Qualitative evaluation of in-house immunoassays of T3 and T4 and TSH based on bulk reagents

Increase in cost of RIA (radioimmunoassay) kit assays has led to our attempts to seek cheaper alternates. Assays based on bulk reagents were started in 1988. Statistical and quality control data on 50,51 and 52 assay batches of T3,T4 and TSH respectively has been collected from the beginning. Cumulative assay parameters show that T3 and T4 assays are almost equally precise. TSH assay is most imprecise in the group especially at low concentration levels. The working ranges of T3 and T4 assays defined at 10% error limit are quite wide and cover low, medium and high levels of hormones. In TSH the assay working range does not cover levels below 10 micro lU/ml. The variability of curve parameters is similar in this group of assays. Quality control results are most reproducible in T4 assays with a batch variability of 11.9% T3 and TSH assay results are equally reproducible. Overall within assay drift is low in all assays. IQC charts of these assays show occasional significant positive or negative shift of results from mean which might be related to methodological variations of quality among various distributions of reagents. The reproducibility and precision of results could be further improved by harmonizing distributions of reagents. (author)