A comparative study of five commercial reagents for the Coulter Model S: a proposed method for reagent evaluation.

A comparative study of five competitive commercial reagents for the Coulter Model S was performed jointly by two large, busy hospital laboratories with active quality control programs. Both laboratories, independently using the same reagent systems, studied 20 consecutive blood samples from patients from their own respective hospital for 20 days. Data from both laboratories were analyzed by standard and nonstandard statistical methods, and the results from both laboratories were compared. Although all reagent systems performed reasonably well in a clinical setting, highly significant statistical differences in their precisions were demonstrated by using univariate and multivariate techniques. The statistical method developed in this study can be applied to other systematic investigations that compare reagent systems.