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[Chemico-clinical permanent program of the NIH. I. The first phase of the program]
A Loría1, S Zaltzman, J M Cristerna
1Dpto de Control de Calidad, Instituto Nacional de Nutrición Salvador Zubirán.
Background Information:
This is the report of the first phase of an internal/external permanent program of the MNIH (Mexican National Institutes of Health). The permanent program evolved from a previous one operating from 1984 to 1988 in the MNIH (Refs 1-5).
Objective:
To evaluate the precision of the assay systems used currently by the clinical chemistry 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 period of four months, the participants were provided with flasks of the control serum every two weeks to assay the analytes included in the routine daily work of each laboratory. They also received every two weeks an update of the mean of means and interlab CV of the information available.
Results:
The 11 participants reported 6278 results of 24 analytes (6 enzymes, 8 electrolytes and 10 organic metabolites) assayed in 179 systems. The majority of the systems (162/179 = 91%) were autoanalyzers. There were 168 systems which could be evaluated in precision and 115 in accuracy. The rate of imprecision was 15% (25/168) and of inaccuracy 17% (19/115).
Conclusions:
1. The participants were able to act as a reference group to assign the value of 12 analytes in a control serum with low concentration of most analytes. 2. Imprecision was concentrated in two participants (Labs B and J with 15 of the 25 imprecisions: see table 2). The second phase of the program will be to identify and if possible eliminate the sources of variation in the systems of participants B and J.