Comparative Study of Biological and Analytical Variability of Automated Clinical Chemistry Tests

Abstract

Background : Results of automated clinical chemistry tests are affected by many

factors including analytical variability. In 1976, the College of American Pathologists

(CAP) Conference on the analytical goals in clinical chemistry recommended that

analytical variability should be less than 1/4 of the appropriate biological variability to

improve distinction between normal and diseased populations, This study is conducted to

evaluate whether automated clinical chemistry analyses performed in our laboratory is in

conformance with the CAP's recommendation.

Methods : Routine chemistry and electrolyte tests were performed using Hitachi 747

automatic analyzer on 22 healthy volunteers Blood samples were obtained from the

volunteers' same vein twice in one week interval to stuffy the total variability Serum

samples from 12 subjects were tested in duplicate immediately after blood collection for

within-run analytical variability, and samples from another 10 subjects were repeated

after 6 hours for within-day analytical variability. Within-run analytical variability plus

within-day analytical variability make total analytical variability. Biological variability

was defined as the difference between total variability and the analytical variability

Finally, ratios of analytical and biological variabilities were calculated.

Results : The ratios of analytical and biological variabilities of uric acid, glucose, and

K were less than 025. But ratios of BUN, PO4, alkaline phosphatase, total

bilirubin, AST cholesterol, ALT, Cl, and protein exceeded 0.25 The ratios of Na, Ca,

albumin, CO2, and creatinine could not be calculated,

Conclusions : It is suggested that the analytical processes of the automated clinical

chemistry tests be improved so as to be in conformity with the CAP's recommendation.