Heterophilic antibody interference with TSH measurement on different immunoassay platforms

Interference due to the presence of heterophilic antibodies may lead to falsely low or high analyte concentrations, but falsely elevated values are more common in most immunoassay platforms. We report a case of a 53-y old female patient underwent radical thyroidectomy for thyroid papillary carcinoma and the results of TSH in the Siemens Advia Centaur XP after surgery were not suppressed, ranging from 5.73 and 6.61 μIU/ml.

The status of the thyroid was then assessed using 4 assay platforms from Siemens, Abbott, Roche and Beckman.

The results of TSH were 5.52, 0.54, 0.12, and <0.015 μIU/ml, respectively. After the samples were pretreated with the heterophilic antibody blocker, results given by Siemens, Abbott, and Roche showed significant decreases of 0.003, 0.001, and 0.005 μIU/ml, respectively. Therefore, it was confirmed that the presence of heterophilic antibodies in the patient samples interfered with the TSH measurements in multiple assay systems.

Clinicians must be aware of the possible assay interference, including the measurements of FT4, FT3 and TSH, results may be misleading in the presence of heterophilic antibodies, in particular when the results of thyroid function tests do not fit the patient clinical presentation.