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Biomedical subjects

J D Clemens

Publications and source records attributed to J D Clemens.

139 records · Page 8Linked to original sources
PubMed1983

The BCG controversy. A methodological and statistical reappraisal.

Because of the conflicting results of eight major controlled trials, BCG vaccination against tuberculosis remains controversial despite more than 50 years of use. Suspecting a methodological source for the controversy, we reviewed the scientific and statistical quality of each trial. The analysis showed that (1) although biased allocation of the vaccine appeared an unlikely explanation for the disparate results, adequate demonstration of unbiased detection of tuberculosis was available only for the three trials reporting 75% or greater protective efficacy; and (2) in most trials reporting low efficacy, the results had wide confidence intervals that could not exclude high efficacy, but the trials reporting high efficacy all had narrow confidence intervals that excluded low efficacy. Because the trials with the best methodological quality and greatest statistical precision reported high efficacy, the evidence suggests that BCG can confer a high degree of protection against tuberculosis and that bias or inadequate statistical power may have contributed to the conflicting data.

BCG Vaccine↗
PubMed1983

Rotavirus diarrhoea: an expanding clinical spectrum.

To explore the clinical spectrum of rotavirus diarrhoea in Bangladeshi children, we reviewed surveillance data from randomly selected diarrhoeal cases who were intensively studied at the International Centre for Diarrhoeal Diseases Research--Bangladesh. Twenty-seven (29%) of children aged less than or equal to 4 years excreted rotavirus; rotavirus was the only pathogen isolated from 13 cases. Seven of these 13 cases displayed the typical features of rotavirus diarrhoea: occurrence in infancy, prominent vomiting, watery diarrhoea, and acid stools rarely exhibiting blood or leucocytes. In contrast, six of the 13 cases presented with non-watery diarrhoea. These cases were distinguished by older ages, infrequent vomiting, less acidic stools, faecal blood and leucocytes, and frequent left shifts on peripheral blood examination. We conclude that the clinical spectrum of rotavirus infections may include an invasive diarrhoeal syndrome that differs in several respects from the more widely appreciated watery diarrhoeal syndrome.

Adolescent↗
PubMed1982

A controlled evaluation of the risk of bacterial endocarditis in persons with mitral-valve prolapse.

The absence of controlled evidence and the high prevalence of mitral-valve prolapse have created substantial uncertainty about whether this condition is an important risk factor for bacterial endocarditis. We evaluated this risk in a case-control study of hospital inpatients who had undergone echocardiography and who lacked any known cardiovascular risk factors for endocarditis, apart from mitral-valve prolapse and isolated mitral-regurgitant murmurs. Thirteen (25 per cent) of 51 patients with endocarditis had mitral-valve prolapse, as compared with 10 (seven per cent) of the 153 matched controls without endocarditis. For the 51 matched case-control sets, the odds ratio (8.2; 95 per cent confidence interval, 2.4 to 28.4) indicated a substantially higher risk of endocarditis for people with mitral-valve prolapse than for those without it. This association remained statistically significant when parenteral drug abuse and routine antibiotic prophylaxis preceding dental work and other forms of instrumentation were taken into account. Furthermore, the risk may be higher than is indicated by this study, since 46 per cent of the controls underwent echocardiography for clinically suspected mitral-valve prolapse, suggesting an overrepresentation of mitral prolapse in the control group. The results support the contention that mitral-valve prolapse is a significant risk factor for bacterial endocarditis.

Adult↗
PubMed1982

Metabolism and conjugation of [4-14C]progesterone by bovine liver and adipose tissues, in vitro.

The ability of bovine liver and fat to metabolize progesterone and also to form glucuronide conjugates with these progestins in vitro was investigated. Tissue supernatants were incubated with [4-14C] progesterone, UDP-glucuronic acid, and a NADPH generating system for 5 hr, at 37 degrees C. Steroids were identified by thin-layer chromatography, high performance liquid chromatography, and recrystallization to a constant specific activity. The total original radioactivity which could not be removed by exhaustive ether extraction (presumptive conjugates) was 44.7 +/- 14.2% in liver, 5.0 +/- 3.6% in subcutaneous fat, and 3.7 +/- 2.2% in kidney fat samples. Progestins identified in liver samples include 5 beta-pregnane-3 alpha, 20 alpha-diol (free and conjugate), 5 beta-pregnane-3 alpha, 20 beta-diol (free and conjugate), 3 alpha-hydroxy-5 beta-pregnan-20-one (free and conjugate), 3 beta-hydroxy-5 beta-pregnan-20-one (free), 5 beta-pregnane-3,20-dione (free), and progesterone (conjugate). Progestins identified in both the free and conjugate fractions of subcutaneous fat and kidney fat samples include progesterone, 3 alpha-hydroxy-5 beta-pregnan-20-one, 20 beta-hydroxy-4-pregnen-3-one, and 20 alpha-hydroxy-4-pregnen-3-one. Differences due to sex of bovine used were noted. These results confirm the ability of bovine liver to readily metabolize progesterone and form glucuronide conjugates of these compounds and suggest that adipose tissues take an active role in these actions in cattle.

Adipose Tissue↗
PubMed1979

Pretherapeutic morbidity in the prognostic staging of acute leukemia.

To classify the clinical severity of acute leukemia, we have used the degrees of pretherapeutic infection and hemorrhage to construct a taxonomy containing three "stages". The stages are associated with survival gradients that are clinically and statistically distinctive in both acute lymphoblastic leukemia and acute nonlymphoblastic leukemia. Median survival ranged from 64.0 months for stage 1 to 10.5 months for stage 3 in acute lymphoblastic leukemia, and from 7.1 months for stage 1 to 1.2 months for stage 3 in acute nonlymphoblastic leukemia. The gradients, which persist when other prognostic factors and secular therapeutic changes are taken into account, are more distinctive than those found with other forms of stratification.

Acute Disease↗
PubMedDate not supplied

Prevalence and predictors of the prone sleep position among inner-city infants.

CONTEXT: The prone sleep position is associated with an increased risk of sudden infant death syndrome (SIDS), but few studies have assessed factors associated with the choice of infant sleep position. OBJECTIVES: To describe infant sleep position in a cohort of infants born to predominantly low-income, inner-city mothers and to identify predictors of the prone sleep position in this population. DESIGN: Prospective birth cohort study. PATIENTS AND SETTING: Three hundred ninety-four mother-infant dyads, systematically selected from 3 District of Columbia hospitals between August 1995 and September 1996. Mothers were interviewed shortly after delivery and again at 3 to 7 months postpartum. MAIN OUTCOME MEASURES: Position in which infants were placed for sleep on the night prior to the 3- to 7-month interview. RESULTS: At 3 to 7 months of age, 157 infants (40%) were placed for sleep in the prone position. Independent predictors of prone sleep position included poverty (odds ratio [OR], 1.81; 95% confidence interval [CI], 1.10-2.99), black race (OR, 2.06; 95% CI, 1.05-4.04), presence of infant's grandmother in the home (OR, 1.83; 95% CI, 1.11-3.00), and intent, as measured shortly after delivery, to place the infant in the prone position (OR, 2.28; 95% CI, 1.44-3.60). Importantly, of the 43 mothers who observed their infants in the prone sleep position while in the hospital, 40 (93%) intended to place their infants prone at home. CONCLUSIONS: A substantial proportion of infants in this predominantly low-income population were placed in the prone sleep position. Educational efforts should address both initial intentions and reinforcement of the correct sleep position, once initiated. Hospitals should ensure that healthy newborn infants are placed in the supine sleep position during the postpartum hospital stay.

Humans↗
PubMedDate not supplied

Association between diarrheal duration and nutritional decline: implications for an empirically validated definition of persistent diarrhea.

In an empiric approach to develop the definition of persistent diarrhea, we evaluated the relationship between diarrheal duration and risk of ensuing clinically significant decline in nutritional status, in a cohort of 395 children < 24 mo. Weights were obtained at the onset of diarrhea (wt I) and after three months interval (wt II). The occurrence of an adverse outcome (AO) was defined as a decline of -- 5% in NCHS weight for age (% WFA) between weights I and II or death in this interval. The risk of AO was similar for episodes of / or > 7 days while it was substantially higher in episodes with > 14 days duration (45%) than for shorter duration episodes, relative risk (RR) = 2.5 (p < 0.001). Relative risk remained similar for duration thresholds of 21 (2.3) and 28 days (2.6). As episode durations greater than 14 days are associated with substantial elevation of the risk of clinically cogent sequelae, such episodes may be termed 'persistent' at least in terms of poor prognostic expectations.

Chronic Disease↗
PubMedDate not supplied

Resolving the pneumococcal vaccine controversy: are there alternatives to randomized clinical trials?

It has been more than five years since the relicensure of pneumococcal vaccine. There are few data, however, with which to evaluate the efficacy of pneumococcal vaccine for the conditions constituting current vaccine indications. As a result, recommendations for the use of pneumococcal vaccine remain controversial, and it is widely agreed that further clinical studies should be undertaken. Recommendations for future studies have emphasized the need for randomized clinical trials, which offer the best opportunity to assure scientifically valid results. Generally not considered are the substantial ethical and logistic problems that may impede the conduct of randomized clinical trials capable of resolving the current uncertainty. Observational studies, which include cohort, quasi-cohort, and case-control studies, are alternative approaches for evaluating pneumococcal vaccine. Although lacking the scientific strength of randomized clinical trials, certain observational designs, particularly case-control studies, pose no ethical difficulties and offer logistic advantages that will permit the rapid acquisition of statistically meaningful estimates of the efficacy of the vaccine for patients with current indications. When conducted with careful attention to measures for minimizing bias, observational designs offer attractive alternative strategies for resolving the pneumococcal vaccine controversy.

Bacterial Vaccines↗
PubMedDate not supplied

A voluntary serosurvey and behavioral risk assessment for human immunodeficiency virus infection among college students.

The authors conducted a voluntary serosurvey and educational campaign among 3394 undergraduate students attending the University of Maryland at College Park to determine the prevalence of and risk factors for human immunodeficiency virus type 1 (HIV-1) infection. Two students were seropositive (0.06%, 95% confidence interval 0-0.15%). Both were homosexual men with multiple sexual partners. Despite the low prevalence of infection, potential risk factors for transmission of HIV-1 were common, as assessed by a self-administered anonymous questionnaire. These included a previous sexually transmitted disease (12.6%), male homosexual intercourse (4.8% of men), heterosexual anal intercourse (25.3%), heterosexual intercourse with a person at risk (an HIV-1 infected person, a bisexual man, a parenteral drug user, a female prostitute, or a hemophiliac) (5.2%), multiple sexual partners (21% reported 10 or more lifetime partners), and intravenous drug use (1.3%). Assessment of the efficacy of our program by comparing responses on pre- and post-test questionnaires showed gains in knowledge about heterosexual transmission of HIV-1 and an increase in the reported frequency of condom use 1-2 months after participating in the survey. The authors conclude that HIV-1 infections are occurring among college students but in our study group remain confined to persons with known high-risk behavior; however, practices that may support transmission are common, and programs designed to diminish these behaviors among college students are needed.

Adolescent↗
PubMedDate not supplied

Hepatitis c and cirrhotic liver disease in the Nile delta of Egypt: a community-based study.

Residents of Egypt's Nile river delta have among the world's highest seroprevalence of hepatitis C virus (HCV) infection. To assess the impact of HCV on chronic liver disease, we studied the association between HCV, other hepatitis viruses, and cirrhotic liver disease in a cross-sectional, community-based survey of 801 persons aged > or = 10 years living in a semi-urban, Nile delta village. Residents were systematically sampled using questionnaires, physical examination, abdominal ultrasonography and serologically for antibodies to HCV (confirmed by a third-generation immunoblot assay) and to hepatitis A virus (HAV), hepatitis B virus (HBV), and hepatitis E virus (HEV). The seroprevalence of HCV increased with age from 19% in persons 10-19 years old to about 60% in persons 30 years and older. Although no practices that might facilitate HCV transmission were discovered, the seroprevalence of HCV was significantly associated with remote (> 1 year) histories of schistosomiasis. Sonographic evidence of cirrhosis was present in 3% (95% CI: 1%, 4%) of the population (0.7% of persons under 30 years of age and in 5% of older persons), and was significantly associated with HCV seroreactivity. Our findings are consistent with the hypothesis that past mass parenteral chemotherapy campaigns for schistosomiasis facilitated HCV transmission, and that HCV may be a major cause of the high prevalence of liver cirrhosis in this Nile village.

Adolescent↗
PubMedDate not supplied

Equivocal test results and prognostic staging uncertainties in the evaluation of patients with cancer of the prostate.

In the staging of cancer, equivocal test results may occur in subjectively evaluated imaging procedures whose interpretations raise the possibility of metastases but are too uncertain to rule in or rule out metastatic spread, and in tests whose repetitions in the same patient yield conflicting results about dissemination. We assessed the frequency and prognostic correlates of test results giving equivocal evidence of disseminated (Stage IV) disease in an inception cohort of 280 patients receiving initial treatment for prostatic cancer between 1973-76. Among tests used for clinical staging, lymphangiograms (equivocal in 28 percent of tested patients), bone scans (equivocal in 25 percent of tested patients), and bone radiographs (equivocal in 20 percent of tested patients) most frequently yielded interpretations that equivocally suggested metastatic spread. Eighty-three (45 percent) of the 185 patients without clear-cut dissemination (Stages I-III) had at least one equivocal test result that suggested dissemination and that remained unresolved at the time of selection of therapy. Five-year survival (30 percent) for the 20 patients with local extracapsular spread (Stage III) and multiple equivocal results suggesting dissemination was identical to that for patients with clear-cut dissemination. In contrast, other patients with equivocal dissemination in Stages I-III had survival rates similar to those patients in the same stage and lacking equivocal dissemination. Unresolved equivocal staging results frequently complicate management decisions for patients with prostatic cancer. Survival analyses aid these decisions by demonstrating that equivocal findings of dissemination are prognostically unimportant unless they are multiple and occur in the context of unequivocal extracapsular spread.

Acid Phosphatase↗