Heterophile antibodies rarely influence the measurement of thyroglobulin and thyroglobulin antibodies in differentiated thyroid cancer patients.

The aim of the study was to determine the impact of heterophile antibodies on the measurement of serum thyroglobulin (Tg), thyroglobulin recovery, and thyroglobulin antibody levels in differentiated thyroid carcinoma patients. We studied serum samples of 201 individual patients that were followed in our hospital for differentiated thyroid carcinoma and 52 control samples. Samples were split; half were treated by incubating the sample for 1 h in HAB-blocking tubes, the remainder was left untreated. Subsequently thyroglobulin and thyroglobulin antibody levels were measured in both the blocked and untreated samples. A difference between the two samples was considered significant if the blocked sample deviated from the untreated one by more than 2.77 times the standard deviation for the method. In the measurement of Tg, 2 patients showed a moderate, but significant lowering of Tg levels after blocking treatment, but not so great as to affect clinical management. None of the 52 controls showed heterophile antibody interference in thyroglobulin measurement. Neither in DTC patients, nor in controls was any possible heterophile antibody interference encountered. And in all thyroid carcinoma patients, and in all but one controls, no interference was found in the thyroglobulin antibody measurement. All in all a possible heterophile antibody interference was found in 3/759 tests (0.4%). We can assume that heterophile antibody interference is not a factor to be reckoned with in the daily practice of Tg measurement in the treatment and follow-up of differentiated thyroid carcinoma patients.