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Biomedical subjects

B F Polk

Publications and source records attributed to B F Polk.

At least 55 records · Page 3Linked to original sources
PubMed1988

Predictors of decline in CD4 lymphocytes in a cohort of homosexual men infected with human immunodeficiency virus.

Longitudinal data on four visits scheduled at 6 month intervals were available on a cohort of 1,827 homosexual men who were human immunodeficiency virus (HIV) seropositive at entry. To identify predictors of the rate of decline of CD4 T-lymphocytes, we used an autoregressive model that relates CD4 counts to predictor variables, while adjusting for previous CD4 counts. Significant predictors of steeper decline of CD4 counts were high CD8 count, low hemoglobin, low platelets, high serum IgA, high cytomegalovirus (CMV) antibody, and low HIV antibody. Using the fitted model, a subject with an initial deficit of 314 CD4 cells (median value of study sample) with respect to seronegative subjects and with average values in all other predictors is estimated to lose approximately 53 cells in a 6 month period (95% C.I. = 45-61 cells). Contrasting this estimate to the one obtained with similar methods in intravenous drug users, it is suggested that a faster rate of decline is present among i.v. drug users. This analysis provides evidence that several covariates in addition to previous number of CD4 counts have significant predictive power for estimating the decline in CD4 counts in HIV seropositive subjects.

AIDS Serodiagnosis↗
PubMed1987

Risk factors for seroconversion to human immunodeficiency virus among male homosexuals. Results from the Multicenter AIDS Cohort Study.

2507 homosexual men who were seronegative for human immunodeficiency virus (HIV) at enrollment were followed for six months to elucidate risk factors for seroconversion to HIV. 95 (3.8%) seroconverted. Of men who did not engage in receptive anal intercourse within six months before baseline and in the six-month follow-up period, only 0.5% (3/646) seroconverted to HIV. By contrast, of men who engaged in receptive anal intercourse with two or more partners during each of these successive six-month intervals, 10.6% (58/548) seroconverted. No HIV seroconversions occurred in 220 homosexual men who did not practise receptive or insertive anal intercourse within twelve months before the follow-up visit. On multivariate analysis receptive anal intercourse was the only significant risk factor for seroconversion to HIV, the risk ratio increasing from 3-fold for one partner to 18-fold for five or more partners. Furthermore, data for the two successive six-month periods show that men who reduced or stopped the practice of receptive anal intercourse significantly lowered their risk of seroconversion to 3.2% and 1.8%, respectively. Receptive anal intercourse accounted for nearly all new HIV infections among the homosexual men enrolled in this study, and the hazards of this practice need to be emphasised in community educational projects.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Predictors of the acquired immunodeficiency syndrome developing in a cohort of seropositive homosexual men.

In a cohort of 1835 homosexual men who were seropositive for human immunodeficiency virus (HIV) on entry into a prospective study, the acquired immunodeficiency syndrome (AIDS) developed in 59 during a median follow-up of 15 months. We matched 5 seropositive controls to each case according to study center and date of enrollment and performed a case-control analysis to determine factors predictive of AIDS. In a multivariate analysis, a decreased number of T helper lymphocytes, an increased number of T suppressor lymphocytes, a low level of antibody to HIV, a high titer of cytomegalovirus antibody, and a history of sex with someone in whom AIDS developed were independently associated with subsequent AIDS. Separate analyses of risk factors for Kaposi's sarcoma and opportunistic infections failed to support previously reported associations between the use of nitrites or an elevated cytomegalovirus-antibody titer and Kaposi's sarcoma. These variables may be markers rather than determinants of disease progression. A vigorous antibody response to HIV infection may confer at least temporary protection against the progression of immunodeficiency to AIDS, or a low level of antibody to HIV may reflect a later stage of infection. The increased risk associated with a history of sex with someone in whom AIDS developed may indicate earlier infection in cases or infection with a more virulent strain of HIV. These results may be useful in counseling HIV-seropositive persons and in designing studies of clinical interventions.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Predictive value of minor anomalies: II. Use in cohort studies to identify teratogens.

Cohort studies of putative human teratogens can identify the full spectrum of phenotypic effects, including both major malformations and minor anomalies. Cohort studies which include the much more common minor anomalies make it possible to use a relatively small number of exposed and unexposed infants to identify an increase in the frequency of malformations. We evaluated this use of minor anomalies in a cohort study of newborn infants who had been exposed in utero to three putative teratogens: insulin-dependent diabetes mellitus in the mother and the use of the anticonvulsant phenytoin and exogenous sex hormones by the mother. In addition, the reproducibility of identifying minor anomalies was tested by comparing the results of examinations by two independent observers of 444 unexposed infants. The frequency of minor anomalies was increased among infants of diabetic mothers. However, the reproducibility of identifying minor anomalies was poor. We conclude that the examination of teratogen-exposed infants for minor anomalies cannot be used in epidemiologic studies of putative teratogens unless special efforts are made to maximize consistency in the identification of these features.

Abnormalities, Drug-Induced↗
PubMed1987

Delayed hypersensitivity skin testing and anergy in a population of gay men.

Anergy is almost universal among patients with the acquired immunodeficiency syndrome (AIDS). To determine the prevalence and correlates of anergy in a population at risk for AIDS, we performed skin tests in 1120 gay men who were enrolled in a prospective study of the natural history of human immunodeficiency virus (HIV) infection. Anergy, defined as no induration to any of four intradermal antigens, was present in 12%. Individually, no induration was detected in response to tetanus toxoid (41%), mumps (28%), candida (47%), and trichophyton (72%). Anergy was strongly associated with the presence of antibody to HIV and with a reduced number of T helper lymphocytes, but not independently with generalized lymphadenopathy, the number of reported male sexual partners in the previous 2 years, the number of T suppressor lymphocytes, or with high titers of antibodies to cytomegalovirus. Nine percent of HIV antibody-negative subjects and 20% of antibody-positive subjects were anergic; anergy is not specific for serologically documented HIV infection in this population. Skin testing with only tetanus toxoid, candida, and mumps antigens may be sufficient to detect anergy. In the presence of HIV antibody, the ability of anergy to predict progressive immunodeficiency remains to be determined.

AIDS-Related Complex↗
PubMed1987

Treatment of cytomegalovirus retinitis with ganciclovir.

Eighteen immunocompromised patients with cytomegalovirus (CMV) retinitis were treated with ganciclovir, an investigational antiviral drug. CMV retinitis in association with acquired immune deficiency syndrome (AIDS) developed in 17 patients; CMV retinitis developed in one patient after cardiac transplantation. Fourteen patients responded to ganciclovir treatment with improvement in CMV retinitis. In 11 patients, the response was classified as complete; in three patients, the response was partial. Continued improvement in the retinitis was often seen while the patient was on maintenance treatment. Maintenance ganciclovir therapy was required; relapse occurred in five of seven patients in whom ganciclovir treatment was interrupted. The major limiting toxic side effect of ganciclovir was neutropenia, which necessitated temporary discontinuation of ganciclovir in five patients but was reversible in all cases. Ganciclovir appears to be an effective therapy for CMV retinitis, but chronic maintenance therapy is required.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Dermatologic findings associated with human immunodeficiency virus infection.

Both human immunodeficiency virus (HIV) infection and acquired immunodeficiency syndrome (AIDS) are associated with an increased prevalence of several dermatologic diseases. We studied healthy homosexual men with negative reactivity to HIV antibody, homosexual men without AIDS but with positive reactivity to HIV antibody, and homosexual men with AIDS to compare the prevalence of dermatologic disease in these groups. We found that five cutaneous disorders were increased in persons with HIV infection. Oral hairy leukoplakia was increased both in seropositive subjects without AIDS and in subjects with AIDS. Condylomata acuminata and seborrheic dermatitis were slightly increased in seropositive non-AIDS subjects and significantly increased in the AIDS group. Molluscum contagiosum and oral candidiasis were increased only in the AIDS group.

Acquired Immunodeficiency Syndrome↗
PubMed1987

The Multicenter AIDS Cohort Study: rationale, organization, and selected characteristics of the participants.

The Multicenter AIDS Cohort Study was designed to elucidate the natural history of the infection causing acquired immunodeficiency syndrome (AIDS), identify risk factors for occurrence and clinical expression of the infection, and establish a repository of biologic specimens for future study. A variety of recruitment techniques, including special assurance of confidentiality, were used to enroll participants. Nearly 5,000 homosexual men volunteered for semiannual interview, physical examination, and laboratory testing in four metropolitan areas. A significant majority of these men in each center (69-83%) reported having 50 or more lifetime sexual partners, and over 80% had engaged in receptive anal intercourse with at least some of their partners in the previous two years. By the time of the participants' initial evaluation (April 1984-April 1985), infection with the human immunodeficiency virus (HIV) had occurred in higher proportions of men in Los Angeles (51%) and Chicago (43%) than in Baltimore/Washington, DC (31%) and Pittsburgh (21%), presumably as a result of the higher number of partners and proportion with whom these men had engaged in high-risk practices (e.g., receptive anal intercourse). Follow-up evaluations are underway in this comprehensive longitudinal investigation of HIV infection.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Risk factors for surgical-wound infection following cardiac surgery.

In a prospective study of 1,009 adult patients undergoing elective cardiac surgery at The Johns Hopkins Hospital, we determined the association between a variety of preoperative and operative parameters and the risk of postoperative sternal- or mediastinal-wound infection. Of the parameters reflecting nutritional state, only one, reduced level of albumin in serum, was significantly associated with sternal- or mediastinal-wound infection by univariate analysis. The final multiple logistic regression analysis indicated that four variables were significant (P less than .05) independent predictors of sternal- or mediastinal-wound infection: obesity (relative odds = 3.8; 95% confidence limits = 1.9-7.5), diabetes mellitus (relative odds = 2.6; 95% confidence limits = 1.4-4.8), length of hospital stay before surgery greater than five days (relative odds = 2.0; 95% confidence limits = 1.2-3.5), and current cigarette smoking (relative odds = 1.8; 95% confidence limits = 1.1-3.1). Of these variables, perhaps only smoking will lend itself routinely to attempts at intervention.

Aged↗
PubMed1987

The prevalent cohort study and the acquired immunodeficiency syndrome.

The acquired immunodeficiency syndrome (AIDS) is caused by a retrovirus, the human immunodeficiency virus (HIV). A rapid and convenient method to identify additional cofactors or risk modifiers and markers of disease progression is to study a cohort prevalent with HIV antibody. However, because the time of viral infection is usually unknown in the cohort, there are several potential sources of bias. Three sources of bias in a prevalent cohort study are identified assuming a proportional hazards model: onset confounding, differential length-biased sampling, and frailty selection. A number of problems in the interpretation of results on markers from a prevalent cohort also are considered. It is concluded that risk estimates derived from a prevalent cohort are not directly comparable to risk estimates derived from an incident cohort.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Reproducibility and predictive values of routine blood pressure measurements in children. Comparison with adult values and implications for screening children for elevated blood pressure.

A study of the variability of blood pressure was conducted among a total of 780 Massachusetts children, 335 children in East Boston and 445 children in Brookline, ages 8-18 years. All children had their blood pressure measured with a standard mercury sphygmomanometer in a school setting on four visits one week apart with three measurements per visit. In East Boston, repeat measurements were made for the same children for four consecutive years. A nested random effects model was used to estimate between- and within-visit variance components. For children aged 8-12 years, these were, respectively, 33.1, 12.0 in boys and 31.2, 11.1 in girls for systolic blood pressure and 57.7, 21.3 in boys and 56.6, 22.6 in girls for systolic muffling blood pressure (Korotkoff phase 4). For children aged 13-18 years of age, they were, respectively, 41.1, 11.8 in boys and 35.2, 12.2 in girls for blood pressure and 40.6, 15.5 in boys and 36.1, 11.4 in girls for diastolic blood pressure (Korotkoff phase 5). Within-person variability for systolic pressure was comparable to previously published data for 434 white adults ages 30-49 years not on antihypertensive medications; however, within-person variability for diastolic pressure was considerably higher in the children, accounting for over 75% of total variability among 8-12-year-old children, compared with 27% for adults. No meaningful effects of age, sex, or blood pressure level on variability of systolic pressure were found. However, age and level of blood pressure each had a large and independent inverse association with variability of diastolic pressure; variance components for younger children (ages 8-12 years) and children with low diastolic pressure (less than 60 mmHg) were approximately twice as large as for older children (ages 13-18 years) and children with diastolic pressure greater than or equal to 60 mmHg, respectively. Finally, predictive value estimates of blood pressure are provided for particular age-sex groups to enable one to efficiently identify children whose true mean level of blood pressure exceeds the 90th percentile for their age-sex group with minimum misclassification. Because of the substantial variability of diastolic pressure in young children, resulting in relatively low predictive value estimates, systolic pressure (either alone or in combination with diastolic pressure) may be more useful as the primary tool for screening children under age 13 years for high blood pressure.

Adolescent↗
PubMed1987

Detection of early antibodies in human immunodeficiency virus infection by enzyme-linked immunosorbent assay, Western blot, and radioimmunoprecipitation.

A current concept of the serological response to human immunodeficiency virus (HIV) infection in humans is that antibodies to core antigens (p55, p24, and p15) are detectable earlier during initial stages of antibody production than antibodies against envelope antigens (gp160, gp120, and gp41). Comparative studies of Western blot (immunoblot), radioimmunoprecipitation assay (RIPA), and enzyme-linked immunosorbent assay (ELISA) during initial antibody production are limited to case reports and have not resolved the issue. Thirty of the 37 participants who are part of a prospective study had at least one specimen that was negative for anti-gp41 but had one or more other bands on Western blot. Twenty-seven of these 30 specimens were reactive for anti-gp120/160 in the RIPA. Of the same 30 specimens, kits from Bionetics identified 2 (7%), ElectroNucleonics 4 (13%), Abbott 13 (43%), Du Pont 25 (83%), and Genetic Systems 25 (83%). All participants had evidence of serological progression by Western blot, including a gp41 band, on subsequent visits; the ELISA kits of all manufacturers identified these later specimens with greater accuracy. These data show that the RIPA detects anti-envelope antibodies that may be not detectable by Western blot and that the production of anti-envelope antibodies approximately parallels the production of anti-core antibodies. The false-negative results by ELISA would permit transmission of HIV by blood transfusion from donors in early stages of infection. The sensitivity of licensed ELISA kits should be improved to identify antibody as soon as possible after infection.

Acquired Immunodeficiency Syndrome↗
PubMed1987

The association of postural changes in systolic blood pressure and mortality in persons with hypertension: the Hypertension Detection and Follow-up Program experience.

Participants in the Hypertension Detection and Follow-up Program (HDFP) were classified on the basis of baseline standing minus sitting systolic blood pressure into four groups (less than or equal to -20 [group 1], -19 to 0 [group 2], 1 to 20 [group 3], and greater than 20 mm Hg [group 4]) to study 5 year mortality. Group 1, 3.3% of the total, contained those participants who had postural hypotension. The 5 year total and age-adjusted mortality rates for these groups were significantly different (p less than .04), with group 1 having the highest rates. To account for the possible confounding effects of certain baseline risk factors--age, sex, race, prior antihypertensive treatment, randomization group, diabetes, end-organ damage, sitting diastolic and systolic blood pressures, pulse, hematocrit, smoking status, and relative weight (percent of ideal weight)--in assessing group differences in mortality rates, a multiple logistic model was used. Relative weight proved to be a confounding factor for the association of drop in postural systolic blood pressure with mortality. However, there is an interaction between history of diabetes and postural change in systolic blood pressure. Thus, postural hypotension may indicate a poor prognosis in diabetic hypertensive patients.

Actuarial Analysis↗