Biomedical subjects

D Twedt

Publications and source records attributed to D Twedt.

7 recordsLinked to original sources

PubMed1996

Diurnal change of blood count analytes in normal subjects.

Short-term, within one 24-hour day (diurnal period) within-person changes of the principal blood count analytes in healthy subjects were studied at three major institutions. The results from each test site were indistinguishable and were therefore combined to make a database of 96 healthy subjects. Analytical imprecision of each analyte was subtracted from the total observed variation to give true diurnal change. Each analyte showed characteristic changes. As would be expected, cellular properties of erythrocytes, such as MCV (mean cell volume) and MCH (mean cell hemoglobin) showed negligible change. The red cell count, hematocrit, and hemoglobin showed changes that were consistent with fluid balance change. Total white cell count and some differential count components showed major changes that raised questions of the confidence limits of clinical decision levels and the validity of commonly used reference intervals. Platelet count changes were typically less than analytic imprecision, suggesting the need for improvement in this aspect of analyzer performance.

Blood Cell Count↗

PubMed1995

Absolute versus proportional differential leucocyte counts.

Comparison of absolute (cells x 10(9)/l) leucocyte differential counts with proportional (percentage) counts from the same stained films demonstrates significant disparities between these two methods of reporting results. Within reference intervals the disparities are modest but become significant in specimens with distributional abnormalities. Although neither method of reporting is formally espoused in this communication, it is suggested that use of the absolute count is more likely to provide diagnostic support.

Diagnostic Errors↗

PubMed1994

Oxidant injury to hepatic mitochondria in patients with Wilson's disease and Bedlington terriers with copper toxicosis.

BACKGROUND/AIMS: Copper overload leads to liver injury in humans with Wilson's disease and in Bedlington terriers with copper toxicosis; however, the mechanisms of liver injury are poorly understood. This study was undertaken to determine if oxidant (free radical) damage to hepatic mitochondria is involved in naturally occurring copper toxicosis. METHODS: Fresh liver samples were obtained at the time of liver transplantation from 3 patients with Wilson's disease, 8 with cholestatic liver disease, and 5 with noncholestatic liver disease and from 8 control livers. Fresh liver was also obtained by open liver biopsy from 4 copper-overloaded and 4 normal Bedlington terriers and from 8 control dogs. Hepatic mitochondria and microsomes (humans only) were isolated, and lipid peroxidation was measured by lipid-conjugated dienes and thiobarbituric acid-reacting substances. In humans, liver alpha-tocopherol content was measured. RESULTS: Lipid peroxidation and copper content were significantly increased (P < 0.05) in mitochondria from patients with Wilson's disease and copper-overloaded Bedlington terriers. More modest increases in lipid peroxidation were present in microsomes from patients with Wilson's disease. Mitochondrial copper concentrations correlated strongly with the severity of mitochondrial lipid peroxidation. Hepatic alpha-tocopherol content was decreased significantly in Wilson's disease liver. CONCLUSIONS: These data suggest that the hepatic mitochondrion is an important target in hepatic copper toxicity and that oxidant damage to the liver may be involved in the pathogenesis of copper-induced injury.

Adolescent↗

PubMed1992

A method for the independent assessment of the accuracy of hematology whole-blood calibrators.

An independent assessment of the accuracy with which a large manufacturer assigned values to hematologic calibrators was performed. Data were collected from 1,767 hospitals and clinics distributed over North America. Statistical analysis of the mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration of these patient data confirmed the accuracy of the values for hemoglobin, erythrocyte count, hematocrit, and erythrocyte indices for the calibrators manufactured and released during a 9-month period. This approach proved both workable and effective in detecting inaccuracies of less than 1%. Few technologist-users have the time or the equipment to verify independently the accuracy of hematologic calibrators. The manufacturers should perform ongoing, independent assessments of the accuracy of their products. The statistical analysis of patient data provides manufacturers with a suitable method.

Calibration↗

PubMed1988

Hepatozoon sp. in wild carnivores in Texas.

Twelve coyotes (Canis latrans), three bobcats (Lynx rufus) and six ocelots (Felis pardalis) from the Gulf Coast of Texas were infected with Hepatozoon sp. The geographic distribution of infected wild animals coincides with the highest prevalence of Hepatozoon canis infection in domestic dogs for which the wild species may act as a reservoir.

Animals↗

PubMed1985

The Coulter Counter leukocyte differential.

The leukocyte differential counting capability of the Coulter Counter model S-PLUS IV was evaluated for precision, accuracy, and clinical sensitivity. The evaluation used procedures described in the NCCLS tentative standard (H20-T) when these were appropriate for this technology. Within its inherent constraints, the system was found to be more reproducible than the stained-film reference method and at least as accurate. Clinical sensitivity was equivalent to that of a four-slide, microscope differential count. Reference ranges for the cell classes identified by the instrument were similar to those given by the stained-film method.

Biometry↗

PubMedDate not supplied

Continuum analysis method applied to blood count reference intervals.

Conventional methods for extracting reference values from a sample of a purported normal population have a tendency to include some paranormal individuals and to obscure the existence of marginal or subclinical disorders. The suggestion is offered of defining the normal range of an analyte by extrapolation of the portion of its dispersion that fits a continuum. The method softens the present dichotomous character of the reference range. It narrows the normal range of some hematology parameters, suggesting that some paranormal individuals are excluded.

Adolescent↗