Search PubMed⌕ Search

Biomedical subjects

G W Williams

Publications and source records attributed to G W Williams.

At least 73 records · Page 4Linked to original sources
PubMed1982

Analysis of survival of end-stage renal disease patients.

Traditional life-table analysis of differences in patient survival for various end-stage renal disease (ESRD) treatment modalities ignore the fact the ESRD patients face sequential risks because they frequently experience more than one mode of therapy. A modification of the usual life-table analysis is suggested as being more appropriate. This modified method takes into account the "time-to-treatment" bias, which, in this instance, is the time spent on the first modality of treatment (that is, center dialysis). The survival data of more than 2,000 ESRD patients in the State of Michigan during the 5-year period, 1974 to 1978, are used to illustrate this method.

Adolescent↗
PubMed1982

A blood ordering strategy for hospital blood banks derived from a computer simulation.

The ultimate goal of a hospital blood bank inventory control programs is to reduce wastage of blood products and unnecessary use of laboratory services without jeopardizing patient safety. The development of a practical blood ordering policy at the hospital level is an integral part of any such program. In order to explore various blood ordering options in detail, a computer simulation of a hospital blood inventory was used to assess the impact on blood band performance measures of reductions in group O and non-group-O levels from baseline levels, assuming both a 21-day and 35-day shelf life. On the basis of data derived from this study showing that such inventory reductions accompanied by partial protection of the group O inventory will not result in significant shortages, a practical strategy was developed for establishing optimal target inventory levels for a hospital on an empirical basis. These target levels can serve as a guide for subsequent blood ordering. A step-by-step approach for analyzing a hospital blood inventory control program is then suggested, accompanied by an action plan for implementing change which incorporates the experimentally-derived blood ordering strategy. Adherence to this plan should result in a low outdate rate, a reduction in unnecessary cross-matching, and greater availability of blood for those patients with a legitimate need for it.

ABO Blood-Group System↗
PubMed1982

Brainstem dysfunction in the infant apnea syndrome.

Thirty-six infants identified as infant apnea syndrome (IAS) and 25 controls with a comparable age distribution were evaluated with Brainstem Auditory Evoked Potential (BAEP) testing. There was a significant predilection for leftsided BAEP abnormalities in IAS patients. Fifteen IAS patients had bilateral abnormalities, and of the 21 IAS patients with unilateral abnormalities, 17 had abnormalities on the left side (p less than 0.01 by McNemar's test). Significant differences (p less than 0.05 by analysis of covariance adjusting for age) between normal controls and IAS infants were found for peak latencies I, III, and V, and amplitude III. Linear regression analyses of the above parameters versus age in months for normal controls were constructed with 68% and 95% prediction interval bands to permit analysis of individual data points. Data points from the IAS infants with bilateral BAEP abnormalities have been plotted on these linear regression curves. No single measurement of latency or amplitude is abnormal in the majority of IAS infants, but many of the individual points fall outside of the 95% prediction curve.

Brain Stem↗
PubMed1982

Analyte stability in clinical chemistry quality control materials.

Maximum stability of analytes in chemistry control materials is desired. Stability testing is customarily performed by manufacturers, both prior to distribution of products and during the period following distribution when the products are in the field. Users and evaluators of such materials periodically have reported on experienced stability of various analytes in distributed manufactured products. A wide variety of both testing protocols and definitions of acceptable stability have characterized published reports on the topic. In the present review, we summarize published studies on control material stability in clinical chemistry, review criteria employed to define instability, and present an approach to evaluating stability of analytes involving both statistical and clinical criteria.

Alanine Transaminase↗
PubMed1982

Basic statistics for quality control in the clinical laboratory.

A systematic approach toward selection and evaluation of laboratory methods should improve the quality of the analytical service. However, any testing approach only assesses whether the analytical method can achieve the desired level of performance under the test conditions. It does not assure that the performance is actually achieved under the conditions of each routine analytical run. The quality of the routine analysis must be monitored by suitable quality control procedures. Unfortunately, the present practice of quality control achieves an arbitrary and usually unknown level of quality. Achieving a known level of quality requires that one understand the performance characteristics of the quality control procedures themselves. Achieving a specified level of quality requires that one design the quality control system to achieve a stated error specification. This can be accomplished by careful choice of control procedures in order to have the desired capability for detecting analytical errors which would invalidate the medical usefulness of the test results. A high-caliber quality control system will be the result of a logical sequence of the objective evaluation and selection of an optimal analytical method followed by regular rigorous statistical monitoring of each analytical method.

Analysis of Variance↗
PubMed1981

Selection of patients with chronic obstructive pulmonary disease for long-term oxygen therapy.

The Nocturnal Oxygen Therapy Trial, a study of oxygen therapy in patients with chronic obstructive pulmonary disease, has combined the experience of six centers concerning the selection of patients for oxygen treatment. Forty-five percent of hypoxic patients initially selected for the study improved enough during the one month of outpatient observation to allow suspension of plans to treat them with oxygen. Therefore, long-term oxygen therapy plans should only be made without a month of careful observation. Resting PaO2 values less than 40 mm Hg suggest instability or that chronic obstructive pulmonary disease is not the only cause of the hypoxemia. Nasal prong oxygen flow of 1 to 3 L/min reversed hypoxemia in 95% of stable patients with chronic obstructive pulmonary disease.

Clinical Trials as Topic↗
PubMed1981

Cerebrospinal fluid antibodies to neuronal cells: association with neuropsychiatric manifestations of systemic lupus erythematosus.

The validity of the hypothesis that some of the neuropsychiatric manifestations of systemic lupus erythematosus (SLE) are mediated by the direct effects of antibody binding to neuronal cell membranes is dependent on the demonstration of antineuronal activity within the central nervous system of patients with active central nervous system disease. Using a radiolabelled staphylococcal protein A assay, we tested cerebrospinal fluid from 27 patients with SLE and central nervous system manifestations, and cerebrospinal fluid from 18 additional patients with SLE but free of central nervous system disease for antibody reactive with the cultured human neuronal cell line SK-N-SH. Cerebrospinal fluid from 20 of 27 patients with active lupus central nervous system disease had increased immunoglobulin G (IgG) antineuronal activity compared with cerebrospinal fluid from two of 18 patients with SLE without central nervous system disease. Ninety percent of the patients with psychosis, organic brain syndrome or generalized seizures had increased IgG antineuronal activity as compared with only 25 percent of the patients who presented with hemiparesis or with chorea/hemiballismus. Antineuronal activity per microgram of IgG was concentrated eightfold in the cerebrospinal fluid of patients with active central nervous system disease as compared with the serum activity. Patients with or without active central nervous system disease did not differ significantly in the amount of serum antineuronal binding activity. The results are consistent with the hypothesis that the more diffuse central nervous system manifestations of SLE are a direct result of the interaction of antibody with neuronal cell membranes.

Antibodies↗
PubMed1981

Comparison of methods for estimating digoxin dosing regimens.

Five methods of predicting serum digoxin concentrations (SDCs), used in conjunction with three equations for estimating creatinine clearance, were compared. Radioimmunoassay was used to determine the nadir SDCs in 79 patients (38 men, 41 women) meeting predetermined study criteria. All patients, whose ages ranged from 33 to 94 years, had steady-state digoxin levels, were on oral digoxin, and were free from thyroid dysfunction, malabsorption syndromes, dehydration, and renal failure. Three equations, involving combinations of age, lean body weight, and serum creatinine, were used to estimate creatinine clearance (Clcr). These Clcr values were then used in each of five equations to estimate SDCs. The estimated SDCs were compared to actual SDCs in the 79 patients, and the effects of changing the fraction of dose absorbed and the method of determining Clcr were analyzed. No substantial difference in predictive reliability was evident among the methods studied. Poor correlations existed between observed and calculated SDCs (r less than 0.70), and these correlations were not significantly affected by gender, fraction of dose absorbed, or method of Clcr estimation. Higher correlations were found for the oldest and youngest age groups. Severe limitations are associated with the use of the formulas studied.

Adult↗
PubMed1980

Oral contraceptives and physiological variables.

Physiological variables were compared among women who had never used oral contraceptives, past users, and current users. Randomly selected subjects were aged 30 to 59 years. Blood was sampled for determination of blood glucose, serum cholesterol and triglyceride, and plasma insulin concentration. Summed postchallenge glucose and insulin values were used in analyses to represent the magnitude of response. Contours of glucose and insulin curves were represented by single numerical variables termed "G-CON" and "I-CON." Current users of oral contraceptives had significantly higher values of G-CON, I-CON, triglyceride, and systolic blood pressure than women who never used oral comtraceptives. Current users also had significantly higher levels of summed glucose, G-CON, and I-CON than former users. Use of currently prescribed oral contraceptives is associated with adverse physiological changes that are reversible after discontinuing such use.

Adult↗
PubMed1980

Intraoperative esophageal manometry: is it valid?

Forty-five patients undergoing a Collis-Nissen antireflux operation had preoperative, several intraoperative, and postoperative distal esophageal high-pressure-zone (HPZ) measurements. In 11 patients (24%), intraoperative manipulation of the esophagus alone, prior to beginning the repair, had a major effect upon the HPZ. The final mean intraoperative HPZ pressure (21.2 mm Hg) differed significantly (p less than 0.01) from that obtained postoperatively at 1 to 3 weeks (15.2 mm Hg), 6 months (11.2 mm Hg), and 12 mm Hg), and 12 months, (12.1 mm Hg). However, there was no significant statistical correlation between the final intraoperative HPZ pressures and those obtained after 6 and 12 months. Irrespective of the final intraoperative HPZ value, no patient undergoing acid reflux testing at 6 to 12 months after operation had any gastroesophageal reflux. It is concluded that esophageal manipulation (mobilization or dilation) results in variable intraoperative Hpz values that are not reliable predictors of HPZ values obtained late postoperatively. The rationale for altering the technique of an operation simply to obtain an "ideal" intraoperative HPZ value must be seriously questioned.

Female↗
PubMed1980

Physiological variables and diabetic status. Findings in Tecumseh, Mich.

A random sample of 568 participants in the Tecumseh, Mich, study, aged 30 to 59 years, was stratified according to blood glucose concentration to select a high proportion of diabetics. Subjects were categorized as overt diabetics, chemical or probable diabetics, or nondiabetics. Diabetic groups and nondiabetics were compared for levels of blood glucose, plasma insulin, serum cholesterol, serum triglyceride, blood pressure, and contours of glucose and insulin curves. Overt diabetics had high mean fasting blood glucose levels. Challenged diabetics had significantly higher concentrations of all variables except cholesterol than nondiabetics, even after adjustment for age and adiposity. Glucose intolerance, adiposity, and sex influenced variables independently. Risk of atherosclerosis is partly attributable to persistent hyperglycemia and related metabolic abnormalities in overt diabetics. Postchallenge diabetics have subtle hyperglycemia but a high frequency of other risk factors. Recent developments suggest that control of blood glucose may become feasible and useful in the prevention of cardiovascular disease in overt and challenged diabetics.

Adult↗
PubMed1980

Reproducibility of syphilis serology results.

In order to evaluate the stability and reproducibility of syphilis serology qualitative results, the results reported on replicate specimens in the College of American Pathologists Quality Evaluation Program during 1978 were examined. There is evidence of good stability of syphilis serology specimens and reproducibility of qualitative results separated in time by as much as nine months for specimens that are nonreactive or highly reactive. However, there is evidence of lack of such stability and reproducibility of weakly reactive specimens. There is no striking difference in these results for the RPR card or VDRL test. The FTA-ABS test is more stable over time. There is some indication that the lack of stability and reproducibility of weakly reactive specimens is primarily a function of the stability of the specimen, with laboratory performance playing a secondary role.

Pathology, Clinical↗
PubMed1980

The distribution of selected hematology measurements in the CAP survey.

Investigation of the 1978 CAP Hematology Survey results for hemoglobin, hematocrit, erythrocyte count, leukocyte count, prothrombin time, and partial thromboplastin time with respect to the assumption of normality and the method for detecting outliers was performed. The findings indicate that the assumption of normality, while not exactly valid, is reasonable for the purposes of the Survey, but that the method of determining outliers may be too stringent in the case of hemoglobin, hematocrit, erythrocyte count, and leukocyte count, and not appropriate for prothrombin time and partial thromboplastin time. These findings are similar to those reported earlier for selected chemistry and immunology constituents in the CAP Survey.

Erythrocyte Count↗
PubMed1979

Immunofluorescence studies of anti-T cell antibodies and T cells in systemic lupus erythematosus. Selective loss of brightly staining T cells in active disease.

Peripheral blood T cells from patients with systemic lupus erythematosus (SLE) and age- and sex-matched controls were studied by flow microfluorometry by using SLE anti-cell antibodies and fluorescein conjugated antibody to human IgM. Brightly staining cells were reduced in a number of patients with active SLE. Analysis of SLE T cells separated on a discontinuous stractin gradient indicated a preferential loss of cells, especially brightly staining cells, from one fraction. Quantitation of this phenomenon indicated that an average of greater than 90% of the brightly staining T cells from that fraction was lost in active SLE. This preferential loss of a subpopulation of T cells in patients with active SLE may be responsible for many of their immunologic abnormalities.

Antilymphocyte Serum↗