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D Hasler

Publications and source records attributed to D Hasler.

3 recordsLinked to original sources

Evaluation of automatic and semiautomatic coagulation assay instruments.

The precision of five instruments (Coag-A-Mate, Auto-Fi, Coagulyzer, Electra 600 and Fibrometer) in performing activated partial thrmboplastin time (PTT) assays were compared using three different coagulation reagent systems (Ortho, Dade, and General Diagnostics) utilizing normal and abnormal control reagents. There were wide variations in mean PTT values and co-efficient of variation (CV) among all instruments and for each instrument utilizing different reagents. The smallest CV was noted for The Coagulyzer using Dade reagents, the Coag-A-Mate using Dade and General Diagnostic reagents and the Auto-Fi using General Diagnostic reagents. Auto-Fi values were always longer than those determined with the Fibrometer whereas the optical detection instruments usually gave shorter values. The range of normal values for the prothrombin time (PT) and PTT assay was recorded simultaneously on blood samples of 52 healthy donors utilizing the Coagulyzer with Ortho reagents, the Coag-A-Mate with General Diagnostic reagents nd the Auto-Fi with Dade reagents. No differences were noted between male and female donors. There was a poor correlation among PT results recorded by all instruments. For the PTT assay, results obtained with the Coag-A-Mate and the Auto-Fi had a correlation of 0.84. The normal mean plus 2 or 3 standard deviations determined by the Auto-Fi and the Coag-A-Mate were used to classify blood samples from 263 patients as normal or abnormal when assayed by each instrument. For the PTT assay, coincidence was attained in 91.2% of the samples and discrepancies (a blood classified abnormal by one instrument and normal by the other) were evenly distributed for both instruments. For the PT assay, coincidence occurred in 85.1% of the cases and there was a statistically significant trend (P < 0.05) for the Auto-Fi in classifying abnormal samples categorized normal by the Coag-A-Mate.

Automation

Effects of time, platelet concentration, and sex on the human platelet aggregation response.

The platelet aggregation responses induced by adenosine diphosphate (ADP) and collagen were characterized by parameters defining rate and extent of reaction. Values were compared on the basis of platelet concentration, time elapsed between sample collection and test performance, and sex of donors. Rate and extent of aggregation varied as a function of platelet concentration. Maximal responses were obtained for platelet concentrations greater than 100,000/microliter. Results from samples processed after 90 min of incubation at room temperature were consistently and significantly lower than those obtained from samples processed immediately. ADP-induced aggregation responses elicited by samples from male and female normal donors differed significantly. This indicates that comparisons between normal and patient results should be made with sex-matched individuals to avoid erroneous interpretations.

Adenosine Diphosphate