PERMANENT PROGRAM OF QUALITY ASSURANCE OF THE MNIH .1. THE 1ST PHASE OF THE PROGRAM

Background information. This is the report of the first phase of an in ternal/external permanent program of the MNIH (Mexican National Instit utes of Health). The permanent program evolved from a previous one ope rating from 1984 to 1988 in the MNIH (Refs 1-5). Objective. To evaluat e the precision of the assay systems used currently by the clinical ch emistry laboratories of the MNIH. Material and methods. A single batch of a lyophylized control serum prepared for the program by an agency of the Ministry of Health was used throughout the study. During a peri od of four months, the participants were provided with flasks of the c ontrol serum every two weeks to assay the analytes included in the rou tine daily work of each laboratory. They also received every two weeks an update of the mean of means and interlab CV of the information ava ilable. Results. The 11 participants reported 6278 results of 24 analy tes (6 enzymes, 8 electrolytes and 10 organic metabolites) assayed in 179 systems. The majority of the systems (162/179 = 91%) were autoanal yzers. There were 168 systems which could be evaluated in precision an d 115 in accuracy. The rate of imprecision was 15% (25/168) and of ina ccuracy 17% (19/115). Conclusions. 1. The participants were able to ac t as a reference group to assign the value of 12 analytes in a control serum with low concentration of most analytes. 2. Imprecision was con centrated in two participants (Labs B and J with 15 of the 25 imprecis ions : see table 2). The second phase of the program will be to identi fy and if possible eliminate the sources of variation in the systems o f participants B and J.