INTER-LABORATORY DIFFERENCE AMONG 11 CLINICAL LABORATORIES IN THE OKAYAMA CITY AREA

The aim of the present study was to find the cause of inter-laboratory differences in laboratory test data and to examine whether control as sessment helps to reduce inter-laboratory differences. Blood and serum samples of one healthy subject and one subject with liver cirrhosis w ere analyzed by 11 laboratories in the Okayama City area. No differenc es were found in the assay units of 26 tests surveyed. However, consid erable differences were observed in test data, reference interval, and clinical level (CL), though most laboratories pointed out that the te st data for the normal subject was within the reference intervals and those for the patient with liver cirrhosis showed abnormalities in tes ts for liver function. The difference in reference intervals was serio us in the tests of direct bilirubin (D-Bil), thymol turbidity test(TTT ), alkaline phosphatase (ALP), gamma-glutamyltranspeptidase (GGTP) and choline sterase. Marked differences in CLs were found in the tests of D-Bil, TTT, ALP, GGTP, creatine phosphokinase, amylase, heavy density lipoprotein cholesterol and white blood cell count. However, three he patologists independently suggested that such inter-laboratory differe nces would not seriously affect a clinical decision on the disease sta tus of the cirrhotic patient. Most tests that showed a trend error in a recent quality control survey appeared to have the same trend in the present study. These results indicate that inter-laboratory differenc es occur at various levels and control assessment are helpful in estab lishing, and therefore reducing, the level of inter-laboratory differe nces.