Accuracy of increased thyroid activity during pertechnetate scintigraphy by subcutaneous injection for diagnosing hyperthyroidism in cats.
Our purpose was to determine the accuracy of increased thyroid activity for diagnosing hyperthyroidism in cats suspected of having that disease during pertechnetate scintigraphy using subcutaneous rather than intravenous radioisotope administration. Increased thyroid activity was determined by two methods: the thyroid:salivary ratio (T:S) and visual inspection. These assessments were made on the ventral scintigram of the head and neck. Scintigraphy was performed by injecting sodium pertechnetate (111 MBq, SQ) in the right-dorsal-lumbar region; static-acquisition images were obtained 20 min after injection. We used 49 cats; 34 (69%) had hyperthyroidism based on serum-chemistry analysis. Using a Wilcoxon's rank-sum test, a significant difference (P < 0.0001) was detected in the T:S between cats with and without hyperthyroidism. Using a decision criterion of 2.0 for the T:S, the test accurately predicted hyperthyroidism in 32/34 cats (sensitivity, 94%; 95% confidence interval (CI), 85-100%) and correctly predicted that hyperthyroidism was absent in 15/15 cats (specificity, 100%; CI, 97-100%). Using visual inspection, the test accurately predicted hyperthyroidism in 34/34 cats (sensitivity, 100%; CI, 99-100%) and correctly predicted that hyperthyroidism was absent in 12/15 cats (specificity, 80%; CI, 56-100%). The positive and negative predictive values were high for a wide range of prevalence of hyperthyroidism. And, the test had excellent agreement within and between examiners. Therefore, detecting increased thyroid activity during pertechnetate scintigraphy by subcutaneous injection is an accurate and reproducible test for feline hyperthyroidism.
Department of Clinical Sciences, Cornell University, College of Veterinary Medicine, Ithaca, NY 14853, USA. rpage@rossvet.edu.kn
Richard B
RB
Page
Peter V
PV
Scrivani
Nathan L
NL
Dykes
Hollis N
HN
Erb
Jeff M
JM
Hobbs
D000818:Animals; D002371:Cat Diseases / Q000000981:diagnostic imaging*; D002415:Cats; D005260:Female; D006980:Hyperthyroidism / Q000000981:diagnostic imaging / Q000662:veterinary*; D007279:Injections, Subcutaneous / Q000662:veterinary; D008297:Male; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011877:Radionuclide Imaging / Q000662:veterinary; D019275:Radiopharmaceuticals / Q000008:administration & dosage; D012680:Sensitivity and Specificity; D013670:Sodium Pertechnetate Tc 99m / Q000008:administration & dosage; D013961:Thyroid Gland / Q000000981:diagnostic imaging / Q000378:metabolism
D019275:Radiopharmaceuticals; D013670:Sodium Pertechnetate Tc 99m