ABSTRACT
@#This study aims to determine the diagnostic value of a 99mTc-pertechnetate (99m TcO-4) thyroid scan among patients with DTC who underwent thyroidectomy to assess functioning thyroid remnants before radioactive iodine therapy. A retrospective non-experimental cross-sectional design was done to compare the results of the 99m TcO-4 thyroid scan with the patient's post-RAI scan. A review of all our patients' charts was done for eight years, and after excluding those that did not fit the criteria, 70 patients were included in the study. Data collected was analyzed on a "per patient" basis– where patients either had a "positive scan" or "negative scan", and on a "per lesion" basis – where every lesion's presence and size were compared on both modalities. 99m TcO-4 thyroid scan in the "per patient" analysis showed a sensitivity of 73.91%, specificity of 100%, positive predictive value (PPV) or 100%, and accuracy of 74.29%, however, negative predictive value was determined to be 5.26%. In the "per lesion" analysis, the scan had a less favorable performance with the computed sensitivity of 61.69%, PPV of 94.93%, and accuracy at 59.41%. It was then concluded that 99mTc-pertechnetate scan may be useful in determining functioning remnant thyroid tissue and subsequent management of DTC patients after thyroidectomy, but must take note of its low negative predictive value.
Subject(s)
Thyroid NeoplasmsABSTRACT
99mTc-pertechnetate for thyroid function studies is given oral, need not be sterile or pyrogen-free. The patients need be fasting only 3 hours and no food should be ingested for at least two hours following the oral administrations. The optimum time for uptake measurement is 2 hours after dose. The euthyroid range is from 2.5-11.2%. The suppression test can be carried out with 60 microgram of T3 daily for 5 days. A normal uptake response to T3 is a suppression to < 80% of initial uptake. Poor suppression is characteristic of grave’s disease. The comparison between 99mTc-uptake and RIA, serum T4 and T3 in 50 patients results in similar findings in both euthyroidism and hyperthyroidism, except for one subject with heart disease. The uptake and suppression test can give more information about iodine deficiency goiter. Using 131I and 99mTcO4, we compared 240–iodine uptake and 20-technetium uptake in the same subjects. The diagnosis of 33 patients was made on clinical grounds and confirmed by RIA-technique. The indications were the same, but the iodine uptake was more sensitive, for 6 patients with iodine deficiency disease whereas technetium found only 3. The suppression studies, 131I is satisfied in all cases. Technetium is reasonable in hyperthyroidism and iodine deficiency goiter. If 20-uptake is in normal range, some of them are a suppression and some fail to suppress. Because the normal rang of technetium is lower than iodine and the thigh correction for extrathyroid activity is inadequate. In patients with low 99mTc-uptake, the suppression test is not needed neither are there cases of thyrotoxicosis with false low 99mTc-uptake such might occur with early iodine avidity and wash out at 24 hours.