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Biomedical subjects

R G Thomas

Publications and source records attributed to R G Thomas.

At least 19 recordsLinked to original sources
PubMed1992

Sample size determination based on Fisher's Exact Test for use in 2 x 2 comparative trials with low event rates.

A collection of sample size tables are presented for designing comparative trials when the event rates p1 and p2 are low. The tables are based on exact power calculations for Fisher's Exact Test. Both one-sided and two-sided alternative hypotheses are considered. A comparison is made between these sample sizes and those obtained by using popular asymptotic approximations.

Clinical Trials as Topic↗
PubMed1992

Concave hymenal variations in suspected child sexual abuse victims.

The purpose of this study was to describe and analyze the characteristics of, and the clinical correlates to, concave hymenal variations in a large number of suspected child sexual abuse victims. Thirteen hundred eighty-three female child and adolescent suspected sexual abuse victims were comprehensively evaluated. Photocolposcopy was used for the anogenital examinations. Concave hymenal variations were found in 174 patients (12.6%). Sixty-one (35.1%) were anterior. Of these, 40 (65.6%) were curved and smooth, and 21 (34.4%) were angular and/or irregular. One hundred (57.5%) were posterior/lateral. Of these, 33 (33%) were curved and smooth, and 67 (67%) were angular and/or irregular. Thirteen patients (7.5%) had multiple hymenal concavities. Posterior/lateral location was associated with penile-vaginal contact (P = .004), penetration (P = .006), stranger perpetrator (P = .032), hymenal rim narrowing (P less than .001), and posterior fourchette abnormality (P = .049). Angular and/or irregular features were associated with penile contact (P = .005), vaginal contact (P = .035), penile-vaginal contact specifically (P less than .001), penetration (P = .046), abnormal general physical examination (P = .018), and hymenal rim narrowing (P less than .001). Logistic regression analysis demonstrated that age-specific prevalence trends for posterior/lateral (P less than .001) and angular and/or irregular (P = .011) concavities were consistent with acquired anatomic findings. An interobserver exercise with five "blinded" raters evaluating photographs of 49 patients showed significant agreement among observers in sorting posterior/lateral and angular concavities into the diagnostic categories "suggestive of trauma" and "trauma."(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Reliability and validity of the Florida Sexual History Questionnaire.

The Florida Sexual History Questionnaire (FSHQ) is a brief 20-item questionnaire designed to assess male sexual dysfunction. The validity and reliability of the scale were examined in 33 diabetic impotent males and 58 nondiabetic, age-equivalent nonimpotent males. The FSHQ was found to have high internal consistency and split-half reliability and significantly discriminated between nonimpotent and impotent subjects. Among diabetic impotent subjects, some of the test items were correlated significantly with physiological measures of sexual functioning. However, the FSHQ failed to discriminate between diabetics diagnosed as having organic or psychogenic impotence. This latter finding is discussed within the context of recent suggestions that it may not be possible to draw a clear dichotomy between organic and psychogenic impotence.

Adult↗
PubMed1989

Stannosis. A report of 2 cases.

Stannosis is a condition in which tin-oxide is deposited in lung tissue after inhalation. Tin-oxide is radiologically visible although there is no tissue reaction to its presence. Two examples of the condition are described. It is of value to recognise the condition and so avoid unnecessary invasive diagnostic procedures.

Humans↗
PubMed1989

Predicting arterial oxygen tension from maximum expiratory flow volume curves in cystic fibrosis.

Measurements of arterial oxygen tension (PaO2) while breathing room air, and maximum expiratory flow volume curves were performed in 34 patients with cystic fibrosis (age range 7-27 years, 24 males and 10 females). Logistic regression was performed using forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), peak expiratory flow rate (PEFR), and forced expiratory flow at 75% of expired vital capacity (FEF75) to model an equation for predicting when PaO2 would be less than 55 mmHg (severe hypoxemia). Equations were modelled using one, two, three, or all four of the variables. For the univariate logistic regression, each of the four variables was a significant (P less than 0.001) predictor for severe hypoxemia. FVC was the best predictor with an R2 = 0.56, sensitivity of 100% (false negative rate = 0%), and a specificity of 88.5% (false positive rate = 27%). The model predicted that patients with an FVC less than 35% of the predicted normal were at risk of having PaO2 less than or equal to 55 mmHg. Adding FEV1, FEF75, or PEFR in various combinations to FVC made the model equation more complicated but did not add significantly to the ability to predict severe hypoxemia.

Adolescent↗
PubMed1989

Regional cerebral blood flow for singers and nonsingers while speaking, singing, and humming a rote passage.

Two groups of singers (n = 12,13) and a group of nonsingers (n = 12) each produced the national anthem by (1) speaking and (2) singing the words and by (3) humming the melody. Regional cerebral blood flow (rCBF) was measured at rest and during each phonation task from seven areas in each hemisphere by the 133Xe-inhalation method. Intrahemisphere, interhemisphere, and global rCBF were generally similar across phonation tasks and did not yield appreciable differences among the nonsingers and the singers.

Adult↗
PubMed1989

Sources of variation in energy intake by men and women as determined from one year's daily dietary records.

Data from a year-long study conducted by the US Department of Agriculture's Beltsville Human Nutrition Research Center were used to identify sources of variation in daily energy intakes. A specific hypothesis was that an inverse relationship exists between past body weight and future energy intake whereas a direct relationship exists between past energy intake and future weight. Daily energy intakes of 29 male (n = 13) and female (n = 16) adult subjects were related through linear-regression analysis to sex (+ for males), age (-), height (+), weight (- for past and present measurements, + for future measurement), data collection method (- for duplicate plate), day of week (+ for Friday and Saturday), and month (+ for May, July, August, December, and January). These relationships were statistically significant (p less than 0.05). The results confirmed the hypothesis and were in general agreement with previously published studies that used larger samples but fewer days of data.

Adult↗
PubMed1989

Modeling for scaling to humans: time to get serious.

The subject matter for this 26th Annual Hanford Life Sciences Symposium evolved from the deliberations of a Task Group on Modeling for Scaling to Humans, which was established in January 1986 through the efforts of the Office of Health and Environmental Research of the Department of Energy (OHER/DOE). Several laboratories that utilize animals in radiobiological research sponsored by the OHER/DOE were extensively reviewed in the spring of 1985, and, as a result, OHER recommended establishment of eight task groups designed for selected purposes. The current membership of the Task Group on Modeling for Scaling to Humans is shown in Table 1; Dr. James A. Mewhinney of the Lovelace Inhalation Toxicology Research Institute has been Chairman since these Task Groups were established. Ms. Judy Mahaffey of Battelle. Pacific Northwest Laboratories served as chairperson for this symposium, and the Task Group membership has served as the Program Committee. The OHER/DOE thanks all of them for their work as members of the Task Group as well as for their arranging such a potentially productive and informative meeting.

Animals↗
PubMed1989

Estimation of human gonadal Pu and Ce concentrations from animal data.

Data were obtained from the literature for gonad and body weights and for the Pu or Ce content of the gonads and body at death for several laboratory animal species, five human Pu injection cases, and 731 human adults exposed environmentally to Pu in fallout. Data for Pu concentration in gonads, liver, and bone samples of 59 male and five female occupational Pu cases (including four completely analyzed whole bodies) were obtained from the U.S. Transuranium Registry. A logarithmic function was used to relate fractional Pu or Ce concentration in testes and ovaries to body weight of the animals and to predict fractional Pu or Ce concentrations in human gonads, [Pu]G . PuB-1 = aBWb, where [Pu]G or [Ce]G is the nuclide concentration in gonads (Bq g-1 of wet weight), PuB or CeB is the nuclide content of the body at death, and BW is body weight (kg). The fractional Pu and Ce concentrations in both the testes and ovaries are inverse and nearly linear functions of body weight. The regression lines of fractional Pu or Ce concentration in testes and ovaries have similar slopes (b = -1.07 +/- 0.14); however, the nuclide concentrations (coefficient a) in ovaries are six times greater than in testes. Extrapolation of the animal data yielded fractional Pu concentrations in human testes and ovaries that agree with those calculated for the occupational cases and those recommended by the International Commission on Radiological Protection. The good agreement between the fractional concentrations of Pu and Ce in the testes and in the ovaries suggests that these data can be substituted in metabolic models of chemically similar elements for which gonadal data are scarce.

Animals↗
PubMed1988

Angiographic and clinical predictors of acute closure after native vessel coronary angioplasty.

To determine predictors of acute coronary closure after PTCA performed with steerable catheter systems, we compared 140 procedures complicated by acute closure and 311 representative successful attempts from 4,772 procedures performed between April 1982 and March 1986. Sixteen clinical, 35 angiographic, and seven procedural variables were analyzed. Multivariate analysis found seven independent preprocedural factors related to closure: stenosis length of 2 or more luminal diameters, female gender, stenosis at a bend point of 45 degrees or more, stenosis at a branch point, stenosis-associated thrombus (filling defect or staining), other stenoses in the same vessel, and multivessel disease. In addition, four procedural factors were found to be associated with closure by univariate analysis: post-PTCA percent stenosis (p less than .001), intimal tear or dissection (p less than .001), use of prolonged heparin infusion (p less than .001), and post-PTCA gradient of 20 mm Hg or more (p = .004). Multivariate analysis of both preprocedural and procedural variables found six factors independently related to closure: post-PTCA percent stenosis, dissection, prolonged post-PTCA use of heparin, branch point location, fixed bend point location, and other stenoses in the vessel dilated. The risk of coronary closure after PTCA has many determinants. While an estimation of risk can be made before performing PTCA, the most powerful predictors of closure can only be assessed during the procedure itself.

Acute Disease↗
PubMed1988

Influence of balloon size on initial success, acute complications, and restenosis after percutaneous transluminal coronary angioplasty. A prospective randomized study.

Restenosis after percutaneous transluminal coronary angioplasty (PTCA) is strongly associated with incomplete initial dilatation. To determine if oversized PTCA balloons would reduce the restenosis rate without increasing the risk of arterial dissection and acute complications, we prospectively randomized 336 patients to receive either smaller or larger balloons. Thirty-four percent of patients had multivessel disease and 18% had multisite dilatation. One hundred sixty-nine patients were randomized to PTCA with a larger balloon and 167 to PTCA with a smaller balloon. Balloon:artery diameter ratios were 1.13 +/- 0.14 in the larger group and 0.93 +/- 0.12 in the smaller group (p less than 0.001). The trial was halted as clinically important differences in acute complications emerged. Emergency bypass graft surgery, usually for the treatment of arterial dissection, was required in 7.1% of patients in the larger balloon group and 3.6% of patients in the smaller balloon group (p = 0.15). Myocardial infarction (Q wave and non-Q wave) complicated 7.7% of procedures in which large balloons were assigned and 3.0% of procedures in which small balloons were assigned (p = 0.056). There were no deaths in either group. The incidence of bypass surgery was 1.7% when the balloon:artery ratio was less than 0.9, 3.1% when the ratio was 0.9-1.1, and 7.8% when it was greater than 1.1. Stepwise logistic regression analysis demonstrated that larger balloon assignment, multiple lesion dilatation, and multivessel coronary artery disease were independent predictors of emergency surgery. Angiographic restudy rates were 50% in the larger group and 60% in the smaller group (p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

Effect of zinc supplementation on the development of cardiovascular disease in the elderly.

Supplemental zinc intake by an ambulatory elderly population was examined. Health questionnaire, electrocardiogram, laboratory, and medication use data from a geriatric health screening program were compared for 69 participants who were taking zinc supplements and 1,832 participants who were not taking zinc supplements during 1985. A major purpose of this study was to evaluate whether ingestion of zinc supplements by elderly persons is a risk factor for development of cardiovascular disease. No association between zinc supplementation and increased risk of developing cardiovascular disease was found for the indices examined. More information is needed to resolve the question of whether or not zinc supplementation is a risk factor for the development of cardiovascular disease. It is important that elderly persons be provided information to evaluate the possible risk versus benefit of taking zinc supplements.

Aged↗
PubMed1988

The relationship of interradicular width and alveolar bone loss. A radiometric study of a periodontitis population.

Contrasting data exist on the relationship between interproximal width and loss of marginal bone in a periodontitis susceptible population. Reports of clinical observations suggest that the prognosis of teeth with minimal interradicular width should be downgraded in periodontal patients. Others indicate a higher prevalence of intrabony lesions in wider interproximal spaces. Radiographs of 114 adult patients with evidence of bone loss consistent with periodontitis were examined. Measurements of interradicular width and the location of the bone margin from the cementoenamel junction were made at 811 interproximal sites using an optical digitizer at 3X magnification. The relationship between bone loss and interradicular width was investigated. The results indicate that as the interradicular width increases, the interproximal bone margin tends to be in a more apical location. No findings supported the contention that bone in a narrow interradicular space is at greater risk in patients who have had periodontitis.

Adult↗
PubMed1988

Dichloroacetate in the treatment of lactic acidosis.

An open, prospective evaluation of the effects of dichloroacetate on morbidity and survival time was done in 29 pediatric and adult patients with lactic acidosis. Dichloroacetate was administered intravenously over 30 minutes as two 50 mg/kg body weight doses separated by 2 hours. Five patients underwent retreatment with two additional drug doses and were considered new cases when analyzing for treatment response. Survival, however, was determined from the time of initial entry into the study. Patients were considered to respond to treatment if arterial lactate concentration decreased at least 20% from the pretreatment level within 6 hours of beginning the first dichloroacetate infusion. Using this criterion, 26 cases responded to therapy with dichloroacetate. For all cases, patients' mean arterial lactate concentration decreased 52% (P = 0.0009), arterial bicarbonate concentration increased 35% (P = 0.0003), and arterial pH increased (P = 0.024) to normal, defined as the range 7.35 to 7.45. Among responders, however, arterial lactate concentration decreased 74% (P = 0.0001), arterial bicarbonate level increased 47% (P = 0.0001), and arterial pH increased (P = 0.0004) to the normal range. Median survival time among responders was 60 hours, compared to 26 hours among nonresponders (P less than 0.001). There was no evidence of toxicity to dichloroacetate.

Acetates↗
PubMed1987

Impact of air filtration on nosocomial Aspergillus infections. Unique risk of bone marrow transplant recipients.

Bone marrow transplant recipients were found to have a 10-fold greater incidence of nosocomial Aspergillus infection than other immunocompromised patient populations (p less than 0.001) when housed outside of a high-efficiency particulate air (HEPA) filtered environment. Multivariate analysis demonstrated that number of infections, age, and graft-versus-host disease severe enough to require treatment were independent risk factors for development of nosocomial Aspergillus infection in this group. The use of whole-wall HEPA filtration units with horizontal laminar flow in patient rooms reduced the number of Aspergillus organisms in the air to 0.009 colony-forming units/m3, which was significantly lower than in all other areas of the hospital (p less than or equal to 0.03). No cases of nosocomial Aspergillus infection developed in 39 bone marrow transplant recipients who resided in this environment throughout their transplantation period compared with 14 cases of nosocomial Aspergillus infection in 74 bone marrow transplant recipients who were housed elsewhere (p less than 0.001). Thus, although bone marrow transplant recipients had an order-of-magnitude greater risk of nosocomial Aspergillus infection than other immunocompromised hosts, this risk could be eliminated by using HEPA filters with horizontal laminar airflow.

Air Microbiology↗
PubMed1987

The effects of continuous phonation on 133xenon-inhalation air curves (of the kind used in deriving regional cerebral blood flow).

Regional cerebral blood flow (rCBF) may be measured with inhalation techniques that use end-expired values of radioactivity to estimate the isotope concentration in arterial blood. These end-expired data are used as an input function in a mathematical equation to derive rCBF. End-expired air is assumed normally to be in equilibrium with the arterial blood at the alveolar surface of the lung during regular (passive) breathing; this assumption may not be valid during continuous phonation. We therefore have analyzed breathing (inhalation/exhalation) patterns and end-expired radioactivity (133Xe) during (1) speaking, (2) singing, and (3) humming of the national anthem, and also during (4) passive breathing. Statistically significant differences in breathing patterns were measured between a group of nonmusicians and two groups of musicians (singers) during the phonation tasks: The nonmusicians breathed more often (and more rapidly) and exhibited less variability in their breathing patterns than did the musicians. Notwithstanding these differences, the shapes of smoothed functions derived from the end-expired values were not influenced appreciably during phonation (except possibly during talking). The latter finding suggests that estimates of rCBF derived with these data should not be confounded seriously because of the continuous phonation.

Adolescent↗
PubMed1987

Effects of behavioral self-management on oral hygiene adherence among orthodontic patients.

Twenty-nine new orthodontic patients and 30 experienced orthodontic patients received either behavioral self-management of toothbrushing and mouth rinsing or an experimental regimen that consisted of prompting by the orthodontist to brush and rinse regularly plus instructions to turn in home care materials during orthodontic visits. Several sets of data showed uniformly high rates of brushing and rinsing among all four groups of subjects. Several data sets also showed significant improvements in oral health status among all four groups. Substantive and methodologic directions for future research are delineated.

Adolescent↗