A new luminescence immunoassay for thyrotropin using coated tubes: evaluation and comparison with immunoradiometric...

A recently available chemiluminescence immunoassay (LIA-MAT) for TSH, set up by Byk-Sangtec Diagnostica, has been evaluated and compared with IRMA methods. The system LIA-MAT uses two monoclonal antibodies: one coated on tubes and the other labelled with isoluminol. To compute the within-assay precision profile, we estimated the response error relationship from all the duplicates (420) of eleven experiments. The CV of the response was 4-5% from the maximal response until 10,000 RLU (corresponding to about 1 microIU/ml); in the lower response range the CV worsened up to 8%. The sensitivity, derived from the precision profile, was 0.052 microIU/ml similar to that found in IRMA-MAT (0.044 microIU/ml); the working range extended from 0.33 to 100 microIU/ml. Results from LIA-MAT in the concentration range 1-30 microIU/ml were compared with the consensus mean produced by users of IRMA methods (IRMA-MAT, IRMA-Behring, Maiaclone Serono) participating in an inter-laboratory survey; a good correlation with IRMA techniques was found. The distribution of TSH determinations produced by LIA-MAT on 62 low concentration sample (less than 0.3 microIU/ml) from patients unresponsive to TRH test, was found similar to that observed for the kit IRMA Boots-Celltech assumed as reference.