A Case With Immunoassay Interferences in the Measurement of Multiple Hormones

Commonly used immunoassays are not free from interference, which can be a confounder in the interpretation of test results. We present a case with extremely high multiple hormone levels due to such interference.

A 33-year-old woman with no specific symptoms had markedly elevated TSH with normal free T4 and free T3 levels. Repeated measurements revealed discordantly high TSH, ACTH, FSH, PTH, IGF-1, prolactin, β-human chorionic gonadotropin, and calcitonin levels without the associated clinical pictures. The measurements were repeated with the same patient sample on four different analytical platforms using chemiluminescence immunoassays/electrochemiluminescence immunoassays, and the results were divergent on each platform. Serial dilutions of serum samples revealed nonlinearity, suggesting assay interference. All hormonal measurements were in the normal range when heterophile antibody blocking tubes were used. The serum of the patient was then subjected to polyethylene glycol precipitation. The post-polyethylene glycol recovery resulted in hormone levels in the normal range. The patient did not receive any medications and has been under follow-up without any signs and symptoms for 24 months.

This report illustrates a rare case of falsely elevated hormone levels due to assay interference caused by heterophile antibodies. We point out the importance of a close collaboration between clinicians and the laboratory to avoid unnecessary clinical investigations as well as inappropriate treatments.