jobs, can continue to work and in most cases continue to be covered by their health insurance plans. But drug costs (if they are like ‘those of
206
AZT) are high - AZT costs between $8000 and $10000 a year. Most health insurance plans do not cover outpatient drugs. According to the Health Care Financing Administration, only 15% of national expenditures on drugs and prescriptions were covered by private insurance in 1987, and another 11% were covered by public programs. Thus 74% of such expenses were out-of-pocket expenses. How many will be able to pay $800~10000 a year, possibly for several years, not to mention other medical expenses connected with such drug treatment? And if these drug costs cannot be paid out-of-pocket by the patients, who will pay? Additional
areas of research
I have discussed the areas of research on the use and costs of medical and support services of persons with AIDS which I regard as having the highest priority. This does not mean that I think they are the only areas that need study. Fitzmaurice noted additional topics, such as the development of better measures of severity of illness, quality of care, and health outcomes, and I agree that these are important topics that should also be studied [17]. Pascal has mentioned the need for more work on converting charge data (which are the most readily obtainable data) to costs to estimate actual resource use by persons with AIDS [18]. (Although, let me point out that studies of the costs of other diseases are generally either based on charge data or, like Dorothy Rice’s, refer to expenditures, which is what we need to compare AIDS costs to total national health care expenditures.) Nor do I want to imply that my priorities are necessarily the right ones - I have submitted them for your consideration and judgement.
Research needs: estimates costs of AIDS
of direct non-personal
and indirect
I shall be very brief on my thoughts regarding research needs in the areas of the and the indirect costs of the AIDS epidemic. When Dorothy Rice and I made our estimates of the direct and indirect costs of AIDS for the CDC, we had serious problems with estimating the direct non-personal costs (even more serious problems than with our estimates of direct personal costs and indirect costs, where we could at least make some assumptions) [19]. Of the areas included under the direct non-personal costs of AIDS, I think the most urgent need for research is on the costs of screening for HIV infection under various scenarios of mandated and personally initiated demand. This follows my earlier comments on the need for studying the demands for treatment by asymptomatic sero-positive persons if prophylactic drug treatment turns out to be promising. This will result not only in increased demand for treatment by this group of the HIV-infected population but very likely also to a very much increased demand for testing by persons who fear they may be infected but did not go for testing when there was no treatment which promised at least an increased life expectancy if not a cure. I would give a study in this area a very high priority. direct non-personal
207
While I would give studies to estimate the indirect costs of AIDS a lower priority than those of the direct medical care costs, they should not be totally neglected. To date, we have no information on the earnings of persons with AIDS or other HIV infections. Rice and I assumed that on balance, they had the same average earnings as others in their age and sex group, because homosexual males probably have somewhat higher than average earnings while i.v. drug-users have lower or no earnings, or earnings from illegal sources. Thus it is desirable to conduct at least some small pilot studies of the earnings of persons with AIDS. If it is found that i.v. drug-users have little or no earnings, or earnings from illegal activities, estimating the indirect costs of morbidity and premature death of this group of AIDS victims will pose ethical rather than economic problems. To sum up, I see plenty of scope for research projects ranging from major national studies to smaller, local studies from which generalizations can be made (for example, on the relative costs of persons treated with AZT - or similar drugs as they get approved by the Federal Drug Administration (FDA) - compared to patients on conventional treatment or other treatment protocols). There is no shortage of talent to carry out such studies. All that is needed are the funds.
References 1 Rice, D.P., Hodgson, T.A. and Koopstein, A.N., The economic costs of illness: a replication and update, Health Care Financing Review, 7 (1985) 61-80. 2 Rice, D.P. and Hodgson, T.A., The social and economic implications of cancer in the United States, Vital and Health Statistics. Series 3, No. 20 (1981) DHHS Publ. No. 81-1401. 3 Hartunian, N.S., Smart, C.N. and Thompson, M.S., The incidence and economic costs of cancer, motor vehicle injuries, coronary heart disease, and stroke: a comparative analysis, American Journal of Public Health, 70 (1980) 12491260. 4 Hay, J.W. and Ernst, R.L., The economic costs of Alzheimer’s disease, American Journal of Public Health, 70 (1986) 1169-1175. 5 American Cancer Society, Cancer Facts and Figures, 1987, (1987). 6 Harris, J., New Estimates of the Incidence of AIDS to 1991, presented at The Johns Hopkins University Conference on AIDS: Research Methodology, Baltimore, MD, September 27, 1988. 7 National Center for Health Statistics; D.A. Dawson and P.F. Adams: Current Estimates from the National Health Interview Survey, United States, 1986, Vital and Health Statistics, Series 10, No. 164, DHHS Publ. No. (PHS) 87-1592. Public Health Service. Washington, U.S. Government Printing Office, October 1987. 8 Dondero, Jr., T.J., Current estimates of HIV prevalence and incidence: sources and data, Health Policy, 11 (1989) 115-124. 9 Dondero, op.cit. 10 Bilheimer, L.T., AIDS cost modeling in the U.S. A pragmatic approach, Health Policy, 11 (1989) 000. 11 Hay, J.W., Econometric issues in modeling the costs of AIDS, Health Policy, 11 (1989) 000. 12 Dondero, op.cit. 13 Andrulis, D.P., Beers, V.S., Bentley, J.D. and Gage, L.S., The provision and financing of medical care for AIDS patients in US public and private teaching hospitals. Journal of the American Medical Association, 258 (1987) 1343-1346. 14 Dondero, op.cit. 15 Seage III, G.R. et al., Medical care costs of AIDS in Massachusetts, Journal of the American Medical Association, 256 (1986) 3107-3109. 16 Arno, P.S., The nonprofit sector’s response to the AIDS epidemic community-based services in San Francisco, American Journal of Public Health, 76 (1986) 1325-1330.
208 17 Fitzmaurice, J.M., AIDS Research Priorities of the National Center for Health Services Research, presented at The Johns Hopkins University Conference on AIDS: Research Methodology, Baltimore, MD, September 27, 1988. 18 Pascal, A., Conceptual framework for modelling the costs of AIDS to society, Health Policy, 11 (1989) 000. 19 Scitovsky, A.A. and Rice, D.P., Estimates of the direct and indirect costs of persons with AIDS in the United States, 1985, 1986 and 1991, Public Health Reports, 102 (1987) 5-17.
11 (1989) 197-208
197
HPE 00264
The cost of AIDS: an agenda for research* Anne A. Scitovsky Health Economics Division, Palo Alto Medical Foundation/Research Institute, Palo Alto, CA, U.S.A. Accepted
31 December
1988
Summary It is generally not appreciated how much we have learned about AIDS in the relatively short time - about 7 or 8 years - since it made its first appearance in the United States. We have learned not only its cause and its way of transmission, but we also have data, though not perfect data, on its incidence and prevalence as well as an increasing body of data on the medical care costs of persons with AIDS. There are few other diseases for which we have as much information on incidence and prevalence, and especially on costs. In addition, various models have been constructed to project the future incidence and prevalence of the disease and the medical care costs associated with it. Nevertheless, serious gaps in our knowledge remain: inadequacies of current data on the number of persons with AIDS and especially on the number of persons infected with HIV; inadequacies and limitations of the data on the medical care costs of persons with AIDS; and an almost total lack of data on the number of persons infected with HIV with symptoms and conditions other than AIDS and their medical care costs. These gaps in our knowledge will be discussed in detail, and various types of studies to fill them will be suggested. AIDS; HIV; Research agenda;
U.S.
*This article is based on a paper presented at the conference, search Methodology’, held at The Johns Hopkins University Baltimore, MD on September 27-28, 1988.
‘The Economic Impact of AIDS: ReSchool of Hygiene and Public Health,
Address for correspondence: A.A. Scitovsky, Chief, Health Economics Division, Foundation/Research Institute, 860 Bryant Street, Palo Alto, CA 94301, U.S.A.
0168-8510/89/$03.50
0
1989 Elsevier
Science
Publishers
B.V. (Biomedical
Division)
Palo Alto Medical
198
1. Introduction In this paper I discuss the many data gaps that still exist with respect to AIDS, and my ideas for an AIDS research agenda. Before doing so, I want to strike a more positive note. It is important to recognise how much work has been done and how much we have learned about the HIV epidemic in the barely 8 years since the disease first made its appearance in the United States. In some respects, we already know as much or more about AIDS than about many other diseases that have been around far longer. To begin with data on incidence and prevalence, we have data on incidence for some major diseases, mainly the various forms of cancer, collected by the American Cancer Society; but we have no data on the prevalence of these conditions. Thus we do not know, for example, how many women with breast cancer are alive at any given time or in the course of a year. Conversely, for the major chronic conditions we have data on prevalence from the Health Interview Survey of the National Center for Health Statistics (NCHS), but we have no data on the incidence of these conditions. Moreover, the data are limited to the civilian, non-institutionalized population and thus omit some important sectors of the population, such as nursing home patients and the military. When it comes to the national costs of other diseases, our knowledge is also rather limited. We have prevalence-based estimates for the 16 broad categories of the International Classification of Diseases (ICD) ( i.e. infective and parasitic diseases, neoplasms, diseases of the circulatory system, etc.) by Dorothy Rice and her colleagues at NCHS [l]. These same researchers have also made prevalencebased estimates of specific cancers by site (16 in all) [2]. Apart from these studies, there are about half a dozen other prevalence-based estimates of various broad groups of conditions - respiratory conditions, musculoskeletal conditions, dementia. Incidence-based estimates of the costs of specific conditions are even rarer. The major work in this area was done in the 1970s by Hartunian et al. on cancer, coronary heart disease, stroke and motor vehicle accidents [3]. More recently (1983), Hay and Ernst did an incidence-based cost estimate of Alzheimer’s disease [4]. Let me add that some of these incidence-based studies estimate aggregate costs only, not lifetime costs per patient. To sum up, our data on the incidence and prevalence of AIDS and of its direct medical care costs compare not unfavorably with corresponding data for other major illnesses, despite the fact that AIDS has a relatively short history compared to these other conditions. AIDS has also received more attention than could be expected on the basis of the number of cases compared to the number of cases of other major illnesses. The incidence of AIDS in 1987 was 22948 and I estimated its prevalence in that year at about twice its incidence, or about 45 900. The CDC estimates its incidence in 1991 at about 70000 cases, which would make its prevalence in that year about 140000, again assuming prevalence to be twice the incidence. The incidence data for various forms of cancer for 1987 (from the American Cancer Society) are as follows [5]:
199
Lung cancer Cancer of the Cancer of the Cancer of the Cancer of the Cancer of the
colon breast prostate urinary system uterus
150 000 145 000 130 900 96 000 67 300 47 800
In other words, the incidence of all but the last two was very much higher in 1987 than the projected incidence of AIDS in 1991, not to mention its incidence in 1987. However, Harris’ estimate of AIDS incidence of 70000 a quarter by 1996 puts the incidence of AIDS higher than the current incidence of any of these diseases, though of course their incidence is also likely to be higher in 1996 than currently [6]. Prevalence data show even greater differences between AIDS and some other conditions. The NCHS Health Interview Survey shows the following prevalence data for 1986 [7]: 9.9 million cases Asthma 6.9 million cases Ischemic heart disease 4.5 million cases Ulcer of the stomach and duodenum 2.0 million cases Emphysema 1.7 million cases Rheumatic fever Thus the prevalence of these conditions currently exceeds Harris’ high estimate of 642000 AIDS cases in 1996. I cite these data on other diseases not to suggest that we have done enough research on the various aspects of the HIV epidemic but to give the AIDS data a frame of reference, some perspective, and to remind us how much has already been accomplished despite the many gaps in our knowledge which require further research. Clearly there are special features of the epidemic which call for special efforts. - AIDS is invariably deadly, with no cure or vaccine currently available nor likely to be available in the near future. - It affects mainly young people, with 67% of all cases in the 20- to 39-year age group and 88% in the 20- to 49-year age group [8]. - It is expensive to treat, though in the absence of lifetime cost data on other major illnesses, it is difficult to estimate where on the cost-per-illness curve it lies. - It has been concentrated in a number of metropolitan areas, with the 10 SMSAs with the largest number of cases accounting for 56% of all cases reported to date (September 5, 1988) and the 20 SMSAs with the largest numbers accounting for 68% of all cases. Even though it is now spreading beyond these centers, they will continue to face the most severe demands on their health care systems [9]. - Last but not least, there is the fear of the disease - it is new, it is infectious, it is deadly, and there is the fear of where it will spread. This element of fear makes it comparable to polio before the advent of a vaccine. It too was a disease which in terms of incidence did not rank high compared to many other diseases but was given a high research priority.
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2. Agenda for research: major gaps in our knowledge After this somewhat lengthy introduction, let me turn to my topic, the major gaps in our knowledge of AIDS which call for further research. My comments fall into 3 broad groups: (1) comments on the models for projecting the incidence of AIDS, and for estimating the costs of AIDS; (2) major data gaps and further research needs for estimating the prevalence of HIV infection and the incidence and prevalence of AIDS; and (3) major data gaps and further research needs for estimating the costs of AIDS and HIV infection in general; most of my comments will focus on this last topic.
Models I have little to say about the models for projecting the number of persons infected with HIV and of AIDS cases. In view of the many uncertainties, it is clear that a variety of models should be used and their results compared. Because the populations at risk are different in different geographic locations, local projections - by state or region - may be better than national projections. I shall also be brief about the models for estimating the medical care costs of persons with AIDS. The Bilheimer model is the more traditional and estimates costs as a function of the major parameters known to affect costs, e.g. geographic location, annual AIDS incidence, risk group distribution, presenting diagnosis, etc. [lo]. The model proposed by Hay uses a medical decision algorithm approach [ll]. Bilheimer recommends her model for estimates on the state level rather than the national level, and I would suggest that Hay’s model should also be used on a subnational level, possibly for a region or even an SMSA. We know that hospital treatment of persons with AIDS differs markedly by geographic area, with hospital length of stay considerably lower in San Francisco than in New York or Boston, and in the West in general compared to other areas of the country. We also know from the work of Wennberg that there are large differences in treatment patterns of specific medical conditions even within relatively small areas. As in the case of the models for projections of the number of AIDS cases, I suggest that both the Bilheimer and Hay models be experimented with, possibly for a state or an SMSA and the resulting cost estimates compared. To sum up, I think we have satisfactory models for estimating the incidence and costs of AIDS. This does not mean that they should not be modified as additional data become available. But they are flexible enough to be adapted to changing circumstances. Our major research needs as I see them, therefore, are not additional models but rather more data to put into the models.
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Research needs: estimates AIDS
of HIV infection
and incidence
of
With regard to estimating the prevalence of HIV infection and the number of AIDS cases in future years, I see several areas that need further study. As Dondero has described, the CDC are planning a two-phased study involving anonymous and confidential blood testing for seroprevalence [12]. The first phase was to be a one-year pilot test in several metropolitan areas beginning last summer (1988) to assess in part whether the response rate is high enough to obtain meaningful results in a broader study. If results look promising, the second phase would survey approximately 50000 households, with results becoming available in 1990. I understand that the first phase of the pilot study, conducted in Washington, DC, last summer, ran into serious problems and that the CDC are now considering attempting the study in some other areas. I see two additional problems with respect to estimating the number of AIDS cases which need further study. One is the problem of under-reporting. The Centers for Disease Control (CDC) have estimated that under-reporting of AIDS cases may be as high as 20%. However, I suspect that this under-reporting is not uniform across risk groups and areas, and especially that AIDS cases who are iv. drugusers may be under-reported to a greater extent than homosexual males. If this is the case, under-reporting is a special problem in the areas where i.v. drug-users are concentrated, by and large the Northeast, and in particular the New York-Newark and Jersey City-New Jersey areas. If these centers, whose medical resources are already under severe strain, are to make plans for providing services for future AIDS cases, it is essential to assess the extent of under-reporting in their service areas. We also need data on the number of cases with the conditions added to the CDC definition of AIDS last year, the so-called ‘wasting syndrome’ and dementia. To date, the CDC have not listed figures for these two new conditions separately in their AZDS Weekly Surveillance Reports but apparently include them with ‘other opportunistic diseases’. In addition to better data on the incidence of AIDS, we also need data on other HIV-related conditions short of full-blown AIDS, conditions which in the past have been referred to as AIDS-related complex (ARC). There are no data on the number of ARC cases, but they have been variously estimated at 2 to 5 or 6 times (and up to 10 times) the number of AIDS cases. Nor are there any data on their life expectancy or number of months or years from diagnosis to death or conversion to AIDS. To obtain data on these cases, a definition of the conditions covered by this group of less-than-full-blown AIDS is needed, as well as cohort studies to determine the length of time patients live with these conditions before converting to AIDS or dying.
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Research needs: estimates of the direct personal health care costs of persons with AIDS Nationwide
cohort studies of AIDS
This brings me to data gaps and research needs with regard to estimating the medical care costs of persons with AIDS. The empirical studies conducted to date, with one exception (Andrulis’ study of AIDS patients treated in public and private teaching hospitals [13], have been limited to a few geographic areas - San Francisco, New York and Massachusetts. In addition, most are limited to inpatient hospital services or at best to inpatient and outpatient hospital services. All of them have been retrospective, so that their data are likely to be somewhat outdated by the time they were completed, considering how fast treatment of AIDS is changing. Finally, the studies used different methodologies of data collection and analysis. For all these reasons, they do not provide a good basis for even rough estimates of the national costs of AIDS. Under a contract with the National Center for Health Services Research (NCHSR), my research team (consisting, in addition to my co-workers at the Palo Alto Medical Foundation, of experts from SRI International, University of California San Francisco and New York University) has developed a research protocol for conducting a nationwide study of the costs of the medical, social and support services of persons with AIDS. The study would consist of prospective studies conducted at 8 geographic sites, in which cohorts of persons with AIDS would be followed for one year and all data on their use and costs of services collected from or on behalf of them. While the study will still not provide the basis for a statistically unbiased estimate of the national costs of AIDS, it will provide much better data for at least approximate estimates because it is a prospective study, covers representative geographic areas (and within each site, representative providers of care), obtains more complete data than previous studies, and last but not least uses a uniform methodology of data collection and analysis. This kind of study is expensive. It would be interesting, therefore, if parallel studies were conducted in 2 or 3 of the NCHSR sites using Hay’s medical decision algorithm approach and the results of the two approaches compared. If the results were similar, one could possibly use his method in the future at least in part as a substitute for the cohort studies. I say ‘in part’ because I doubt that the algorithm approach can capture all the social and support services persons with AIDS rely on. I also want to repeat that they should be used for local (State or metropolitan) rather than national estimates. In addition to the need (as I see it) for a comprehensive nationwide study of the costs of AIDS, there are areas for further research, which the nationwide study will either not cover at all or cover only partially. Data on costs of special groups
There is, first of all, the problem of the costs of care of special groups of persons with AIDS. The studies conducted to date have been predominantly of homosex-
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ual males. It is generally assumed that persons with AIDS who are i.v. drug-users have higher medical care costs than homosexual males, primarily because they are more likely to present with Pneumocystis carinii pneumonia (PCP), which is more expensive to treat than Kaposi’s sarcoma (KS), a presenting diagnosis more common among homosexual males. However, there are no conclusive data on possible cost differences between the two groups. An unpublished report by the New York State Department of Health some years ago found no difference in the average length of hospital stay and average charge per hospital day between persons with AIDS who were i.v. drug-users compared to all others with AIDS. Moreover, the CDC data indicate that the relative importance of KS as a presenting diagnosis has been declining. In 1987, through September 7, 10% of all newly reported cases had a presenting diagnosis of KS. During the same period in 1988, the percentage had dropped to 6%. Even in absolute terms, the number of newly reported KS cases in 1988 (through September 5) was only 9% more than during the same period in 1987, while the number of cases reported with PCP rose by 45% and that of other opportunistic diseases almost tripled. This change in the distribution of cases by presenting diagnosis may be due to the increase in the percentage of new i.v. drug-user cases from 15% in 1987 (through September 7) to 24% in 1988 during the same period. But the data are not conclusive. Thus data on the use and costs of services of this group are presently lacking and need special study. The proposed national study will provide some data for this group, but possibly some additional local studies with larger samples of i.v. drug-user AIDS cases are necessary . Women and children with AIDS are another group for whom no cost data are available. The percentage of new cases of women with AIDS has risen from 7% in 1987 (through September 7) to 10% in 1988 (through September 5), that of new pediatric cases from 1.3% in 1987 to 1.8% in 1988. [14]. It is possible that the costs of female AIDS patients are similar to those of males, but pediatric cases very likely have different treatment and cost patterns. They are likely to have longer hospital stays because it seems many of their mothers have either died of AIDS or abandoned them. In addition, they are difficult to place in foster homes. Because about one-third of the pediatric cases are in New York City, this would be a good site for a pilot study. Data on payers of care
Second, there is the lack of data on payers of care and amounts paid by different payers. While some of the studies conducted to date indicate ‘expected source of payment’ or even average cost per patient by type of insurance coverage (e.g. Seage’s 1984 Massachusetts study) [15], there are no good data for estimating the distribution of total national costs by source of payment. An AIDS patient’s insurance status is likely to change over his or her lifetime: he/she may start with private insurance, go to self-pay when he/she can no longer work and loses insurance coverage, and finally qualify for Medicaid if he/she has spent down to Medicaid eligibility levels or, if he/she lives long enough, may qualify for Medicare un-
204
der the Social Security Disability Insurance program which requires a two-year waiting period. This latter possibility is becoming more likely as life expectancy of persons with AIDS increases. Thus the best way to obtain good data on the distribution of costs by source of payment is probably by cohort studies of representative groups of AIDS patients. I know from my own past cost-of-illness studies that this is time consuming and costly. Patients often do not know who paid how much for what, and Medicaid patients do not know at all how much was paid on their behalf. Thus it would be helpful to get data also from third-party payers. To date, however, neither Medicaid data nor data from insurance companies and the Blues have been very useful, although they are all now making efforts to improve their AIDS data. Efforts should therefore be made to collect and evaluate these data as they become available and to use them as the basis for estimating the distribution of the costs of care by principal payers. Data on services provided
by volunteers
and families of persons with AIDS
A third important area for further research is a comprehensive survey of the amount and kinds of social and support services provided to persons with AIDS by volunteers and the patient’s lovers and families. Arno has done some very valuable work on this subject, but it needs wider study [16]. It is well known that costs of AIDS in San Francisco have been held down by the network of community support systems which were organized largely by the gay community and staffed to quite an extent by volunteers. This has enabled AIDS patients to be discharged sooner from the hospital or in some cases be taken care of at home and avoid hospitalization altogether. Other metropolitan centers have made efforts to adapt this so-called ‘San Francisco model’, I do not know with what success. I believe this subject should have a high priority for research. We have to know the types and amounts of services currently being provided by volunteers not only because such data are of general interest currently but also for making plans for the future. I doubt very much that in centers like New York, where a high percentage of persons with AIDS are i.v. drug-users, the San Francisco model can be duplicated. Moreover, it may not function indefinitely even in San Francisco. Not only is the supply of volunteers unlikely to keep up with the increase in the number of cases expected in the next few years, but even some of the current volunteers may ‘burn out’ or come down with AIDS themselves. The same is true for lovers and family members of persons with AIDS. If paid personnel will eventually have to be substituted at least in part for volunteers and family members, the sooner we have data on the basis of which to estimate the number and type of paid personnel who will eventually have to take over the better. Data on costs of new medical treatments
and methods
of delivering
care
To date there are no data on the costs associated with new medical treatments, notably the use of AZT. We have done a very small pilot study at San Francisco General Hospital which suggests that in the first 12 months of treatment with AZT,
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AZT patients have significantly lower hospital costs and also lower total costs than a matched group of AIDS patients on conventional treatment. Let me stress that it is a small study. But even if the findings are proved correct by other studies (however, I do not know of any other studies), this is not conclusive because the data are for the first 12 months only and did not cover AZT patients to death because none of the patients on AZT died in the first 12 months while the patients not on AZT all died. Thus we do not yet have data on the lifetime costs of patients on AZT, whose terminal care costs may be as high as those of other persons with AIDS. I suggest that in future Phase 2 drug trials, a use and cost data collection protocol be incorporated from the beginning. Similarly, there are no data yet on the possible cost savings of new models of delivering care to persons with AIDS, such as case management. I trust that the Robert Wood Johnson Foundation and Health Resources and Services Administration (HRSA) demonstration projects will be carefully evaluated to shed light on this subject, and I hope that additional studies in this area will be undertaken. Data on HIV-related
conditions
other than AIDS
So far, I have limited my discussion to research needs on the costs of AIDS. But we also need some studies of the costs of the conditions which used to be classified as ARC. To date, we have some data from the 1987 California Health Department’s Medical study which estimates the monthly Medical costs of a person with ARC at about $652, or about 27% of the monthly costs of a person with AIDS. But in the absence of data on the length of time a patient lives with ARC (before either dying or converting to AIDS), no estimates of lifetime costs are available. Data on medical care use and costs of asymptomatic
HIV-infected
persons
Finally, I suggest that we begin some research as soon as possible on the medical care use and costs of asymptomatic (or mildly symptomatic) HIV-infected persons. Their current use of health services is probably relatively small, though there is some evidence that the ‘worried well’ in the general population account for quite a large share of health care expenditures; and there is every reason for members of the groups at risk of HIV infection to be among the ‘worried well’. But my reasons for this suggestion are not so much getting information on their current use of medical services as to provide a basis for estimating their future use. If current small-scale experiments with treating asymptomatic HIV-infected persons with drugs such as AZT to delay or possibly even prevent progression to AIDS prove promising, I expect a large increase in the demand for such treatment, for which we are not prepared at this stage, either in terms of the necessary resources especially in the metropolitan centers where AIDS is already causing a major strain on their health care system, or in terms of financing such care. The financing problem is especially intricate. Such persons are presumably not sick and, if they have jobs, can continue to work and in most cases continue to be covered by their health insurance plans. But drug costs (if they are like ‘those of
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AZT) are high - AZT costs between $8000 and $10000 a year. Most health insurance plans do not cover outpatient drugs. According to the Health Care Financing Administration, only 15% of national expenditures on drugs and prescriptions were covered by private insurance in 1987, and another 11% were covered by public programs. Thus 74% of such expenses were out-of-pocket expenses. How many will be able to pay $800~10000 a year, possibly for several years, not to mention other medical expenses connected with such drug treatment? And if these drug costs cannot be paid out-of-pocket by the patients, who will pay? Additional
areas of research
I have discussed the areas of research on the use and costs of medical and support services of persons with AIDS which I regard as having the highest priority. This does not mean that I think they are the only areas that need study. Fitzmaurice noted additional topics, such as the development of better measures of severity of illness, quality of care, and health outcomes, and I agree that these are important topics that should also be studied [17]. Pascal has mentioned the need for more work on converting charge data (which are the most readily obtainable data) to costs to estimate actual resource use by persons with AIDS [18]. (Although, let me point out that studies of the costs of other diseases are generally either based on charge data or, like Dorothy Rice’s, refer to expenditures, which is what we need to compare AIDS costs to total national health care expenditures.) Nor do I want to imply that my priorities are necessarily the right ones - I have submitted them for your consideration and judgement.
Research needs: estimates costs of AIDS
of direct non-personal
and indirect
I shall be very brief on my thoughts regarding research needs in the areas of the and the indirect costs of the AIDS epidemic. When Dorothy Rice and I made our estimates of the direct and indirect costs of AIDS for the CDC, we had serious problems with estimating the direct non-personal costs (even more serious problems than with our estimates of direct personal costs and indirect costs, where we could at least make some assumptions) [19]. Of the areas included under the direct non-personal costs of AIDS, I think the most urgent need for research is on the costs of screening for HIV infection under various scenarios of mandated and personally initiated demand. This follows my earlier comments on the need for studying the demands for treatment by asymptomatic sero-positive persons if prophylactic drug treatment turns out to be promising. This will result not only in increased demand for treatment by this group of the HIV-infected population but very likely also to a very much increased demand for testing by persons who fear they may be infected but did not go for testing when there was no treatment which promised at least an increased life expectancy if not a cure. I would give a study in this area a very high priority. direct non-personal
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While I would give studies to estimate the indirect costs of AIDS a lower priority than those of the direct medical care costs, they should not be totally neglected. To date, we have no information on the earnings of persons with AIDS or other HIV infections. Rice and I assumed that on balance, they had the same average earnings as others in their age and sex group, because homosexual males probably have somewhat higher than average earnings while i.v. drug-users have lower or no earnings, or earnings from illegal sources. Thus it is desirable to conduct at least some small pilot studies of the earnings of persons with AIDS. If it is found that i.v. drug-users have little or no earnings, or earnings from illegal activities, estimating the indirect costs of morbidity and premature death of this group of AIDS victims will pose ethical rather than economic problems. To sum up, I see plenty of scope for research projects ranging from major national studies to smaller, local studies from which generalizations can be made (for example, on the relative costs of persons treated with AZT - or similar drugs as they get approved by the Federal Drug Administration (FDA) - compared to patients on conventional treatment or other treatment protocols). There is no shortage of talent to carry out such studies. All that is needed are the funds.
References 1 Rice, D.P., Hodgson, T.A. and Koopstein, A.N., The economic costs of illness: a replication and update, Health Care Financing Review, 7 (1985) 61-80. 2 Rice, D.P. and Hodgson, T.A., The social and economic implications of cancer in the United States, Vital and Health Statistics. Series 3, No. 20 (1981) DHHS Publ. No. 81-1401. 3 Hartunian, N.S., Smart, C.N. and Thompson, M.S., The incidence and economic costs of cancer, motor vehicle injuries, coronary heart disease, and stroke: a comparative analysis, American Journal of Public Health, 70 (1980) 12491260. 4 Hay, J.W. and Ernst, R.L., The economic costs of Alzheimer’s disease, American Journal of Public Health, 70 (1986) 1169-1175. 5 American Cancer Society, Cancer Facts and Figures, 1987, (1987). 6 Harris, J., New Estimates of the Incidence of AIDS to 1991, presented at The Johns Hopkins University Conference on AIDS: Research Methodology, Baltimore, MD, September 27, 1988. 7 National Center for Health Statistics; D.A. Dawson and P.F. Adams: Current Estimates from the National Health Interview Survey, United States, 1986, Vital and Health Statistics, Series 10, No. 164, DHHS Publ. No. (PHS) 87-1592. Public Health Service. Washington, U.S. Government Printing Office, October 1987. 8 Dondero, Jr., T.J., Current estimates of HIV prevalence and incidence: sources and data, Health Policy, 11 (1989) 115-124. 9 Dondero, op.cit. 10 Bilheimer, L.T., AIDS cost modeling in the U.S. A pragmatic approach, Health Policy, 11 (1989) 000. 11 Hay, J.W., Econometric issues in modeling the costs of AIDS, Health Policy, 11 (1989) 000. 12 Dondero, op.cit. 13 Andrulis, D.P., Beers, V.S., Bentley, J.D. and Gage, L.S., The provision and financing of medical care for AIDS patients in US public and private teaching hospitals. Journal of the American Medical Association, 258 (1987) 1343-1346. 14 Dondero, op.cit. 15 Seage III, G.R. et al., Medical care costs of AIDS in Massachusetts, Journal of the American Medical Association, 256 (1986) 3107-3109. 16 Arno, P.S., The nonprofit sector’s response to the AIDS epidemic community-based services in San Francisco, American Journal of Public Health, 76 (1986) 1325-1330.
208 17 Fitzmaurice, J.M., AIDS Research Priorities of the National Center for Health Services Research, presented at The Johns Hopkins University Conference on AIDS: Research Methodology, Baltimore, MD, September 27, 1988. 18 Pascal, A., Conceptual framework for modelling the costs of AIDS to society, Health Policy, 11 (1989) 000. 19 Scitovsky, A.A. and Rice, D.P., Estimates of the direct and indirect costs of persons with AIDS in the United States, 1985, 1986 and 1991, Public Health Reports, 102 (1987) 5-17.