Methodological evaluation of a new chemiluminescence immunoassay for thyrotropin using acridinium ester-labelled...

A recently available immunochemiluminometric assay (ICMA) for TSH developed by Ciba Corning Corp. has been evaluated. This system (Magic Lite) uses an acridinium-ester-labelled antibody and magnetizable particle for bound-free separation. In each assay only two calibrators are carried out and used to re-scale a manufacturer-generated curve stored in the memory of the luminometer. The precision of the response (RLU) estimated by all duplicates of 14 runs was about 4% for responses greater than 12,000 RLU (corresponding to a concentration interval 0.7-113 microIU/ml) and worsened in the lower range (up to 10% CV); the sensitivity, computed from the mean within-assay precision profile, was 0.028 microIU/ml; the between-assay precision ranged from 4.6 to 13.1 CV%. Regression analysis of ICMA results (y) against consensus values of Behring IRMA (x) on 15 QC sera assayed in an inter-laboratory survey (concentration range 1-30 microIU/ml) gave y = -0.003 + 0.98x indicating a good agreement of the two techniques. Similar conclusions have been derived from the comparison of the ICMA results (y) in the low TSH concentration range (less than 1 microIU/ml) against the IRMA Boots Celltech (x) on 80 patient samples (y = 0.04 + 1.04x).