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ADVERSE OUTCOME OF PREGNANCY AND THE QUALITY OF OBSTETRIC CARE
Saturday 13 October
ADVERSE OUTCOME OF PREGNANCY AND THE QUALITY OF OBSTETRIC CARE KENNETH NISWANDER* GAYE HENSON IAIN CHALMERS DIANA ELBOURNE AIDAN MACFARLANE CHRISTOPHER REDMAN PETER TIZARD National Perinatal Epidemiology Unit, Radcliffe Infirmary, Oxford; and Nuffield Department of Obstetrics and Gynaecology and
Department of Paediatrics, University of Oxford The case-control method was used to study the relation between four possibly preventable adverse outcomes of pregnancy and suboptimal antepartum and intrapartum obstetric care defined by clinical consensus. Fetuses whose deaths were ascribed to asphyxia or trauma, and babies born at term who had seizures within 48 h of delivery, were significantly more likely than controls to have received suboptimal care during pregnancy. Babies with seizures, as well as those with terminal apnoea, were also substantially more likely than controls to have been born after a failure to react appropriately to signs of severe fetal distress during labour. Most of the babies who received suboptimal obstetric care, however, did not have any of these adverse outcomes. In addition, most babies with these adverse outcomes had apparently received satisfactory obstetric care. No relation was detected between cerebral palsy and suboptimal obstetric care.
Summary
Introduction OPINIONS continue to differ about the extent to which various adverse outcomes of pregnancy reflect preventable perinatal asphyxia. It is often assumed, for example, that the mothers of babies exhibiting signs attributed to "asphyxia" must have received obstetric care which was suboptimal. There are indeed specific clinical circumstances (for example, abruptio placentae and umbilical cord accidents) in which prompt obstetric intervention can reduce the likelihood of a baby being born asphyxiated. But neonatal depression can have causes other than asphyxia (for example, cerebral malformations) for which obstetric intervention has little to offer. 1-3 Hence it is not valid to assume that every baby born in poor condition has been asphyxiated during labour, or that he or she has received suboptimal obstetric care. In this paper we report our use of the case-control method to estimate the strength of the relation between each of four ’Present address: Department
of Obstetrics, University of California (Davis).
1984
clinical indicators of adverse outcome-fetal deaths ascribed asphyxia or trauma; terminal apnoea; very early neonatal seizures among babies born at term; and cerebral palsy-and suboptimal obstetric care defined by consensus. to
Materials and Methods Derivation and Definition
of Cases and Controls
The cases and controls compared in the present report were derived prospectively by the Oxford Cerebral Palsy Study4,S from 1’6 400 babies delivered at the John Radcliffe Hospital, Oxford, between Jan 1, 1978, and Dec 31, 1980. (Almost all the births to residents of South Oxfordshire occur at the hospital, but antenatal referral of some high-risk cases from outside the catchment area did occur during the period in question.) Resource constraints, rather than previous estimates of sample size, dictated that the recruitment phase should be limited to 3 years. The definition of both cases and controls in the Oxford Cerebral Palsy Study4differed from those used in the four specific case-control comparisons reported here because that study was designed with different objectives. A case series of 58 (3 -5per 1000 births) fetal deaths ascribed to asphyxia or trauma was available for study; 5 (0.3 3 per 1000 births) of these occurred during labour. In 53 (91-4%) of these 58 deaths, necropsy was performed before the deaths were ascribed to asphyxia or trauma; the remaining 5 deaths were assigned to this cause because there was no other obvious explanation. A consecutive series of 92 infants (5 -6per 1000 live births) during the 3-year recruitment phase had exhibited signs of terminal apnoea6 after delivery-that is, they became pink after resuscitation but before beginning to make spontaneous respiratory efforts. Over the same period, 36 infants (2 - 2 per 1000 live births) had had seizures within 4S h of birth at term.7 Two paediatricians, experienced in neurological examination of the newborn, scrutinised the clinical records of all babies reported to be neurologically abnormal at any stage to assess whether or not the documented evidence suggested that a seizure had occurred. A baby was deemed to have had a seizure if any of the following descriptions had been used by an experienced observer who had witnessed the abnormal physical signs: convulsion, fit, seizure, clonic movements, or jerky movements. Infants described only as jittery or tremulous were not included. A provisional diagnosis of cerebral palsy was made in a series of 34 eighteen-month-old children (2-1per 1000 live births). This caseseries was assembled in two ways by two paediatricians who applied the diagnostic criteria suggested by Lagergrento potential cases. Firstly, all survivors among the cases and controls entered into the Oxford Cerebral Palsy Study4,S were examined at home by a paediatrician who had no knowledge of the perinatal history; this prospective follow-up of neonates at high risk led to the identification of 22 of the 34 cases of cerebral palsy in the case series presented here. The remaining 12 cases were detected by case finding through various channels, in particular a detailed 8407 ©
828 examination of children who were not walking "five steps free" by the age of eighteen months. Again, the diagnosis in these children was made without knowledge of the details of the perinatal history. After a positive diagnosis, however, these details were collected and the fully documented cases were added to the study population assembled prospectively by the Oxford Cerebral Palsy Study. Four groups of random controls without the relevant condition of interest were derived from the totality of cases and controls assembled by the Oxford Cerebral Palsy Study. Each of these four groups of controls was then compared with the appropriate case series, as described above. Because individual liveborn infants were sometimes represented in more than one case series, and because the four case series varied in size, the number of controls available for comparison with each case series varied between 375 and 377. Although many of the control babies were used in all of the four groups of random controls, the differences in composition were sufficient to justify use of separate control groups for each of the four case series.
Reduction
of the Effect of Confounding Factors
Random as opposed to matched controls were chosen both because risk factors varied between the four case series and because of the limited size of the pool of fully documented potential controls assembled by the Oxford Cerebral Palsy Study. Instead, possible confounding was addressed by analyses in which adjustments were made for level of clinical complexity-a factor that we postulated would confound any association observed between the quality of obstetric care and adverse outcome. By reference to the clinical records, the complexity of each pregnancy and labour was assessed by an obstetrician (G. H.) using an agreed protocol (available on request). This assessment was made blind to the outcome of the pregnancy and led to the assignment of complexity scores for both pregnancy and labour independently. These scores reflected such factors as poor obstetric history, suspected intrauterine growth retardation, abnormalities of fetal heart rate, and preterm delivery. TABLE I-ESTIMATED RELATIVE,
Assessment of the
Quality of Obstetric Care
The following criteria for suboptimal obstetric care during pregnancy and in labour were derived from the clinical records of mothers delivered in 1981, and were subsequently endorsed by several experienced obstetricians:
Inappropriate response during pregnancy to social risk factors. -Failure to book before 20 weeks’ gestation and arrange visits every 4 weeks, or more frequently after 28 weeks: (i) in women who were unmarried and unsupported; (ii) in women who were less than 18 yr of age; (iii) in women in whom there was evidence of tobacco, alcohol, or other drug abuse. Inappropriate response during pregnancy to medical rzsk factors in the mother.-(i) Failure to order a plasma urea or creatinine in the presence of bacteriuria or a history of chronic renal disease; (ii) failure to perform fetal surveillance tests in the presence of severe hypertensive disease or diabetes mellitus.
Inappropriate response during pregnancy to fetal rzsk factors.-Failure to perform fetal surveillance with ultrasound and other tests of fetal well being in the presence of: (i) a reproductive history suggesting previous placental dysfunction; (ii) suspected intrauterine growth retardation; (iii) an elevated serum alpha-fetoprotein with a normal amniotic fluid alpha-fetoprotein; (iv) unexplained maternal weight loss; (v) a pregnancy duration of greater than 42 completed weeks. Inappropriate response to mdications for continuous fetal heart rate monztormg durzng labour.-Failure to use continuous electronic fetal heart rate monitoring during labour in the presence of: (i) severe hypertension; (11) diabetes mellitus; (iii) suspected intrauterine growth retardation; (iv) pregnancy duration of less than 36 or more than 42 completed weeks of gestation; (v) suspected abruptio placentae; (vi) meconium-stained amniotic fluid; (vii) administration of oxytocin or prostaglandins to induce or ’
accelerate labour. Inappropriate response to miscellaneous abnormalities during labour.(i) inadequate blood replacement for severe bleeding; (ii) failure to check for prolapse of the umbilical cord following rupture of the membranes; (ui) premeditated vaginal delivery of a footling breech. Inappropriate response to signs of severe intrapartum fetal distress. -Failure to respond promptly either by assessing fetal acid-base status by scalp blood sampling, or by effecting delivery, in the presence of: (i) prolonged
ATTRIBUTABLE, AND POPULATION ATTRIBUTABLE RISKS OF SUBOPTIMAL OBSTETRIC CARE IN CASES OF FETAL DEATH ASCRIBED TO ASPHYXIA OR TRAUMA
TABLE II-ESTIMATED
RELATIVE, ATTRIBUTABLE, AND POPULATION ATTRIBUTABLE RISKS OF SUBOPTIMAL OBSTETRIC CARE IN CASES OF TERMINAL APNOEA
829
bradycardia (within 40 min); (ii) severe variable decelerations (within 75 min); (lit) late decelerations (within 90 min). These criteria have not been validated scientifically but are intended reflect clinical consensus. For example, although it has not been demonstrated that use of continuous fetal heart rate monitoring when oxytocin is being administered lessens the risk of the adverse outcomes defined above, failure to use this form of fetal monitoring in these circumstances was nevertheless judged to be a departure from current standards of practice. These criteria were applied by one of us (K. R. N.) to the clinical records after an experienced midwife had obliterated from the records of both cases and controls all references to the condition of the infant at birth. When this "blind" assessment resulted in a judgment of suboptimal care, the records were reviewed by a second obstetrician (G. H.), again "blind" to the condition of the infant at birth. The second obstetrician also reviewed a 1-in-5 sample of those cases in which care was judged to have met acceptable standards. In no case was frank disagreement between the assessors encountered, probably because the criteria were so explicit. In 3 cases where a judgment was particularly difficult, the cases were reviewed by the two obstetricians in conference, and a decision satisfactory to both obstetricians was easily reached. to
formally
Statistical Methods When all the judgments had been made and recorded, the identity of the cases and controls was revealed and tabulations were prepared comparing the frequency of suboptimal obstetric care in cases and controls. Relative risks were derived from the odds-ratioand given approximate confidence intervals as suggested by Woolf. 10 Where appropriate, Fisher’s exact testll was used to test whether the relative risk differed significantly from unity. Attributable risks and their approximate confidence intervals were estimated by the methods described by Miettinen.12 Population attributable risks were estimated by the methods described by Levin,13 and Walter’s approximate confidence intervalsl4 were calculated for each of these
-
estimates. Where the approximate confidence intervals for the three types of risk appear inconsistent, those of the relative risks are the most accurate. Summary relative risks taking into account confounding by clinical complexity were calculated by the MantelHaenszel method. 15,16
Results The frequencies of suboptimal care during pregnancy and labour in cases and controls were compared and relative risks, attributable risks and population attributable risks estimated. Tables I-IV present these data for fetal deaths, terminal apnoea, very early neonatal seizures, and cerebral palsy. Despite the small numbers of cases studied, some of the estimated relative risks are unlikely to have occurred by chance. Fetuses whose deaths were ascribed to asphyxia or trauma and infants born at term who had seizures within 48 h of delivery were significantly more likely than controls to have received suboptimal care during pregnancy. The babies with seizures and those with terminal apnoea were also substantially more likely than controls to have been born after a failure to react appropriately to signs of severe fetal distress during labour. By contrast, no relation was detected between suboptimal obstetric care and a diagnosis of cerebral palsy at eighteen months of age. All but one of these crude estimates of relative risk were reduced when clinical complexity was taken into account, suggesting that this was, as anticipated, a confounding factor in the associations observed. In only two comparisons, however, were the crude estimates of relative risk altered substantially. For cases of fetal death and neonatal seizures the relative risk ofsuboptimal care during pregnancy -fell, from 3’ 7 and 3’ 4, to 3 - 3 and 2 - 5, respectively. The attributable risks presented are estimates of the numbers of each adverse outcome which would be likely to be
TABLE III-ESTIMATED RELATIVE, ATTRIBUTABLE, AND POPULATION ATTRIBUTABLE RISKS OF SUBOPTIMAL OBSTETRIC CARE IN CASES OF VERY EARLY NEONATAL SEIZURES IN BABIES BORN AT TERM I
TABLE IV-ESTIMATED
RELATIVE, ATTRIBUTABLE,
I
I
I
I
I
AND POPULATION RISKS OF SUBOPTIMAL OBSTETRIC CARE IN CASES OF CEREBRAL PALSY i
830
caused by 1000 instances of suboptimal care. It is clear from these estimates that most of the babies whose mothers have received suboptimal care as defined in the study will escape developing terminal apnoea, neonatal seizures, or cerebral
palsy. The population attributable risks are estimates of the proportions of cases of each adverse outcome that might be attributed to suboptimal obstetric care. Again it is clear that
of the cases of adverse outcome examined could not be attributed to suboptimal care as defined in this study. The population attributable risks range from estimates which suggest, at one extreme, that suboptimal care in labour may account for one in three fetal deaths ascribed to intrapartum asphyxia, to estimates which suggest, perversely, that suboptimal obstetric care may actually be negatively associated with cerebral palsy. most
Discussion asserted that certain adverse reflect "suboptimal" obstetric care, pregnancy has not until now been systematically care suboptimal defined, nor related quantitatively to poor perinatal outcome. We believe that this is the first study in which an attempt has been made to analyse these matters objectively. The results must be considered in the light of our methods and sample sizes. Ideally, different forms of care should be compared in a prospective, randomised experiment because this is the most certain way of controlling for selection biases which confound analyses of observational data. However, a randomised trial cannot be used to compare "suboptimal" with "acceptable" obstetric care as defined by consensus. It may sometimes be possible to exploit natural experiments by comparing the frequencies of adverse outcomes of pregnancy in complete but geographically distinct populations receiving obstetric care of contrasting quality. For example, Bakketeig and his colleagues!7 studied the relation between the level of staffing and facilities (a less sensitive matter than the quality of care) and birthweightspecific mortality rates in Norwegian counties. Alternatively, cohorts within a single total obstetric population might be defined by whether or not they had received suboptimal care and then the incidence of adverse outcome compared. The data from the present study suggest that in a cohort of 1000 subjects receiving suboptimal care during pregnancy (at a prevalence of 4’ 6%), only 4 deaths would be expected, 1 of which would have been caused by factors other than suboptimal care. To have an 80% chance of detecting the consequences of suboptimal obstetric care of this magnitude on fetal deaths ascribed to asphyxia or trauma, it would be necessary to study a cohort of at least 2000 women experiencing suboptimal care. The case notes of 43 500 maternities would have to be studied (by an investigator blind to the outcome) to identify a cohort of this size. In the light of these and earlier considerations we have preferred the casecontrol method, whilst recognising its limitations.!8,!9 Use of this study design is certainly preferable to the common practice in both clinical and legal settings of imputing relations between adverse perinatal outcome and suboptimal obstetric care from uncontrolled observations based on single
Although
it is
frequently
outcomes
.
cases or case
series.
Our estimates of crude relative risks are reduced when the clinical complexity of cases and controls is taken into account. This may reflect an increased likelihood of lapses in care in circumstances in which a greater number of important clinical decisions have to be made. But clinical complexity only proved to be an important confounding variable in the
association between suboptimal obstetric care before labour and fetal death and neonatal seizures. We have estimated that only 4% of cases of terminal apnoea could be attributed to even severe lapses of intrapartum care (table III). A somewhat larger proportion of cases of neonatal seizures could be attributed to suboptimal intrapartum care; this finding is consistent with the results of a recently completed randomised trial in which the incidence of convulsions was halved by more intensive intrapartum fetal monitoring.20 It was really only among fetal deaths, however, that an appreciable proportion of cases (30%) could be attributed to suboptimal intrapartum care. Even for these deaths, the upper limits of the 95% confidence intervals indicate that it is very unlikely that all such deaths could be abolished by avoiding the type of intrapartum care described as suboptimal in this study. Furthermore, our estimates of attributable risk would indicate that, in 1000 instances of suboptimal intrapartum care, only 3 babies would be expected to die as a result of such care. The finding in this study that cerebral palsy, as diagnosed at eighteen months of age, was not associated with suboptimal obstetric care is consistent with other evidence suggesting that cerebral palsy is only very rarely preceded by potentially preventable perinatal asphyxia.21,22 Case definition and classification may alter as the children become older,23 but this is unlikely to change the overall picture which has
emerged. It is possible
that larger relative and attributable risks would have been obtained either by using different criteria for judging care to have been suboptimal (for example, potentially traumatic instrumental delivery), or by selecting different outcome indicators, such as neonatal acidosis or only the dyskinetic forms of cerebral palsy. Our findings might also have been different had we used larger sample sizes or other methods to control for confounding factors. Failure to achieve adequate control of confounding factors in the present study, for example, may have led us to overestimate some of the risks associated with suboptimal care. In future studies we shall try to match cases and controls more closely by the clinical problems for which the quality of care is to be assessed. Certainly there is great scope for developing and extending the approach we have used. Meanwhile we believe that our results have three important practical implications. Firstly, our data confirm that the frequencies of both fetal deaths ascribed to asphyxia and trauma and very early neonatal seizures in babies born at term are valid indicators of the quality of obstetric care. Secondly, our data confirm how important it is to ensure that signs of severe intrapartum fetal distress are acted upon promptly. Lastly, it is clear that individual cases of cerebral palsy and other forms of adverse pregnancy outcome are in most cases unlikely to have been caused by suboptimal obstetric care as defined in this study. We wish to acknowledge our indebtedness to those who made this study the consultant staff of the John Radcliffe Maternity Unit who allowed their practice to be assessed; Jennifer Dennis and Lesley Mutch for defining the seizure cases; Rosemary King and Ruth Niswander for preparing the material for analysis; Wendy Thompson for help with analysing the case notes; Peter Smith and Paul Stolley for methodological advice; Jim Hetherington and Lesley Mierh for typing the scripts; the many colleagues who have helped us by commenting on earlier drafts; the Leverhulme Trust which supported the Oxford Cerebral Palsy Study with a grant made through the Royal College of Physicians; and the Department of Health and Social Security which provided salary support for D. E. and 1. C.
possible:
Correspondence should be addressed to 1. C., National Epidemiology Unit, Radcliffe Infirmary, Oxford OX2 6HE.
Perinatal
831
ORAL "HAIRY" LEUCOPLAKIA IN MALE OF ASSOCIATION WITH BOTH PAPILLOMAVIRUS AND A HERPES-GROUP VIRUS
HOMOSEXUALS: EVIDENCE
DEBORAH GREENSPAN MARCUS CONANT SOL SILVERMAN, JR
JOHN S. GREENSPAN VIBEKE PETERSEN YVONNE DE SOUZA
Departments of Stomatology (Divisions of Oral Medicine and Oral Biology), Dermatology, and Pathology, Schools of Dentistry and Medicine, University of California, San Francisco, California, USA An outbreak of a new form of oral leucoplakia, found principally on the lateral borders of the tongue, is reported in male homosexuals in the San Francisco area. Many of the patients showed evidence of immunosuppression, and candida was often found in the lesions. The characteristic histology is similar to that of the flat wart of skin. There was immunocytochemical evidence of papillomavirus core antigen in 77% of 30 biopsy specimens, but no papillomaviruses were detected by electron microscopy in samples from 6 randomly selected patients. In 5 of these 6 patients there was evidence of a herpes-type virus. Pneumocystis carinii pneumonia has developed in 8 of 37 patients in a 33-month period. This leucoplakia may presage AIDS, may be associated with both papillomavirus and a herpes-type virus, and may offer clues to the pathogenesis of other forms of oral epithelial hyperplasia and dysplasia.
Summary
Introduction
epidemic of acquired immunodeficiency syndrome (AIDS), consisting of Kaposi’s sarcoma and Pneumocystis carinii pneumonia or other life-threatening opportunistic infections, became apparent in young male homosexuals in San Francisco. At that time we began to see LATE in 1981 the
otherwise healthy men with unusual white lesions of the tongue (hairy leucoplakia, HL). Having first taken it to be candidiasis, we now believe that this condition is a separate entity not previously described in the mouth. We here present preliminary clinical, histopathological, and virological observations in 37 patients with HL followed for up to 33 months. ,
Patients and Methods Patients.-The patients were referred to the oral medicine clinic at the University of California, San Francisco, from the UCSF AIDS Clinical Research Center or by physicians and dentists in the 1.
Gross H, Jellinger K, Kaltenback E, Rett A. Infantile cerebral disorders: clinicalneuropathological correlations to elucidate the aetiological factors. J Neurol Sci
1968; 7: 551-64. 2 Illingworth RS. 3 Chiswick ML,
Why blame the obstetrician? Br Med J 1979; i: 797-801. D’Souza SW, Occleshaw JV. Computerized transverse axial tomography in the newborn. Early Hum Devel 1977; 1: 171-80. 4. Macfarlane JA. Studies in Cerebral Palsy. In: Chalmers I, McIlwaine G, eds. Perinatal audit and surveillance London: Royal College of Obstetricians and Gynaecologists, 1980: 173-87. JA, Redman CWG, Hardie J. The Oxford Cerebral Palsy Study-1978 Results. Devel Med Child Neural 1981; 23: 112. 6 Gupta JM, Tizard JPM. The sequence of events in neonatal apnoea. Lancet 1967; ii: 55-59 7 Dennis J, Chalmers I. Very early neonatal seizure rate: a possible epidemiological indicator of the quality of perinatal care Br J Obstet Gynaecol 1982, 89: 418-26. 8. Lagergren J. Children with motor handicaps. Acta Paediatr Scand 1981; suppl 289. 9 Cornfield J A method of estimating comparative rates from clinical data Application to cancer of the lung, breast and cervix. J Natl Cancer Inst 1951; 11: 1269-75. 10 Woolf B. On estimating the relation between blood group and disease. Ann Hum Genet 1955; 19: 251-53. 11. Fisher RA. The logic of inductive inference. J Roy Stat Soc A 1953; 98: 39-54. 12. Miettinen OS. Estimability and estimation in case-referent studies. Am J Epidemiol 1976; 103: 226-35. 13 Levin ML. The occurrence of lung cancer in man. Acta Un Int Contra Cancrum 1953; 9: 531-41. 5 Macfarlane
city of San Francisco. All patients gave a detailed medical and social history in response to standard questionnaires and had complete physical and oral examinations. When oral white lesions were found, smear and culture for candida were performed. Oral biopsy.-35 biopsy specimens were obtained from 30 patients under local anaesthesia. Routine histopathology and periodicacid/Schiff (PAS) staining was performed on formol-saline-fixed, paraffin-embedded samples. Samples from 6 cases selected at random were also obtained for electron microscopy; these were fixed with 3% glutaraldehydel followed by postfixing in 1% buffered osmic acid2and epon-embedding.3 The sections were stained with lead citrate.4 Immunological studies.-Delayed cutaneous hypersensitivity to purified protein derivative (PPD), candida, mumps, and trichophytin antigens was tested. Phenotypic characterisation and measurement of OKT4 (helper T cells) and OKT8 (suppressor cytotoxic T cells) (Ortho Pharmaceutical, Raritan, New Jersey) of peripheral blood lymphocytes was kindly performed by Dr Conrad Casavant, Department of Laboratory Medicine, UCSF. Papillomavirus antigen.-Evidence for the presence of papillomavirus antigen within the lesion was sought in paraffin-embedded sections by means of a peroxidase-antiperoxidase (PAP) technique with an antiserum to the core antigen of the papillomavirus group. The antiserum was raised in rabbits and the method used, briefly, was as follows: sections were deparaffinised, rehydrated, and washed in 0 - 5 mol/l "tris" buffer (pH 7 - 6). To quench endogenous peroxidase, sections were incubated in 3% hydrogen peroxide for 5 min; next came a 20 min incubation in 20% normal swine serum to reduce nonspecific staining. The sections were then incubated overnight in rabbit antiserum to bovine papillomavirus type 1 (Dako, Santa Barbara, California, PAP Kit TMK521) diluted 1:5000 with "tris" buffer. Control sections were treated in the same manner with the serum of non-immunised rabbits. The secondary antiserum was swine anti-rabbit immunoglobulin diluted 1:100 and placed on the section for 20 min. This was followed by a 20-min incubation with rabbit PAP complex diluted 1:100. The final reaction product was obtained by the use of a substrate solution of 0-3% hydrogen peroxide and 0-02% aminoethylcarbazole (AEC) placed on sections for 40 min. The AEC is oxidised by peroxide to form a red precipitate at the reaction site, thus localising the papillomavirus antigen. The sections were then counterstained in Mayer’s haematoxylin, rinsed, and mounted in glycerol gelatin. All washings between incubations were performed with 0-55 mol/1 "tris" buffer (pH 7 - 6). Control tissues were 7 oral warts (positive control) and 10 specimens of other oral mucosal lesions (4 of epithelial hyperplasia, 4 of candidiasis, and 2 of fibroepithelial hyperplasia) obtained from the files of the oral pathology service, UCSF.
Results
Clinica/.-Between October, 1981, and July, 1984, 37 homosexual men presented with white lesions of the tongue; 14. Walter SD. The distribution of Levin’s measure of attributable risk Biometrika 1975; 62: 371-74. 15. Mantel N, Haenszel W. Statistical aspects of the analysis of data from retrospective studies of disease. J Natl Cancer Inst 1959; 22: 719-48 16. Mantel N. Chi-square tests with one degree of freedom. Extensions of the MantelHaenszel Procedure. J Am Stat Assoc 1963; 58: 690-700. 17. Bakketeig LS, Hoffman HJ, Sternthal PM. Obstetric service and perinatal mortality in Norway. Acta Obstet Gynaecol Scand 1978; 77: 3-19 suppl. 18. Sackett DL. Bias in analytic research. J Chron Dis 1979; 32: 51-63. 19. Alberman E, Stanley F. Guidelines to the Epidemiological Approach. In: Stanley F, Alberman E, eds The epidemiology of the cerebral palsies, (Clin Devel Med no 87). London: Spastics International Medical Publications/Blackwell Scientific Publications, 1984: 172-83. 20. Macdonald D, Grant AM, Pereira M, Boylan P, Chalmers I. The Dublin randomised controlled trial of intrapartum electronic fetal heart rate monitoring. Paper presented at 23rd British Congress of Obstetrics and Gynaecology, Birmingham,
July 13, 1983. N, Stark RI. Cerebral palsy and mental retardation in relation to indicators of perinatal asphyxia. Am J Obstet Gynecol 1983; 147: 960-66. Nelson KB, Ellenberg JH. Obstetric complications as risk factors for cerebral palsy or seizure disorders. JAMA 1984; 251: 1843-48. Stanley FJ Using cerebral palsy data in the evaluation of neonatal intensive care: a warning. Devel Med Child Neurol 1982; 24: 93-94.
21. Paneth 22. 23.
ADVERSE OUTCOME OF PREGNANCY AND THE QUALITY OF OBSTETRIC CARE KENNETH NISWANDER* GAYE HENSON IAIN CHALMERS DIANA ELBOURNE AIDAN MACFARLANE CHRISTOPHER REDMAN PETER TIZARD National Perinatal Epidemiology Unit, Radcliffe Infirmary, Oxford; and Nuffield Department of Obstetrics and Gynaecology and
Department of Paediatrics, University of Oxford The case-control method was used to study the relation between four possibly preventable adverse outcomes of pregnancy and suboptimal antepartum and intrapartum obstetric care defined by clinical consensus. Fetuses whose deaths were ascribed to asphyxia or trauma, and babies born at term who had seizures within 48 h of delivery, were significantly more likely than controls to have received suboptimal care during pregnancy. Babies with seizures, as well as those with terminal apnoea, were also substantially more likely than controls to have been born after a failure to react appropriately to signs of severe fetal distress during labour. Most of the babies who received suboptimal obstetric care, however, did not have any of these adverse outcomes. In addition, most babies with these adverse outcomes had apparently received satisfactory obstetric care. No relation was detected between cerebral palsy and suboptimal obstetric care.
Summary
Introduction OPINIONS continue to differ about the extent to which various adverse outcomes of pregnancy reflect preventable perinatal asphyxia. It is often assumed, for example, that the mothers of babies exhibiting signs attributed to "asphyxia" must have received obstetric care which was suboptimal. There are indeed specific clinical circumstances (for example, abruptio placentae and umbilical cord accidents) in which prompt obstetric intervention can reduce the likelihood of a baby being born asphyxiated. But neonatal depression can have causes other than asphyxia (for example, cerebral malformations) for which obstetric intervention has little to offer. 1-3 Hence it is not valid to assume that every baby born in poor condition has been asphyxiated during labour, or that he or she has received suboptimal obstetric care. In this paper we report our use of the case-control method to estimate the strength of the relation between each of four ’Present address: Department
of Obstetrics, University of California (Davis).
1984
clinical indicators of adverse outcome-fetal deaths ascribed asphyxia or trauma; terminal apnoea; very early neonatal seizures among babies born at term; and cerebral palsy-and suboptimal obstetric care defined by consensus. to
Materials and Methods Derivation and Definition
of Cases and Controls
The cases and controls compared in the present report were derived prospectively by the Oxford Cerebral Palsy Study4,S from 1’6 400 babies delivered at the John Radcliffe Hospital, Oxford, between Jan 1, 1978, and Dec 31, 1980. (Almost all the births to residents of South Oxfordshire occur at the hospital, but antenatal referral of some high-risk cases from outside the catchment area did occur during the period in question.) Resource constraints, rather than previous estimates of sample size, dictated that the recruitment phase should be limited to 3 years. The definition of both cases and controls in the Oxford Cerebral Palsy Study4differed from those used in the four specific case-control comparisons reported here because that study was designed with different objectives. A case series of 58 (3 -5per 1000 births) fetal deaths ascribed to asphyxia or trauma was available for study; 5 (0.3 3 per 1000 births) of these occurred during labour. In 53 (91-4%) of these 58 deaths, necropsy was performed before the deaths were ascribed to asphyxia or trauma; the remaining 5 deaths were assigned to this cause because there was no other obvious explanation. A consecutive series of 92 infants (5 -6per 1000 live births) during the 3-year recruitment phase had exhibited signs of terminal apnoea6 after delivery-that is, they became pink after resuscitation but before beginning to make spontaneous respiratory efforts. Over the same period, 36 infants (2 - 2 per 1000 live births) had had seizures within 4S h of birth at term.7 Two paediatricians, experienced in neurological examination of the newborn, scrutinised the clinical records of all babies reported to be neurologically abnormal at any stage to assess whether or not the documented evidence suggested that a seizure had occurred. A baby was deemed to have had a seizure if any of the following descriptions had been used by an experienced observer who had witnessed the abnormal physical signs: convulsion, fit, seizure, clonic movements, or jerky movements. Infants described only as jittery or tremulous were not included. A provisional diagnosis of cerebral palsy was made in a series of 34 eighteen-month-old children (2-1per 1000 live births). This caseseries was assembled in two ways by two paediatricians who applied the diagnostic criteria suggested by Lagergrento potential cases. Firstly, all survivors among the cases and controls entered into the Oxford Cerebral Palsy Study4,S were examined at home by a paediatrician who had no knowledge of the perinatal history; this prospective follow-up of neonates at high risk led to the identification of 22 of the 34 cases of cerebral palsy in the case series presented here. The remaining 12 cases were detected by case finding through various channels, in particular a detailed 8407 ©
828 examination of children who were not walking "five steps free" by the age of eighteen months. Again, the diagnosis in these children was made without knowledge of the details of the perinatal history. After a positive diagnosis, however, these details were collected and the fully documented cases were added to the study population assembled prospectively by the Oxford Cerebral Palsy Study. Four groups of random controls without the relevant condition of interest were derived from the totality of cases and controls assembled by the Oxford Cerebral Palsy Study. Each of these four groups of controls was then compared with the appropriate case series, as described above. Because individual liveborn infants were sometimes represented in more than one case series, and because the four case series varied in size, the number of controls available for comparison with each case series varied between 375 and 377. Although many of the control babies were used in all of the four groups of random controls, the differences in composition were sufficient to justify use of separate control groups for each of the four case series.
Reduction
of the Effect of Confounding Factors
Random as opposed to matched controls were chosen both because risk factors varied between the four case series and because of the limited size of the pool of fully documented potential controls assembled by the Oxford Cerebral Palsy Study. Instead, possible confounding was addressed by analyses in which adjustments were made for level of clinical complexity-a factor that we postulated would confound any association observed between the quality of obstetric care and adverse outcome. By reference to the clinical records, the complexity of each pregnancy and labour was assessed by an obstetrician (G. H.) using an agreed protocol (available on request). This assessment was made blind to the outcome of the pregnancy and led to the assignment of complexity scores for both pregnancy and labour independently. These scores reflected such factors as poor obstetric history, suspected intrauterine growth retardation, abnormalities of fetal heart rate, and preterm delivery. TABLE I-ESTIMATED RELATIVE,
Assessment of the
Quality of Obstetric Care
The following criteria for suboptimal obstetric care during pregnancy and in labour were derived from the clinical records of mothers delivered in 1981, and were subsequently endorsed by several experienced obstetricians:
Inappropriate response during pregnancy to social risk factors. -Failure to book before 20 weeks’ gestation and arrange visits every 4 weeks, or more frequently after 28 weeks: (i) in women who were unmarried and unsupported; (ii) in women who were less than 18 yr of age; (iii) in women in whom there was evidence of tobacco, alcohol, or other drug abuse. Inappropriate response during pregnancy to medical rzsk factors in the mother.-(i) Failure to order a plasma urea or creatinine in the presence of bacteriuria or a history of chronic renal disease; (ii) failure to perform fetal surveillance tests in the presence of severe hypertensive disease or diabetes mellitus.
Inappropriate response during pregnancy to fetal rzsk factors.-Failure to perform fetal surveillance with ultrasound and other tests of fetal well being in the presence of: (i) a reproductive history suggesting previous placental dysfunction; (ii) suspected intrauterine growth retardation; (iii) an elevated serum alpha-fetoprotein with a normal amniotic fluid alpha-fetoprotein; (iv) unexplained maternal weight loss; (v) a pregnancy duration of greater than 42 completed weeks. Inappropriate response to mdications for continuous fetal heart rate monztormg durzng labour.-Failure to use continuous electronic fetal heart rate monitoring during labour in the presence of: (i) severe hypertension; (11) diabetes mellitus; (iii) suspected intrauterine growth retardation; (iv) pregnancy duration of less than 36 or more than 42 completed weeks of gestation; (v) suspected abruptio placentae; (vi) meconium-stained amniotic fluid; (vii) administration of oxytocin or prostaglandins to induce or ’
accelerate labour. Inappropriate response to miscellaneous abnormalities during labour.(i) inadequate blood replacement for severe bleeding; (ii) failure to check for prolapse of the umbilical cord following rupture of the membranes; (ui) premeditated vaginal delivery of a footling breech. Inappropriate response to signs of severe intrapartum fetal distress. -Failure to respond promptly either by assessing fetal acid-base status by scalp blood sampling, or by effecting delivery, in the presence of: (i) prolonged
ATTRIBUTABLE, AND POPULATION ATTRIBUTABLE RISKS OF SUBOPTIMAL OBSTETRIC CARE IN CASES OF FETAL DEATH ASCRIBED TO ASPHYXIA OR TRAUMA
TABLE II-ESTIMATED
RELATIVE, ATTRIBUTABLE, AND POPULATION ATTRIBUTABLE RISKS OF SUBOPTIMAL OBSTETRIC CARE IN CASES OF TERMINAL APNOEA
829
bradycardia (within 40 min); (ii) severe variable decelerations (within 75 min); (lit) late decelerations (within 90 min). These criteria have not been validated scientifically but are intended reflect clinical consensus. For example, although it has not been demonstrated that use of continuous fetal heart rate monitoring when oxytocin is being administered lessens the risk of the adverse outcomes defined above, failure to use this form of fetal monitoring in these circumstances was nevertheless judged to be a departure from current standards of practice. These criteria were applied by one of us (K. R. N.) to the clinical records after an experienced midwife had obliterated from the records of both cases and controls all references to the condition of the infant at birth. When this "blind" assessment resulted in a judgment of suboptimal care, the records were reviewed by a second obstetrician (G. H.), again "blind" to the condition of the infant at birth. The second obstetrician also reviewed a 1-in-5 sample of those cases in which care was judged to have met acceptable standards. In no case was frank disagreement between the assessors encountered, probably because the criteria were so explicit. In 3 cases where a judgment was particularly difficult, the cases were reviewed by the two obstetricians in conference, and a decision satisfactory to both obstetricians was easily reached. to
formally
Statistical Methods When all the judgments had been made and recorded, the identity of the cases and controls was revealed and tabulations were prepared comparing the frequency of suboptimal obstetric care in cases and controls. Relative risks were derived from the odds-ratioand given approximate confidence intervals as suggested by Woolf. 10 Where appropriate, Fisher’s exact testll was used to test whether the relative risk differed significantly from unity. Attributable risks and their approximate confidence intervals were estimated by the methods described by Miettinen.12 Population attributable risks were estimated by the methods described by Levin,13 and Walter’s approximate confidence intervalsl4 were calculated for each of these
-
estimates. Where the approximate confidence intervals for the three types of risk appear inconsistent, those of the relative risks are the most accurate. Summary relative risks taking into account confounding by clinical complexity were calculated by the MantelHaenszel method. 15,16
Results The frequencies of suboptimal care during pregnancy and labour in cases and controls were compared and relative risks, attributable risks and population attributable risks estimated. Tables I-IV present these data for fetal deaths, terminal apnoea, very early neonatal seizures, and cerebral palsy. Despite the small numbers of cases studied, some of the estimated relative risks are unlikely to have occurred by chance. Fetuses whose deaths were ascribed to asphyxia or trauma and infants born at term who had seizures within 48 h of delivery were significantly more likely than controls to have received suboptimal care during pregnancy. The babies with seizures and those with terminal apnoea were also substantially more likely than controls to have been born after a failure to react appropriately to signs of severe fetal distress during labour. By contrast, no relation was detected between suboptimal obstetric care and a diagnosis of cerebral palsy at eighteen months of age. All but one of these crude estimates of relative risk were reduced when clinical complexity was taken into account, suggesting that this was, as anticipated, a confounding factor in the associations observed. In only two comparisons, however, were the crude estimates of relative risk altered substantially. For cases of fetal death and neonatal seizures the relative risk ofsuboptimal care during pregnancy -fell, from 3’ 7 and 3’ 4, to 3 - 3 and 2 - 5, respectively. The attributable risks presented are estimates of the numbers of each adverse outcome which would be likely to be
TABLE III-ESTIMATED RELATIVE, ATTRIBUTABLE, AND POPULATION ATTRIBUTABLE RISKS OF SUBOPTIMAL OBSTETRIC CARE IN CASES OF VERY EARLY NEONATAL SEIZURES IN BABIES BORN AT TERM I
TABLE IV-ESTIMATED
RELATIVE, ATTRIBUTABLE,
I
I
I
I
I
AND POPULATION RISKS OF SUBOPTIMAL OBSTETRIC CARE IN CASES OF CEREBRAL PALSY i
830
caused by 1000 instances of suboptimal care. It is clear from these estimates that most of the babies whose mothers have received suboptimal care as defined in the study will escape developing terminal apnoea, neonatal seizures, or cerebral
palsy. The population attributable risks are estimates of the proportions of cases of each adverse outcome that might be attributed to suboptimal obstetric care. Again it is clear that
of the cases of adverse outcome examined could not be attributed to suboptimal care as defined in this study. The population attributable risks range from estimates which suggest, at one extreme, that suboptimal care in labour may account for one in three fetal deaths ascribed to intrapartum asphyxia, to estimates which suggest, perversely, that suboptimal obstetric care may actually be negatively associated with cerebral palsy. most
Discussion asserted that certain adverse reflect "suboptimal" obstetric care, pregnancy has not until now been systematically care suboptimal defined, nor related quantitatively to poor perinatal outcome. We believe that this is the first study in which an attempt has been made to analyse these matters objectively. The results must be considered in the light of our methods and sample sizes. Ideally, different forms of care should be compared in a prospective, randomised experiment because this is the most certain way of controlling for selection biases which confound analyses of observational data. However, a randomised trial cannot be used to compare "suboptimal" with "acceptable" obstetric care as defined by consensus. It may sometimes be possible to exploit natural experiments by comparing the frequencies of adverse outcomes of pregnancy in complete but geographically distinct populations receiving obstetric care of contrasting quality. For example, Bakketeig and his colleagues!7 studied the relation between the level of staffing and facilities (a less sensitive matter than the quality of care) and birthweightspecific mortality rates in Norwegian counties. Alternatively, cohorts within a single total obstetric population might be defined by whether or not they had received suboptimal care and then the incidence of adverse outcome compared. The data from the present study suggest that in a cohort of 1000 subjects receiving suboptimal care during pregnancy (at a prevalence of 4’ 6%), only 4 deaths would be expected, 1 of which would have been caused by factors other than suboptimal care. To have an 80% chance of detecting the consequences of suboptimal obstetric care of this magnitude on fetal deaths ascribed to asphyxia or trauma, it would be necessary to study a cohort of at least 2000 women experiencing suboptimal care. The case notes of 43 500 maternities would have to be studied (by an investigator blind to the outcome) to identify a cohort of this size. In the light of these and earlier considerations we have preferred the casecontrol method, whilst recognising its limitations.!8,!9 Use of this study design is certainly preferable to the common practice in both clinical and legal settings of imputing relations between adverse perinatal outcome and suboptimal obstetric care from uncontrolled observations based on single
Although
it is
frequently
outcomes
.
cases or case
series.
Our estimates of crude relative risks are reduced when the clinical complexity of cases and controls is taken into account. This may reflect an increased likelihood of lapses in care in circumstances in which a greater number of important clinical decisions have to be made. But clinical complexity only proved to be an important confounding variable in the
association between suboptimal obstetric care before labour and fetal death and neonatal seizures. We have estimated that only 4% of cases of terminal apnoea could be attributed to even severe lapses of intrapartum care (table III). A somewhat larger proportion of cases of neonatal seizures could be attributed to suboptimal intrapartum care; this finding is consistent with the results of a recently completed randomised trial in which the incidence of convulsions was halved by more intensive intrapartum fetal monitoring.20 It was really only among fetal deaths, however, that an appreciable proportion of cases (30%) could be attributed to suboptimal intrapartum care. Even for these deaths, the upper limits of the 95% confidence intervals indicate that it is very unlikely that all such deaths could be abolished by avoiding the type of intrapartum care described as suboptimal in this study. Furthermore, our estimates of attributable risk would indicate that, in 1000 instances of suboptimal intrapartum care, only 3 babies would be expected to die as a result of such care. The finding in this study that cerebral palsy, as diagnosed at eighteen months of age, was not associated with suboptimal obstetric care is consistent with other evidence suggesting that cerebral palsy is only very rarely preceded by potentially preventable perinatal asphyxia.21,22 Case definition and classification may alter as the children become older,23 but this is unlikely to change the overall picture which has
emerged. It is possible
that larger relative and attributable risks would have been obtained either by using different criteria for judging care to have been suboptimal (for example, potentially traumatic instrumental delivery), or by selecting different outcome indicators, such as neonatal acidosis or only the dyskinetic forms of cerebral palsy. Our findings might also have been different had we used larger sample sizes or other methods to control for confounding factors. Failure to achieve adequate control of confounding factors in the present study, for example, may have led us to overestimate some of the risks associated with suboptimal care. In future studies we shall try to match cases and controls more closely by the clinical problems for which the quality of care is to be assessed. Certainly there is great scope for developing and extending the approach we have used. Meanwhile we believe that our results have three important practical implications. Firstly, our data confirm that the frequencies of both fetal deaths ascribed to asphyxia and trauma and very early neonatal seizures in babies born at term are valid indicators of the quality of obstetric care. Secondly, our data confirm how important it is to ensure that signs of severe intrapartum fetal distress are acted upon promptly. Lastly, it is clear that individual cases of cerebral palsy and other forms of adverse pregnancy outcome are in most cases unlikely to have been caused by suboptimal obstetric care as defined in this study. We wish to acknowledge our indebtedness to those who made this study the consultant staff of the John Radcliffe Maternity Unit who allowed their practice to be assessed; Jennifer Dennis and Lesley Mutch for defining the seizure cases; Rosemary King and Ruth Niswander for preparing the material for analysis; Wendy Thompson for help with analysing the case notes; Peter Smith and Paul Stolley for methodological advice; Jim Hetherington and Lesley Mierh for typing the scripts; the many colleagues who have helped us by commenting on earlier drafts; the Leverhulme Trust which supported the Oxford Cerebral Palsy Study with a grant made through the Royal College of Physicians; and the Department of Health and Social Security which provided salary support for D. E. and 1. C.
possible:
Correspondence should be addressed to 1. C., National Epidemiology Unit, Radcliffe Infirmary, Oxford OX2 6HE.
Perinatal
831
ORAL "HAIRY" LEUCOPLAKIA IN MALE OF ASSOCIATION WITH BOTH PAPILLOMAVIRUS AND A HERPES-GROUP VIRUS
HOMOSEXUALS: EVIDENCE
DEBORAH GREENSPAN MARCUS CONANT SOL SILVERMAN, JR
JOHN S. GREENSPAN VIBEKE PETERSEN YVONNE DE SOUZA
Departments of Stomatology (Divisions of Oral Medicine and Oral Biology), Dermatology, and Pathology, Schools of Dentistry and Medicine, University of California, San Francisco, California, USA An outbreak of a new form of oral leucoplakia, found principally on the lateral borders of the tongue, is reported in male homosexuals in the San Francisco area. Many of the patients showed evidence of immunosuppression, and candida was often found in the lesions. The characteristic histology is similar to that of the flat wart of skin. There was immunocytochemical evidence of papillomavirus core antigen in 77% of 30 biopsy specimens, but no papillomaviruses were detected by electron microscopy in samples from 6 randomly selected patients. In 5 of these 6 patients there was evidence of a herpes-type virus. Pneumocystis carinii pneumonia has developed in 8 of 37 patients in a 33-month period. This leucoplakia may presage AIDS, may be associated with both papillomavirus and a herpes-type virus, and may offer clues to the pathogenesis of other forms of oral epithelial hyperplasia and dysplasia.
Summary
Introduction
epidemic of acquired immunodeficiency syndrome (AIDS), consisting of Kaposi’s sarcoma and Pneumocystis carinii pneumonia or other life-threatening opportunistic infections, became apparent in young male homosexuals in San Francisco. At that time we began to see LATE in 1981 the
otherwise healthy men with unusual white lesions of the tongue (hairy leucoplakia, HL). Having first taken it to be candidiasis, we now believe that this condition is a separate entity not previously described in the mouth. We here present preliminary clinical, histopathological, and virological observations in 37 patients with HL followed for up to 33 months. ,
Patients and Methods Patients.-The patients were referred to the oral medicine clinic at the University of California, San Francisco, from the UCSF AIDS Clinical Research Center or by physicians and dentists in the 1.
Gross H, Jellinger K, Kaltenback E, Rett A. Infantile cerebral disorders: clinicalneuropathological correlations to elucidate the aetiological factors. J Neurol Sci
1968; 7: 551-64. 2 Illingworth RS. 3 Chiswick ML,
Why blame the obstetrician? Br Med J 1979; i: 797-801. D’Souza SW, Occleshaw JV. Computerized transverse axial tomography in the newborn. Early Hum Devel 1977; 1: 171-80. 4. Macfarlane JA. Studies in Cerebral Palsy. In: Chalmers I, McIlwaine G, eds. Perinatal audit and surveillance London: Royal College of Obstetricians and Gynaecologists, 1980: 173-87. JA, Redman CWG, Hardie J. The Oxford Cerebral Palsy Study-1978 Results. Devel Med Child Neural 1981; 23: 112. 6 Gupta JM, Tizard JPM. The sequence of events in neonatal apnoea. Lancet 1967; ii: 55-59 7 Dennis J, Chalmers I. Very early neonatal seizure rate: a possible epidemiological indicator of the quality of perinatal care Br J Obstet Gynaecol 1982, 89: 418-26. 8. Lagergren J. Children with motor handicaps. Acta Paediatr Scand 1981; suppl 289. 9 Cornfield J A method of estimating comparative rates from clinical data Application to cancer of the lung, breast and cervix. J Natl Cancer Inst 1951; 11: 1269-75. 10 Woolf B. On estimating the relation between blood group and disease. Ann Hum Genet 1955; 19: 251-53. 11. Fisher RA. The logic of inductive inference. J Roy Stat Soc A 1953; 98: 39-54. 12. Miettinen OS. Estimability and estimation in case-referent studies. Am J Epidemiol 1976; 103: 226-35. 13 Levin ML. The occurrence of lung cancer in man. Acta Un Int Contra Cancrum 1953; 9: 531-41. 5 Macfarlane
city of San Francisco. All patients gave a detailed medical and social history in response to standard questionnaires and had complete physical and oral examinations. When oral white lesions were found, smear and culture for candida were performed. Oral biopsy.-35 biopsy specimens were obtained from 30 patients under local anaesthesia. Routine histopathology and periodicacid/Schiff (PAS) staining was performed on formol-saline-fixed, paraffin-embedded samples. Samples from 6 cases selected at random were also obtained for electron microscopy; these were fixed with 3% glutaraldehydel followed by postfixing in 1% buffered osmic acid2and epon-embedding.3 The sections were stained with lead citrate.4 Immunological studies.-Delayed cutaneous hypersensitivity to purified protein derivative (PPD), candida, mumps, and trichophytin antigens was tested. Phenotypic characterisation and measurement of OKT4 (helper T cells) and OKT8 (suppressor cytotoxic T cells) (Ortho Pharmaceutical, Raritan, New Jersey) of peripheral blood lymphocytes was kindly performed by Dr Conrad Casavant, Department of Laboratory Medicine, UCSF. Papillomavirus antigen.-Evidence for the presence of papillomavirus antigen within the lesion was sought in paraffin-embedded sections by means of a peroxidase-antiperoxidase (PAP) technique with an antiserum to the core antigen of the papillomavirus group. The antiserum was raised in rabbits and the method used, briefly, was as follows: sections were deparaffinised, rehydrated, and washed in 0 - 5 mol/l "tris" buffer (pH 7 - 6). To quench endogenous peroxidase, sections were incubated in 3% hydrogen peroxide for 5 min; next came a 20 min incubation in 20% normal swine serum to reduce nonspecific staining. The sections were then incubated overnight in rabbit antiserum to bovine papillomavirus type 1 (Dako, Santa Barbara, California, PAP Kit TMK521) diluted 1:5000 with "tris" buffer. Control sections were treated in the same manner with the serum of non-immunised rabbits. The secondary antiserum was swine anti-rabbit immunoglobulin diluted 1:100 and placed on the section for 20 min. This was followed by a 20-min incubation with rabbit PAP complex diluted 1:100. The final reaction product was obtained by the use of a substrate solution of 0-3% hydrogen peroxide and 0-02% aminoethylcarbazole (AEC) placed on sections for 40 min. The AEC is oxidised by peroxide to form a red precipitate at the reaction site, thus localising the papillomavirus antigen. The sections were then counterstained in Mayer’s haematoxylin, rinsed, and mounted in glycerol gelatin. All washings between incubations were performed with 0-55 mol/1 "tris" buffer (pH 7 - 6). Control tissues were 7 oral warts (positive control) and 10 specimens of other oral mucosal lesions (4 of epithelial hyperplasia, 4 of candidiasis, and 2 of fibroepithelial hyperplasia) obtained from the files of the oral pathology service, UCSF.
Results
Clinica/.-Between October, 1981, and July, 1984, 37 homosexual men presented with white lesions of the tongue; 14. Walter SD. The distribution of Levin’s measure of attributable risk Biometrika 1975; 62: 371-74. 15. Mantel N, Haenszel W. Statistical aspects of the analysis of data from retrospective studies of disease. J Natl Cancer Inst 1959; 22: 719-48 16. Mantel N. Chi-square tests with one degree of freedom. Extensions of the MantelHaenszel Procedure. J Am Stat Assoc 1963; 58: 690-700. 17. Bakketeig LS, Hoffman HJ, Sternthal PM. Obstetric service and perinatal mortality in Norway. Acta Obstet Gynaecol Scand 1978; 77: 3-19 suppl. 18. Sackett DL. Bias in analytic research. J Chron Dis 1979; 32: 51-63. 19. Alberman E, Stanley F. Guidelines to the Epidemiological Approach. In: Stanley F, Alberman E, eds The epidemiology of the cerebral palsies, (Clin Devel Med no 87). London: Spastics International Medical Publications/Blackwell Scientific Publications, 1984: 172-83. 20. Macdonald D, Grant AM, Pereira M, Boylan P, Chalmers I. The Dublin randomised controlled trial of intrapartum electronic fetal heart rate monitoring. Paper presented at 23rd British Congress of Obstetrics and Gynaecology, Birmingham,
July 13, 1983. N, Stark RI. Cerebral palsy and mental retardation in relation to indicators of perinatal asphyxia. Am J Obstet Gynecol 1983; 147: 960-66. Nelson KB, Ellenberg JH. Obstetric complications as risk factors for cerebral palsy or seizure disorders. JAMA 1984; 251: 1843-48. Stanley FJ Using cerebral palsy data in the evaluation of neonatal intensive care: a warning. Devel Med Child Neurol 1982; 24: 93-94.
21. Paneth 22. 23.