TSH-Assay Interference: Still with us

Measurement of thyroid stimulating hormone (TSH) concentration is the first line test for the assessment of thyroid function. However, interference may lead to falsely elevated TSH concentrations, unnecessary investigations, and eventually misdiagnosis. Our case report describes interference by heterophilic antibodies on an automated TSH assay leading to false positive results. Such interference was however not observed with another automated platform. The assay format, the antibodies used, and the volumes required for the analysis may influence the results and the sensitivity to interferences. It is therefore important to detect and report these interferences to stimulate the continuing improvement of immunoassays. Furthermore, the effective tracking of interferences with immunoassays is dependent on multidisciplinary collaboration and requires continuing cross-talk between physicians and laboratory staff. (Clin. Lab. 2012;58:1305-1307. DOI: 10.7754/Clin.Lab.2012.120201)