AquaLite bioluminescence assay of thyrotropin in serum evaluated.

We studied a new commercially available thyrotropin (TSH) assay, the AquaLite Bioluminescence TSH-Immunoassay (SeaLite Inc.). This assay has a detection limit of 0.005 mIU/L and a functional sensitivity of 0.017 mIU/L and meets the requirements of a third-generation TSH assay. Using this assay, we measured serum TSH in 153 euthyroid individuals and in the following patients: 32 primary hypothyroids; 38 primary hyperthyroids; 35 with thyroid cancer receiving suppressive therapy with levothyroxine (L-T4); 33 receiving replacement L-T4 aimed at reaching and maintaining a euthyroid status; 23 with subclinical hyperthyroidism; and 52 hospitalized for nonthyroidal illnesses (NTI). The AquaLite TSH assay perfectly discriminated hypothyroid and untreated hyperthyroid patients from euthyroid subjects and clearly discriminated between overtly and mildly hyperthyroid patients. Intermethod comparisons showed that the AquaLite and the Nichols assays were more effective than the ACS-180 and the TOSOH assays in discriminating among hyperthyroid patients, including patients over-treated with L-T4.