Donor Deferral Registries

Donor Deferral Registries William C. Sherwood

HE INTEREST to interdict selectively individuals from donating blood occurred in the initial years of transfusion history when the fulI extent of hepatitis transmission and its carrier state became known. During this early era, donor history and donor deferral registries were the only methods at hand to protect blood supply safety. Although there remained a significant risk of hepatitis associated with blood transfusion, intense public and regulatory interest in transfusiontransmitted infections did not occur until the emergence of human immunodeficiency virus (HIV) in the early 1980s. Rosters, or registries, of deferred individuals began with simple lists of names, often maintained as card files. Usually, these lists were smalI extracts of donor bases of organizations collecting blood and were easy objects for manual search at the time of donor registration. "Deferral" has been used as a convenient term to bar the welI-meaning, altruistic individual without the accusation of a disease state when it was uncertain that one existed. Even the often-used term "indefinite deferral" implies a temporary status even when that is not usually the intention. Today, there are many methods in place that are intended to provide increased safety to the blood supply. Of all of the methods used, serological testing has emerged as the only technique that is exclusively objective. Data accumulated on the value of serological testing have demonstrated its enormous benefit. 1-4 Significant declines in transfusion-associated infection can be correlated with the introduction of specific testing. 3 •5 •6

T

SUBJECTIVE VERSUS OBJECTIVE METHODS

In addition to the donor deferral registry other subjective methods in use to protect the safety of the blood supply include the donor health history, a limited donor physical examination, confidential unit exclusion, and the use of volunteer donors. For most blood colIection organizations the donor history has been expanded to include many associations of infectious disease exposure, including explicit questioning about the social behavior and sexual practices of donors. 7 ,8 As the reasons for donor deferral have markedly expanded, donor Transfusion Medicine Reviews, Vol VII, No 2 (April), 1993: pp 121-128

deferral registries have been broadened far beyond the early index card file to include large lists of donor-identifying information in multiple categories, published as voluminous listings or files managed by computer systems. There are some objective components to most donor deferral registries. These include the listing of donors that have demonstrated previous positive (reactive) test results. However, the major portion of donor deferral registries is usualIy comprised of categories that contain subjective information obtained from the donor during the health history interview. The subjective methods used to screen blood donors cast a wide but imperfect net. The sensitivity as welI as the specificity of these methods, in comparison to serological testing, seems inferior. However, increasing the sensitivity of these methods by widening the deferral policies in an attempt to include more "dangerous" donors reduces the specificity and defers many more "safe" donors. An increase in the already large numbers of deferred donors must be weighed against the need for blood and the frequency of precarious blood inventories. As the subjective methods have expanded there has been the attempt to balance the benefit of aggressively widening donor deferral policies against the risk of diminishing the available blood supply below reasonable clinical needs. In recent years there has been a shift in the manner in which the subjective methods are characterized. Frequently, they are viewed as methods to close the gaps where testing methods may fail, such as the "window period" between exposure to a transmissible virus and serological conversion. 9 •1O As testing sensitivity improves, the relative value of these subjective methods seems to diminish. If clinical testing were perfect or even near perfect, the subjective methods would be unnecessary. From the American Red Cross Blood Services, Penn Jersey Region, Philadelphia. PA. Address reprint requests to William C. Sherwood, MD, Senior Principal Officer, American Red Cross Blood Service, Penn Jersey Region, 23rd and Chestnut Sts, Philadelphia. PA 19103.

Copyright © 1993 by W.B. Saunders Company 0887-7963/93/0702-0006$3.00/0

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WILLIAM C. SHERWOOD

For most of the subjective methods in use, ineluding donor deferral registries, there is very little available data on which to draw conelusions concerning either their relative or absolute value in protecting the safety of the blood supply. Moreover, because of the great increase in safety attained with current testing, perforrning any analyses of the subjective methods used before the testing era would only be of historical interest. This change has raised a fundamental question for blood collection organizations and regulatory agencies: which of the subjective methods used in the donor screening process remain of value? Are some of the methods in use, because of the introduction of specific testing, of such little value that they are only ceremonial? This question is important because their reinstatement would return many otherwise safe donors to the blood donor pool. In addition, the elimination of such practices will allow greater focus on those methods that have a proven value. REGULATIONS AND STANDARDS

The current Food and Drug Administration (FDA) regulation requires that "A record shall be available from which unsuitable donors may be identified so that products from such individuals will not be distributed." 11 This mandate leaves room for broad interpretation. Furtherrnore, it is not elear if this requirement extends to the donor as well as to the product safety. This FDA regulation seems to suggest that it is acceptable to collect blood from donors that are unsuitable because of donor safety, as long as the products produced are not distributed, even though they may not be of increased risk to the recipient. Some blood collection organizations maintain historical files of donors that require deferral because blood donation presents a risk to their health. Cardiovascular disease is one such example. It is the intention of this type of registry to assure that these donors will be deferred if they return to donate and deny the disqualifying history. The difficulty associated with assuring accurate donor identification and maintaining updated donor biographic inforrnation and donation status in donor deferral registries has created a major challenge for blood collection organizations to remain in strict compliance with FDA regulations. Donors imprecisely entered into deferral regis-

tries who continue to attempt to donate and present subsequent "normal" health histories and viral testing are particularly challenging. They are likely to be missed during ensuing deferral registry screening. Such instances are in violation of FDA regulations and may result in the erroneous release of products that are subject to recall when the error is discovered. Such errors may not be detected for months or years after they occurred, leading to a recall of many products that have long since been transfused. For compliance purposes, the distribution of such products must be considered as erroneous release and any increased risk to the recipient is debatable, particularly when more highly valued viraI testing results were negative at the time of collection. The current Standards for Blood Banks and Transfusion Services published by the American Association of Blood Banks do not directly address the issue of deferral registries. Appropriately, these standards require certain perrnanent and temporary deferral policies as well as the retention of certain records. 12 However, they do not specify how such deferrals are to be perforrned. There is the presumption that deferral registries are in place and used by those organizations that collect blood. CONTENT OF DONOR DEFERRAl REGISTRIES

Deferred donors are placed in blood donor deferral registries for several basic reasons, ineluding (I) previous abnorrnal testing, (2) a previous disqualifying health history, (3) a previous donation associated with a transfusion infection, or (4) names of persons with known infection or risk factors contributed by local or state agencies. As noted, donors that have given a disqualifying history may be entered into a registry to try to prevent transmission of that infection to a recipient or, al· ternatively, to prevent blood donations from indi· viduals that may be harmed by the procedure because of a health disorder. In the United States, recent experience with the management of large numbers of autologous donors has indicated that there are very few conditions in which blood donation could not be considered safe. 13 ,14 Most blood donor registries contain only entries for donors that are exeluded because of a potential risk to the recipient. These registries rely on the donor with medical condi-

DONOR DEFERRAL REGISTRIES

tions who might be injured by blood donation to give a consistent health history on return. The American Red Cross (ARC) donor deferral registry15 is comprised of a nationwide list of approximately 300,000 entries. An additional component to this registry remains exclusively local to regional bIood centers. If alI were collated into one file, nationaI and Iocal, the ARC registry wouId contain approximateIy 1.6 million entries. These data suggest that there may be approximately 3 million entries in such registries, representing approximateIy 1% of the popuIation in the United States. This is a maximum estimate and does not account for overlap among registries. The size of the ARC donor deferraI registry and its computerization has precluded its use before donation at mobile blood collection sites. As a resuIt, unlike smaller registries, it is used after blood collection when donor units and donor information have been retumed to the bIood center. It should be apparent that such registries can not be used to prevent donations that may be of potential harm to the donor. In the future, increased data storage capabilities of small portable computers might make it possible to manage even the largest of deferral registries at alI blood collection sites. TabIes 1 and 2 list the deferral reasons for the national and local ARC donor deferral registry and illustrate the complexities associated with these registries. 15 The reasons depicted here comprise 20 different categories of the registry. Some categories are merely holding, or "silent, " sections of the file used to keep donor entries that have exhibited a previous abnormality: however, such donors are not deferred until a second abnormality occurs. Donors that are associated with transfusionassociated hepatitis from muJtiple units are placed into one of these categories and move to a deferred category if a repeat association occurs on subsequent donations. To add to the intricacy, many donor deferrals are temporary. Such donors become eligible to donate again after a specified period of time. These temporary deferral periods vary and depend on the circumstance. For example, the deferral period for immigrants from an area endemie for malaria is 3 years, whereas for visitors retuming from these areas it is 6 months if prophylaxis has not been taken or 3 years if it has been taken. There are some categories in which the donor is silently listed in the registry, but becomes deferred

123 Table 1. Donor Defetral Categori_Health Hi_tory Oisease

Health History

Hepatitis

Hepatitis after age 10. Seleeted hepatitis riskexposures ineluding blood transfusion. Implieated in reported transfusion-assoeiated hepatitis, one unit. Implieated in reported transfusion-assoeiated hepatitis, multiple units, one time. Implieated in reported transfusion-assoeiated hepatitis, multiple units, twiee. AIDS or eonfirmed positive anti·HIV test. High-risk behavior for AIDS, maJe/male sex, street drugs. Limited risk behavior for AIDS, sex with a prostitute, syphilis, gonorrhea. Malaria. Immigration from an endemie area. Following visitation to an endemie area, no prophylaxis. Following visitation to an endemie area, with prophylaxis. Chagas' disease, ehronie Lyme disease, babesiosis, Creutzfeld-Jaeob disease, human pituitary growth hormone use. Visit to Persian Gulf. Medieal Director diseretion.

AIDS

Malaria

Other

Abbreviation: AIDS,

aeąuired

Deferral

Indefinite 12 mo

Indefinite

May donate, holding file Indefinite

Indefinite Indefinite

For 12 mo after exposure 3 yr 3 yr 3 yr

6 mo

Indefinite

Until 1/93 Variable

immunodefieieney virus.

when a later but different event occurs, ie, the donor with a repeatedly reactive HBsAg test, which is nonneutralizable by the confrrrnatory test, and with a negative anti-HBc test remains eligible to donate but becomes indefinitely deferred if the anti-HBc test subsequently becomes repeatedły reactive. Without the nonneutralizable HBsAg event the donor would not be deferred until two consecutive, repeatedly reactive anti-HBc tests occurred. The rules for donor deferral registries are constantly changing, requiring almost continuous change of existing systems and retraining of per-

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WILLIAM C. SHERWOOD Table 2. Donor Deferral Categories-Testing Results Test

HBsAg

Anti-HIV

Anti-HCV

Anti-HBc Anti-HTLV 1111

Alanine aminotransferase

Results

Oeferral

RR for HBsAg and confirmed by neutralization RR for HBsAg and unconfirmed and RR for anti-HBc RR for HBsAg and unconfirmed on two occasions RR for anti-HIV Y, and confirmed by WB RR for anti-HIV 2 RR for anti-HIV Y, and indeterminate WB and fai led reentry RR for anti-HIV Y, and negative WB and NR anti-HIV 2 RR for anti-HCV and confirmed RR for anti-HCV and unconfirmed, once RR for anti-HCV and unconfirmed, twice RR for anti-HBc, once RR for anti-HBc, twice RR for anti-HTLV 1111 and confirmed RR for anti-HTLV I/II and unconfirmed, once RR for anti-HTLV 1111 and unconfirmed, twice Greater than lower, less than upper cutoff, once* Greater than lower, less than upper cutoff. twice* Greater than upper cutoff*

Indefinite Indefinite Indefinite Indefinite Indefinite Indefinite Temporary, may reenter Indefinite May donate, holding file Indefinite May donate, holding file Indefinite Indefinite May donate, holding file Indefinite May donate. holding fil!! Indefinite Indefinite

Abbreviations: RR, repeatedly reactive; WB, Western blot; NR, nonreactive; HBsAg, hepatitis B surtace antigen; anti-HBc hepatitis B core antibody. * Lower cutoff 60 lU; upper cutoff 100 lU.

sonnel. At times, even overhauls of data bases and changes to their fundamental structure are necessary. These features demonstrate the challenges associated with current requirements for donor deferral registries. For all but the smallest registries, computers are necessary for their practical management. However, even the most automated systems require considerable manual interaction and judgement. For those who are familiar with these systems, it is not surprising that errors have occurred, even with the most attentive management. DONOR IDENTIFICATION

Accurate and consistent identification of the donor is a key factor in the optimum use of donor deferral registries and represents the most difficult challenge. This issue confronts the reality that people often change their name (marriage), address, and other identifying information. They may not have accurate documentation available when presenting at collection sites, may not remember characteristic identification numbers, such as their sociał security number, or ałtematively, they may present erroneous information inconsistently each time they appear. Adonor listed in the registry who presents differing identifying information that remains unrecognized may donate repeatedły, resulting in a product that is release and transfused. Computer-

ized deferral registries may be particularly vulnerable, because a simple error such as a transposed character may cause the donor to be missed by the system. An important part of this problem is represented by donors that may be listed in deferrał registries more than once, each entry having a different attribute listed in the record, including different reasons for deferral. These dupłications are of concero if they are unnoticed. Donors entered in the registry for permanent reasons may be removed or overlooked when a temporary entry from the same donor is removed. Some organizations have developed additional computer applications to be applied to deferral registry files on a continuing or periodic basis as "utilities" to recognize duplicate or discrepant records. The most effective time to establish accurate identity is when confronting the donor at the blood collection site. Here, identifying information can be requested and discrepancies can be reconciled with the donor at hand. Common methods in use to identify the donor at blood collection site are presented in Table 3. A practical method that will accurately identify each donor on every occasion that they present has yet to be devised. Although there are considerable technical advances in the identification of people, such as automated finger print or retinal matching, such methods are still cumbersorne and expensive,

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DONOR DEFERRAL REGISTRIES Teble 3. Methods of Donor Identlficetion Used et Blood Collection Sites Combination of donor biographic information name, address, zip code, birth date. Social security number. Unique identifying number assigned by blood collection agencies to repeat donors. Presentation of selected documentation: Driver's license, Blood donor card, Employee/student identification card, Birth/baptismal certificate, Passport. Photo identification.

eliminated. Names that do not contain enough consonants to code three digits are filled out with zeros (Lee would be Loo). Names that contain more consonants than can be coded in three digits are truncated and the trailing consonants are not represented in the code (McGillicutty would be M242). This method places every name in one of 26,000 possibłe codes (26 x 1,000). Some examples of soundex codes are presented in Table 5. Teble 5. Soundex Exemples of Surnemes Name

and may not be realistic for mobile unit environments in which 70% of the blood in North America is collected. 16 However, they show promise for the future.

O'Brien Kane Faye Oppenheimer Phillips

Letters Coded

b,r,n n p,n,m I,p,s

Code No.

0165 K500 FOO 0155 P412

SOUNDEX

To manage files that may contain duplicate or discrepant records, methods have been developed to make comparisons and analyses of names that sound the same but, intentionally or inadvertently, are spelled differently, eg, Smith, Smythe, Smeith, etc. Such discrepancies may become legion as files with names and biographic information grow in size. This issue was addressed as early as the 1880 census records by a method of name indexing termed soundex. 17 The purpose of this indexing is to group names that sound alike by a numerical code, a process that is very computer friendly. The standard and earliest soundex method in use provides a code for each sumame represented by the first letter of the name folIowed by three numerical digits. Each digit of the code represents a consonant from a grouping of one or more letters that, in the context of a word, may sound alike (Tabłe 4). Teble 4. Classie Soundex Codes Code Number

Key Consonant Groups

1 2

b,p,f,v c,s,k,Q,j,q,x,z d,t I m,n

3 4 5 6

The vowels a, e, i, o, u, and y, and the consonants wand h are eliminated from the coding process. Double letters can be represented by only one digit and name prefixes (van, Von, de) are usually

A number of organizations and computer firms have developed similar soundex systems to accommodate speciał needs and today many variations are in place. These variations have been developed to accommodate areas that have a commonality of names or to control the range of possible narnes that may occur in each code. The more liberal coding methods accumulate more names into fewer codes. With the need to detect as many duplicate and discrepant donor file entries as possible, the more liberal soundex coding methods are the methods of choice. However, they will require more manuał effort to reconcile potential duplications. The value and the focus of soundex for donor files can be greatly enhanced when combined with other methods or donor characteristics. When searching a file for potential duplicate donors using soundex names, the numbers of potential duplicates to be reconciled can be halved if the sex of the donor is also used. Even greater focus can be achieved if birth date (or range of birth dates) is added. Zuck has developed a system for donor file management for which a blood collection organization can choose the degree of search precision desired by selecting from a range of donor characteristiCS. 18 Four key characteristics of the donor are used; a soundex version of the donor narne, donor address, birth date, and social security number. Using a statistical probability method, each characteristic inserted in the formula contributes to the cumulative precision of the task and/or size of the

126

WILLIAM C. SHERWOOD

search net cast. As in serological testing, matches are treated as "initial reactives" until manually reconciled. Confirmation of the match converts this status to "repeatedly reactive." FILE STANDARDIZATION

Although obtaining accurate donor identifying information is a cńtical requirement for data integńty of deferral registńes, it is not the only controlling one. Often, donor deferral registńes are compiled from data received from multiple locations or multiple agencies. Some states maintain lists of high-ńsk individuals that are required to be used duńng the donor screening process. Usually, these lists contain many nondonors as well as donors. The nondonor record is less likely to have search key information needed to perform effective automated searches. Records in the donor registry file with blank or missing key search information are of little value. In such states blood collection agencies may find it necessary to screen the state registry in addition to their own in separate steps. For such reasons, standardization of the methods used for the donor deferral file would be most useful. This elaboration on donor identity and file management is more than a pedantic exercise. In recent years one of the most common blood banking problems, necessitating the recall of distńbuted products, has resulted from duplicate or discrepant entńes to these files. This problem must be balanced with the reality , given the size of these files (1.2 million donor records in the ARC Penn Jersey Region alone) and the foibles involved in obtaining biographic information from the donor that perfection of the files or the search method is not practicably obtainable. In addition, clinically, the problem is moderated by the lack of evidence of disease ńsk for products transfused from donations that cleared serological testing but should have been detected by adonor deferral registry. THE VALUE OF DONOR DEFERRAL REGISTRIES

As noted, there are only meager data available that illustrate either relative or absolute current value for the subjective methods used for blood supply safety. The value of the volunteer versus the paid donor has not been carefully examined since the implementation of the many transmissible disease tests currently in use. 19- 22 The problem of obtaining data to determine the

value of deferral registńes is compounded by the considerable overlay of subjective methods and the inability to perform definitive studies. Certainly, the intentional transfusion of blood from donors listed in deferral registńes to observe recipient outcome cannot be performed. Although the inadvertent release and transfusion of blood products collected from donors listed in the registry has occurred, there are not enough data to draw definitive conclusions. The evaluation of these methods is left to indirect techniques, all of which have weaknesses. The method that has received widest use is the evaluation of serological markers for the donor population under study. 23.24 A demonstration of enńch­ ment or lack of enńchmentof markers is presumed to provide an objective analysis of relative safety when compared with the routine donor population. The serological markers that may be evaluated include the confirmed tests for HBsAg, the serological test for syphilis, anti-HIV-1 and -2, alanine aminotransferase, anti-HBc, anti-human T-cell lymphotropic virus 1111, anti-hepatitis C virus, and anti-cytomegalovirus. Because units of blood that test positive will be discarded, these studies presume that blood that tests negative, which is collected from groups that have enńched marker rates, will be at greater ńsk than blood that tests negative, which is collected from the random donor population. Such data must be interpreted with caution because, although theoretically probabIe, there is no data to substantiate the premise. Nor are there data to suggest that the degree of ńsk is at all related to the degree of marker enńchment. Among the selected donor populations that have been evaluated in this manner are paid donors,20.21 frrst-time donors,24 autologous donors,25 directed donors,26 and confidential unit exclusion donors. 27 .28 The use of marker rates to evaluate the relative safety of nondonor populations as compared with donor populations seems to be of little value. The donor population has expeńenced multiple additional screening procedures that tend to invalidate a comparison with groups of nondonors. There are multiple components to the question as to the value of donor deferral registńes. These include the value of each category of the registry and the value of increasing geographic scope of the registry. Of the Iatter, is a nationaI or wide-area registry worth the enormous increase in effort over the exclusive use of Iocal registńes? There are no

127

DONOR DEFERRAl REGISTRIES

published studies that have evaluated these questions. The ARC Blood Centers, distńbuted throughout the United States, eontńbute to a single central registry for some eategońes of deferred donors and roaintain only loeal registńes for other deferral eategońes. An evaluation of this early eomputeńzed registry in 1975 by Ellis et al 29 deseńbed the characteństics of the registry but eonfronted neither its relative meńt in eontńbuting to transfusion safety nor the question of geographic seope. A more reeent unpublished srudy of the use of the ARC donor deferral registry at six ARC regional blood eenters30 determined that, of 689,000 donations eolleeted over a 6-month peńod, there were 31 donations deteeted by the national eomponent of the registry that would not have been detected if only loeal eomponents were used. Of these, 17 disclosed abnormal testing. A simple extrapolation of this finding, aecounting for 12 million units eoIłeeted in the United States annually and all eolleetion agencies contńbuting to file, suggests that a nationwide deferral registry in the United States would prevent the distńbution of produets from approximately 600 donations that would not be deteeted by loeal registńes or be excluded by Other means, and would be distributed for transfusion. However, the fraction of these test-negative units that would earry transmissible virus, "window peńod" donations, is probably quite small. This study also used serological marker rates in an attempt to evaluate eaeh deferral eategory of the ARC donor file. These data suggested that, for a number of eategońes of the file, marker rates were not signifieant1y greater than the random or firsttime donor population. These were eategońes that ineorporated donors into the file by subjeetive health history information and not by previous testing results. Although there is little direct evidenee today that

donor deferral registńes have a major impaet on blood transfusion safety, as with other subjeetive methods we are likely to expeńenee their growth and inereased attention for the short term. They have beeome a main aetivity of blood eollection agencies and the FDA has focused attention on the manner in which they are used, even though there are no data to indicate they are useful. SUMMARY

In the last half of this century, donor deferral registńes have grown in size, scope, and importance for blood eollection organizations and regulatory agencies. This has oeeurred despite the laek of direct evidenee that, when used with all other methods, they eontribute meaningfully to the safety of the blood supply. Any deerease in the pereeived benefit of deferral registńes has been a result of the introduetion of a panoply of serological testing of donor blood intended to deteet transmissible disease. As the sensitivity of serological testing improves, the relative meńt of the subjeetive methods used for blood supply safety diminish. Although eomputers have beeome a mainstay in the management of deferral registńes, aceurate and eonsistent donor identification, good manual systems, and quality controi of data bases are key features to their sueeessful management. As with the other subjeetive methods used in maintaining blood supply safety, teehniques must be developed to determine the value of the many features of donor deferral registńes. Efforts must be made to simplify these processes and foeus on those elements that provide important eontńbu­ tions to blood supply safety. Today, donor deferral registńes are major aetivities in most blood eenters and are believed to play a significant role in blood supply safety. It is time for their role to be carefuIły reexamined.

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4. Menitove JE: The decreasing risk of transfusion-associated AIDS. N Engl J Med 321:966-968, 1989 5. Zuck TF, Sherwood WC, Bove JR: A review of recent events related to surrogate testing to prevent non-A, non-B post-transfusion hepatitis. Transfusion 27:203-206, 1987 6. Sugitani M, Inchauspe G, Shindo M: Sensitivity of serologic assays to identify blood donors with hepatitis C viraemia. Lancet 339:1018-1019, 1992 7. Silvergleid AJ. Leparc GF, Schmidt PJ: Impact of explicit

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questions about high-risk activities on donor attitudes and donor deferral patterns. Results in two community blood centers. Transfusion 29:362-364, 1989 8. Mayo DJ, Rose AM, Matchett SE, et al: Screening potential blood donors at risk for human immunodeficiency virus. Transfusion 31:466-474, 1991 9. Stramer SL, Heller JS, Coombs R, et al: Markers of HIV infection prior to IgO antibody seropositivity. JAMA 262:6469, 1989 10. Nelson KE, Donahue JO, Munoz A, et al: Transfusion of retroviruses from seronegative donors by transfusion during cardiac surgery. A multicenter study of HIV-I and HTLV-IlII infections. Ann Intern Med 117:612-614, 1992 11. Code of Federal Regulations, US Food and Drug Administration, vol 21, part 606.160 (e), 1991, P 37 12. Standards for Blood Banks and Transfusion Services (ed 14). American Association of Blood Banks, 1991 13. AuBuchon JP, Popovsky MA: The safety of preoperative blood donation in the nonhospital setting. Transfusion 31: 513-517, 1991 14. Kruskal MS: Controversies in transfusion medicine. The safety and utility of autologous donations by pregnant patients. Transfusion 30: 168-171, 1990 15. American Red Cross Blood Services Directive, no. 43.101. Donor Deferral Register, August 1992 16. Surgenor DM, Wallace EL, Hao SH, et al: Collection and transfusion of blood in the United States, 1982-1988. N Engl J Med 322:1646-51, 1990 17. Frenna D: Phonetic reduction of names. Comp Programs Biomed 19:31-36, 1984 18. Zuck T: Personal communication, October 1992 19. Kliman A: Australia antigen in volunteer and paid blood donors. N Engl J Med 284:109, 1971

WILLIAM C. SHERWOOD

20. Surgenor DM, Cerveny JF: A study of the conversion from paid to altruistic blood donors in New Mexico. Transfusion 18:54-63, 1978 21. Tabor E, Ooldfield M, Black HC, et al: Hepatitis B e antigen in volunteer and paid blood donors. Transfusion 20: 192-198, 1980 22. Miller WV: Paid blood donors. N Engl J Med 286:895, 1972 23. Petersen LR, Dodd RY, Dondero TJ: Methodologic approaches to surveillance of HIV infection among blood donors. Public Health Rep 105:153-157, 1990 24. Bastiaans MS, Nath N, Dodd RY, et al: Hepatitis associated markers in the American Red Cross volunteer blood donor population. IV. A comparison of HBV-associated serology markers in HBsAg-positive first time and repeat donors. Vox Sang 42:203-207, 1982 25. AuBuchon JP: Autologous transfusion and directed donations: Current controversies and future directions. Transfus Med Rev 3:290-306, 1989 26. Orindon AJ: Infectious disease markers in directed donors in the Atlanta region. Transfusion 31:872-873, 1991 27. Loiacono BR, Carter GR, Carter CS, et al: Efficacy of various methods of confidential unit exclusion in identifying potentially infectious blood donations. Transfusion 29:823826, 1989 28. Kean CA, Hsueh Y, Querin JJ, et al: A study of confi· dential unit exclusion. Transfusion 30:707-709, 1990 29. Ellis FR, Friedman LI, Wirak BF, et al: A computerized national Blood Donor Deferral Register. JAMA 19:722-724, 1975 30. Sherwood WC: Unpublished observations, August 1991