COMPARISON OF KODAK AMERLITE FT4 AND TSH-30 WITH T-4 AND TSH AS FIRST-LINE THYROID-FUNCTION TESTS

Objectives: To evaluate the effect of test automation and a change in strategy for thyroid function tests (TFT) on personnel needs and turn- around time. The first-line TFT were changed from T-4 and TSH to FT4 a nd TSH-30. Design and Methods: Samples received for TFT from 357 rando mly selected patients were analyzed by RIA for T-4, and by IRMA for TS H as first-line tests. FT3 and TBG were requested as back-up tests whe n indicated. Patients were classified on the basis of these results an d the clinical information received. All the samples were reanalyzed f or FT4 and TSH on the Amerlite Processing Center, which is a batch, se miautomated immunoassay system. The thyroid status of the patients was compared using the two protocols and available clinical data. Results : There was good correlation between TSH-IRMA and TSH-30 in the 160 pa tients classified as euthyroid (r = 0.956; p < 0.001) and no euthyroid patient was reclassified with the new strategy. In 21 patients with b orderline raised TSH-IRMA, FT4 was found to be low in only 2. All If p atients classified as hypothyroid had TSH results greater than 10 mU/L and all except 2 patients had FT4 less than 11 nmol/L. The status of 21 hyperthyroid as well as 40 patients on carbimazole could be determi ned biochemically on the basis of agreement between both the FT4 and T SH-30 results. FT3 was only required if the FT4 and TSH-30 results wer e not in agreement. In 42 patients on T-4 therapy, adequacy of replace ment was assessed better using FT4 and TSH-30. No patient required bac kup testing with TBG to determine thyroid status using the new testing protocol. The change in TFT protocol reduced the 95% turn-around time from 3 days to 1 day. Conclusion: The introduction of FT4 and TSH-30 as first-line TFT improved the turn-around time for TFT, resulted in 2 5% reduction in personnel requirements, 60% reduction in FT3 assays, a nd discontinuation of TBG assay.