AIM: The aim of this study was to establish normal reference values for 99mTc-pertechnetate thyroid uptake in the local patient population.
To our knowledge, there have been no published reports on normal reference values for the Australian population. The current normal reference values for thyroid uptake used at our institution of 1 – 4% are based on data from a study performed in 1971. Uptake values may change with geographical location and from one decade to the next with studies from Namibia, Brazil and the United Kingdom establishing updated normal reference values for local populations of 0.15 – 1.69%, 0.4 – 1.7%, and 0.2 – 2.0% respectively.
METHODS: A prospective study was conducted alongside a retrospective audit for 271 patients undergoing parathyroid scans in our Nuclear Medicine department between January 2017 and December 2021. Anterior thyroid static images acquired following intravenous injection of 99mTc-pertechnetate were reviewed to calculate thyroid uptake. Patients with known and / or prior thyroid conditions, abnormal biochemical thyroid function tests and / or abnormal appearances on 99mTc-pertechnetate thyroid scans were excluded from the study.
RESULTS: Of the 271 patients a total of 151 studies met the eligibility criteria and were included for analysis. The median uptake value in our patient population was 0.97% with a 95% reference range of 0.4 – 2.4%.
CONCLUSION: The calculated normal reference range in this study was found to be considerably different to that of the 1971 study findings of 1 – 4 %. The results demonstrate the importance of periodic evaluation of normal uptake values for geographically varied populations. Based on this finding we recommend updating the normal range for 99mTc-pertechnetate thyroid uptake to reflect values relevant to the local population.