CLINICIANS DILEMMA: FALSELY UNDETECTED TSH LEVELS DUE TO TSH ISOFORM ON POPULAR COMMERCIAL IMMUNOASSAY IN INDIAN SUBJECT AND RETROSPECTIVE ANALYSIS

Introduction: TSH is one of the most routinely measured tests the clinical laboratory to diagnose and monitor thyroid diseases. TSH as the preferred screening test as recommended by The American Thyroid Association and the American Association of Clinical Endocrinologists for diagnosing thyroid dysfunction. Third-generation Ultra serum TSH assays have a functional sensitivity of 0.001 uIU/mL and have been considered highest among biochemical assay for assessing thyroid disorders. However, as observed in many clinical laboratories sometimes results of TSH assays are discordant among different immunoassay platforms. Case Report: TSH values of a 56 years old male on Siemens Attelica while TSH was found to be elevated on Abbott Architect 1000 and Beckman Coulter DXI800. Retrospective analysis revealed few other cases (8/190) approx. 4.2 % showed discordant TSH values. This was found to be possibly because of mutation in TSH beta region (R55G). Conclusion: Our present study suggest that these individuals who shows <0.001 values on Siemens Attelica must be tested with other platforms to assure appropriate management of disease. Further, clinicians and laboratory staff need to be aware about TSH variants along with other reported interferences.