Assessment of normal reference values for thyroid uptake of technetium-99m pertechnetate in a Saudi population.

Background: Thyrotoxicosis is a common medical problem. Thyroid nuclear imaging with either I or technetium-99m (Tc-99m) pertechnetate are used to determine the cause. Although I has been the standard technique, Tc-99m pertechnetate is now commonly used, acceptable and easier to perform. The commonly used normal value of Tc-99m pertechnetate is 1-4%, but lower normal values have been reported in different populations.

Objective: Determine normal reference range of Tc-99m pertechne-tate thyroid uptake for thyroid scintigraphy in Saudi Arabia.

Design: Retrospective, cross-sectional.

Setting: Nuclear medicine service at tertiary care center in Riyadh.

Patients And Methods: We used data from biochemically euthyroid patients who underwent a thyroid Tc-99m pertechnetate scan while having parathyroid scintigraphy for hyperparathyroidism between April 2009 to April 2019. Medical records and biochemical thyroid function tests were reviewed and Tc-99m pertechnetate thyroid uptake values were determined for each patient.

Main Outcome Measures: Thyroid uptake of Tc-99m pertechne-tate in euthyroid patients.

Sample Size: 167 RESULTS: The mean and median uptake of Tc-99m pertechnetate in euthyroid patients were 0.86% and 1.0%, respectively, and the inter-quartile range was 0.0-1.0%. The normal reference range in the study population was 0.2-2%. Thyroid uptake inversely correlated with age in females (r=-0.37, <.001), males (r=-0.46, =.001), and for all patients (r=?0.39, <.0001).

Conclusion: The range for normal thyroid Tc-99m pertechnetate was lower than the standard 1-4% range. Moreover, uptake decreased with age. Further studies are needed to establish the normal age-adjusted uptake for the thyroid Tc-99m pertechnetate scan.

Limitations: Single center and retrospective.

Conflict Of Interest: None.