Influence of specimen carryover on sensitive thyrotropin (TSH) assays: is there a problem?
A relatively slow transition has occurred from so-called 1st-generation thyrotropin (TSH) assays (e.g., RIAs) through 2nd-generation assays (e.g., IRMAs) to 3rd-generation assays (e.g., immunochemiluminometric assays). Analysis of data from a modified internal quality-control design, followed up by a computer simulation, showed that specimen carryover has minimal effect on 2nd-generation TSH assays. However, extension of the simulation to a 3rd-generation assay showed the possibility of substantial effects in the subnormal region. Carryover of 1:1250 (0.08%), for example, may reduce the theoretical 10-fold precision improvement claimed for 3rd-generation assays to nearer fourfold. Simulation results suggest maximum allowable specimen carryover of approximately 1:10,000 (approximately 0.01%) for 3rd-generation TSH assays. We suggest that when automated specimen handling is used in a TSH assay, a well-designed carryover experiment should become a routine part of reports that claim 3rd-generation (or better) performance characteristics.
Sadler
W A
WA
Department of Nuclear Medicine, Christchurch Hospital, New Zealand.
Murray
L M
LM
Turner
J G
JG
D001322:Autoanalysis; D003198:Computer Simulation; D006801:Humans; D007118:Immunoassay / Q000706:statistics & numerical data*; D015592:Immunoradiometric Assay / Q000706:statistics & numerical data; D008163:Luminescent Measurements; D011786:Quality Control; D011863:Radioimmunoassay / Q000706:statistics & numerical data; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013972:Thyrotropin / Q000097:blood*
D013972:Thyrotropin