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Biomedical subjects

W D Johnson

Publications and source records attributed to W D Johnson.

At least 73 records · Page 4Linked to original sources
PubMed1995

Syphilis screening in out-of-hospital care.

To estimate the rates of syphilis infection in inner-city patients managed by prehospital providers, a convenience sampling of prehospital patients who had intravenous lines initiated was screened for syphilis over a nine-month study period from February 1992 through October 1992. In a university-affiliated inner-city emergency department served by a city ambulance company, patients 18 years of age or older transported via ambulance who had had intravenous lines initiated at the scene or en route had a Venereal Disease Research Laboratory (VDRL) and microhemagglutination-Treponema pallidum (MHA-TP) drawn and performed by the state laboratory as a routine serological test. If the results were reactive with no previous history of syphilis recorded in the state registry, the state health department and/or one of the authors of this study contacted the patient for follow-up treatment. Age, race, sex, and diagnostic category (medical, surgical/obstetric, or neuropsychiatric) were recorded. Results were checked with the state syphilis registry. Latent syphilis was defined as a reactive VDRL and MHA-TP with no prior history of infection or record of infection in the state syphilis registry. Chi-squared test was used in statistical analysis for comparisons among ages, races, and sexes, with P > .05 considered significant. Three hundred two subjects 18 years of age and older consenting to a screening VDRL and MHA-TP had serum drawn. Two hundred seventy-nine patients were enrolled in the study after 23 patients were excluded because of improper data collection or insufficient serum collection. There were 174 men (63%) and 105 women (37%), with 73 white (26%) and 199 African-Americans (71%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Tympanic membrane thermometry in the care of out-of-hospital patients.

STUDY OBJECTIVES: To determine the effectiveness of tympanic membrane (TM) thermometry in the out-of-hospital setting and to characterize the patients with abnormal out-of-hospital temperatures. DESIGN: Prospective, randomized, single-month study. SETTING: Inner city. PARTICIPANTS: Subjects transported by ambulance for whom consent was obtainable. RESULTS: TM probes set to rectal equivalent were assigned to three of the ambulance units of the local health department on randomly selected shifts during August 1992, one half at night and one half during the day. Simultaneous left and right ear temperatures at the scene and at the hospital, ambient temperatures, and patient's hospital temperatures were recorded. Other data recorded included each patient's mental status, activity level, and environment temperature. Paramedics noted whether they suspected a temperature problem before using the probe and whether any treatment was directed toward the patient's temperature. Regression, bias analysis, and chi 2 testing were performed; P was considered significant if it was less than .05. Right and left ear TM temperatures were correlated both at the scene and at the hospital (r = .91 and .92, respectively). TM temperatures and hospital temperatures were also correlated (r = .83 for right ear and .78 for left ear). Evaluation of agreement indicated that TM and hospital methods were equal, with a bias of -0.55 degrees F for oral and +0.66 degrees F for rectal temperatures. Thirty-two subjects (17%) were hyperthermic at the scene; of these, 9 of 32 (28%) were suspected before use of the probe. The paramedics initially treated 5 of the 9 suspected to have a temperature-related problem before using the probe and none of the 23 who were not suspected before using the probe (chi 2, P < .001). CONCLUSION: The TM probe functioned well despite a month of vigorous handling. Temperature correlation with the gold standard and between ears was acceptable in this setting. Presence of the probe did not help with the management of hyperthermic patients in this study.

Adolescent↗
PubMed1995

Some applications of the analysis of multivariate normal data with missing observations.

Methods are proposed for the analysis of data from a multivariate normal distribution when observations are missing completely at random on some of the variates. Park (1) proved the equivalence of the solutions given by maximum likelihood and generalized estimating equations when data are complete and an unstructured covariance is assumed. He suggested that generalized estimating equations may be used if sample sizes are large relative to the amount of missing data and the estimated covariance matrix is positive definite. We give several examples indicating that the estimating equations give results similar to those of maximum likelihood when smoothing of the covariance matrix to eliminate nonpositive definiteness is not encountered as, for example, under an assumption of exchangeable correlation. Generalized linear models are formulated that are appropriate for a wide class of experimental plans.

Blood Coagulation↗
PubMed1995

Double-repetitive-element PCR method for subtyping Mycobacterium tuberculosis clinical isolates.

We describe a rapid method for subtyping Mycobacterium tuberculosis based on PCR amplification of segments located between two distinct DNA repetitive elements. This method, double-repetitive-element PCR, classified 46 clinical isolates as having 25 distinct patterns; the conventional restriction fragment length polymorphism analysis classified the same isolates as having 23 distinct patterns. The double-repetitive-element PCR is a rapid subtyping method that has a discriminating power similar to that of the restriction fragment length polymorphism method.

Bacterial Typing Techniques↗
PubMed1995

Transmission of multidrug-resistant tuberculosis in a large urban setting.

Multidrug resistance has become an increasingly important problem in the control and prevention of tuberculosis in large urban centers. Although several small outbreaks of multidrug-resistant (MDR) tuberculosis in New York City have been reported, the increase in the number of cases is not fully explained by these recognized outbreaks, and the modes of transmission have not been clearly delineated. Transmission patterns of MDR tuberculosis in New York City, therefore, were studied by stratifying Mycobacterium tuberculosis isolates from 167 newly diagnosed tuberculosis patients according to their DNA restriction fragment length polymorphisms (RFLP). Forty-three (34%) of 127 drug-susceptible isolates and 19 (79%) of 24 multidrug-resistant isolates had RFLP patterns representing possible recent exogenous infection (primary tuberculosis). Patients who had such isolates were more likely to be seropositive for human immunodeficiency virus (58%; p < 0.05), non-Hispanic black (56%; p < 0.005), U.S.-born (57%; p < 0.001), and have MDR tuberculosis (79%; p < 0.0005). In a logistic regression model, primary tuberculosis remained significantly associated with MDR tuberculosis and black race. In contrast to previous reports, in New York City recent exogenous transmission accounts for most new cases of multidrug-resistant tuberculosis.

Adult↗
PubMed1995

Effect of synchronized, systolic, lower body, positive pressure on hemodynamics in human septic shock. A pilot study.

The pathophysiologic disturbance observed in volume-resuscitated patients with septic shock is primarily that of hyperdynamic circulation with a markedly reduced systemic vascular resistance. We hypothesized that external, mechanically applied, phasic lower body positive pressure could increase systemic vascular resistance and, thus, blood pressure in patients with refractory septic shock. A total of nine studies were performed on seven patients with septic shock refractory to volume resuscitation and vasopressors. All pre-existing therapies were continued unaltered during the study period. Phasic lower body positive pressure was produced by rapid synchronized inflation of pneumatic fabric cuffs fitted around each lower extremity. The cuffs were inflated for 200 ms to a pressure of 150 mm Hg, and the timing of inflation was adjusted to coincide with the peak systolic arterial pressure. Hemodynamic measurements were obtained at baseline and after 15 min of phasic lower body positive pressure. This off-on cycle was repeated twice for each study. Phasic lower body positive pressure increased mean arterial pressure by 12% and cardiac index by 14% (p = 0.01) over baseline (p < or = 0.001). Heart rate, central venous pressure, pulmonary capillary wedge pressure, arterial pH, arterial pO2, and mixed venous pO2 were unchanged. Synchronized external systolic compression of the lower extremities increased mean arterial pressure and cardiac output in seven patients with refractory septic shock. This hemodynamic improvement was independent of changes in calculated systemic vascular resistance.

Adult↗
PubMed1994

Cyclospora infection in adults infected with HIV. Clinical manifestations, treatment, and prophylaxis.

OBJECTIVE: To determine the prevalence and clinical manifestations of Cyclospora in Haitians infected with human immunodeficiency virus (HIV) who have diarrhea and to evaluate therapy and prophylaxis. DESIGN: Cohort study. From 1990 to 1993, stool samples were collected from adults seropositive for HIV who had had diarrhea for at least 3 weeks. SETTING: A clinic in Haiti. INTERVENTIONS: Stool samples were examined for enteric protozoa after acid-fast staining. Patients with Cyclospora infection were treated with trimethoprimsulfamethoxazole (160 mg and 800 mg, respectively) given orally four times a day for 10 days. After completion of therapy, patients were evaluated weekly and re-treated if clinical and parasitologic recurrences occurred, followed by trimethoprim-sulfamethoxazole prophylaxis three times a week. RESULTS: 804 of 2400 patients (33%) seropositive for HIV had a history of chronic or intermittent diarrhea; 502 of these 804 patients (62%) currently had diarrhea, and 450 patients each provided two stool specimens for examination. Enteric protozoa identified included Cryptosporidium (30%), Isospora belli (12%), Cyclospora species (11%), Giardia lamblia (3%), and Entamoeba histolytica (1%). Forty-three patients with diarrhea and Cyclospora infection were studied; their symptoms were indistinguishable from those seen in patients with isosporiasis or cryptosporidiosis. In all patients, diarrhea ceased and results from stool examinations were negative within 2.5 days after beginning oral trimethoprim-sulfamethoxazole therapy. Recurrent symptomatic cyclosporiasis developed in 12 of 28 patients (43%) followed for 1 month or more, but it also responded promptly to trimethoprim-sulfamethoxazole therapy. These 12 patients received trimethoprim-sulfamethoxazole three times a week as secondary prophylaxis, with only a single recurrence after 7 months. CONCLUSION: Cyclospora infection is common in Haitian patients with HIV infection, responds to trimethoprim-sulfamethoxazole therapy, and has a high recurrence rate that can be largely prevented with long-term trimethoprim-sulfamethoxazole prophylaxis.

AIDS-Related Opportunistic Infections↗
PubMed1994

Fitting multivariate polynomial growth curves in two-period crossover designs.

We discuss the statistical analysis of data from two clinical trials using crossover designs. In both studies, response was observed repeatedly over time in each treatment period. The first study involves repeated measurements of a single response variable whereas the second involves bivariate response. Methods are described for fitting polynomial growth curves to achieve data reduction in a two-stage approach to the analysis of crossover designs. Thus, a multivariate parametric analysis frequently can be conducted even when the sample sizes are somewhat small as is the case in many crossover designs. Hypotheses that are usually of interest in crossover designs can be tested in the second stage of the analysis. Methods for testing the multivariate general linear hypothesis as a basis for statistical inference in such problems are discussed.

Allium↗
PubMed1994

Cytokines in the treatment of leishmaniasis: from studies of immunopathology to patient therapy.

The genus Leishmania, an obligate intramacrophage parasite, causes a wide spectrum of clinical diseases. It is worldwide in distribution and causes 20 million new cases annually with an at risk population of approximately 1.5 billion persons. The most severe forms are associated with high morbidity, mortality and relapses with conventional therapy. The therapeutic issues and responses to standard and alternative therapies are reviewed. Recent developments in molecular biology and immunology methods employed in the study of leishmaniasis have defined an intricate interaction of the parasite with host immune system. Perturbation of the host immune responses may be part of the survival mechanisms of Leishmania. In murine model, the finding of T helper cells that differ by their panel of cytokines has allowed a more precise definition of immunopathogenesis of leishmaniasis. Preliminary data from leishmaniasis patients lend support to this concept of altered immunomodulation. Furthermore, the data from leishmaniasis patients lend support to this concept of altered enhancement of therapeutic response by interferon-gamma has provided a new approach for treatment of patients using recombinant cytokines and for the study of the disease. Current research for early diagnosis, alternative therapies and need for vaccines are reviewed in the context of the immunopathology of leishmaniasis.

Animals↗
PubMed1994

Granulocyte-macrophage colony-stimulating factor in combination with pentavalent antimony for the treatment of visceral Leishmaniasis.

The efficacy of GM-CSF was investigated in 20 neutropenic patients (< 1500 neutrophils/microliters) with acute visceral leishmaniasis due to Leishmania chagasi. Patients were randomized to receive either GM-CSF, 5 micrograms/kg daily (intravenously or subcutaneously), or placebo for ten days, in combination with pentavalent antimony, 10-20 mg/kg daily for 20 days. Neutrophil counts were significantly greater on days 5 and 10 of treatment in the GM-CSF group compared with the placebo group (p < 0.02). Eosinophil and monocyte counts were also significantly increased in the GM-CSF group at day 10 (p < or = 0.03). Interestingly, at day 30, platelet counts were significantly increased in the GM-CSF group on days 5 and 10 (p = 0.04 and 0.02, respectively). Patients in the GM-CSF group experienced fewer secondary bacterial or viral infections than placebo patients. Infections occurred in only three patients given GM-CSF compared with eight patients given placebo (p < 0.04). All patients had complete resolution of disease symptoms at three months. Few adverse events were recorded. GM-CSF given subcutaneously at a dose of 5 micrograms/kg daily for ten days was well tolerated, reversed neutropenia rapidly and reduced the number of secondary infections in patients with leishmaniasis.

Adolescent↗
PubMed1994

Helicobacter pylori-associated gastritis and the ascorbic acid concentration in gastric juice.

Patients infected with Helicobacter pylori have abnormally low ascorbic acid concentration in gastric juice. Low vitamin C intake and Helicobacter pylori infection have been related to an increased risk of gastric carcinoma. This report examines the association between ascorbic acid and Helicobacter pylori in patients referred for upper gastrointestinal endoscopy. Elevated gastric pH and the damage to the gastric surface epithelium were inversely associated with the ascorbic acid concentration in gastric juice. We postulate that these two factors mediate the ascorbic acid-decreasing effect of Helicobacter pylori. Patients with nonpremalignant conditions (normal gastric histology, diffuse antral gastritis, or duodenal ulcer) had lower gastric pH, less damage to the gastric epithelium, and higher levels of ascorbic acid in gastric juice than patients with atrophic gastritis, intestinal metaplasia, or dysplasia.

Adolescent↗
PubMed1994

Testing specific hypotheses by fitting underlying distributions to categorical data.

The problem of estimating parameters and testing hypotheses pertaining to categorical data is well known in statistical analysis. Much of the literature on the subject specifies and fits linear models to multinomial data using methods such as weighted least squares. This article describes maximum-likelihood estimation and likelihood ratio tests for ordered categorical response variates with either discrete or continuous underlying probability distributions. Emphasis is on fitting and making inferences about parameters of mixture distributions, especially mixtures of normal distributions. Goodness-of-fit tests are given to check the adequacy of the fitted distributional models.

Data Interpretation, Statistical↗
PubMed1994

Diagnostics for the multivariate linear model analysis of 2 x 2 crossover designs.

The multivariate linear model Y = X beta + epsilon is used to analyze data in 2 x 2 crossover designs with either univariate or multivariate response. Diagnostics are performed on estimating the effect of interest formulated as C beta U and on testing the general linear hypothesis C beta U = k. The multivariate Cook's distance is extended to be the influence measure by incorporating the contrast matrix C and the transformation matrix U, and magnitude of F(1)-F, the difference between the F approximation of a multivariate test statistic, is proposed as a measure to detect influential observations for testing the hypothesis C beta U = k. Both measures prove to be very useful because the diagnostics are now associated with estimating and testing effects of interest in the context of the experimental design.

Biopharmaceutics↗
PubMed1994

Recombinant human granulocyte-macrophage colony-stimulating factor reverses neutropenia and reduces secondary infections in visceral leishmaniasis.

Twenty-four patients with acute visceral leishmaniasis and leukopenia (< 1500 neutrophils/mm3) due to Leishmania chagasi were studied, 4 in an open-label pilot study and 20 in a double-blind, placebo-controlled trial. Patients received granulocyte-macrophage colony-stimulating factor (GM-CSF), 5 micrograms/kg daily, or placebo for 10 days, plus 10-20 mg/kg pentavalent antimony daily for 20 days. In GM-CSF recipients, neutrophil counts increased threefold and fourfold over baseline at 5 and 10 days, respectively, and were significantly higher than those in placebo recipients (P < .02). Eosinophil and monocyte counts were significantly increase in GM-CSF recipients at 10 days (P < or = .03). Secondary infections occurred in 3 GM-CSF and in 8 placebo recipients (P = .04). All patients had complete resolution of their leishmaniasis at 3 months. Few adverse events were recorded. GM-CSF, 5 micrograms/kg daily for 10 days, was safe, rapidly reversed neutropenia, and reduced the number of secondary infections in patients with leishmaniasis.

Adolescent↗
PubMed1994

Feasibility and cohort development for HIV vaccine trials in Haiti.

Human immunodeficiency virus (HIV) infection is spreading rapidly in Haiti with HIV seroprevalence rates of 10% and 3% in urban and rural areas, respectively. Since 1985, heterosexual transmission has been the primary mode of acquisition of HIV. From 1981 to the present, the Cornell-GHESKIO unit in Port-au-Prince, Haiti, has developed the infrastructure to recruit and retain large cohorts of individuals at risk for HIV infection. Among the populations studied, couples discordant for HIV infection appear most suitable for eventual HIV phase III vaccine trial. This paper describes the recruitment, retention, and characteristics of the discordant-couples cohort, as well as the limitations of interventions aimed at behavior modification.

AIDS Vaccines↗