Background: Serum thyrotropin (TSH) has been recommended for the initial assessment of patients with thyroid nodules to exclude functional thyroid nodules (FTN). However, the sensitivity of TSH is very low. The increased level of thyroid peroxidase antibody (TPOAb) is considered to be one of the reasons.
Objective: To investigate whether normalized TSH (nTSH) can improve diagnostic efficiency by removing TPOAb interference in the first evaluation of thyroid nodules compared with traditional TSH strategy.
Methods: Thyroid nodules were retrospectively analysed in 90 patients with FTN and 1038 patients with non-functioning thyroid nodules (non-FTN). The regression coefficient (β) of TPOAb affecting the TSH levels was assessed in patients with thyroid nodules, and then, the nTSH level was calculated based on the following formula: nTSH = TSH-β*TPOAb. We used nTSH levels to initially evaluate the thyroid nodules instead of the traditional TSH values and finally compared the results of the two strategies.
Results: The sensitivity, specificity, accuracy, positive prediction rate (PPV) and negative prediction rate (NPV) of nTSH for accessing FTN were 50.00%, 87.70%, 84.67%, 26.01% and 95.29%, respectively, which were better than the values of 48.90%, 78.70%, 76.33%, 16.60% and 94.67% associated with TSH, respectively (p < 0.001).
Conclusion: Serum TPOAb testing is recommended for the first assessment of thyroid nodules. Normalized TSH levels can improve assessment efficiency compared to traditional TSH assessment, increase the specificity and reduce an unnecessary 99mTc-TS test.
Keywords: Normalized TSH; TPOAb; diagnostic efficiency; improvement; initial assessment; interference; thyroid nodules.