مقايسه روش انفوزيون 7 ساعته دگزامتازون با روش كلاسيك دو روزه دگزامتازون با دوز بالا در تشخيص افتراقي سندرم كوشينگ گزارش 207 مورد

Intravenous Dexamethasone suppression test in comparison with 2day IIDDST test in the differential diagnosis of Cushingʹs syndrome: A report of 207 cases

lntroduction: Etiologic diagnosis of cushingʹs syndrome is a major challenge in its investigation and treatment. Classical oral HDDST has shown differing sensitivity and specificity in various studies. The IV DEX suppression test with elimination of intestinal absorption factor has been in use since 1973. This study was designed to evaluate the diagnostic power of IV the DEX test in comparison with classic oral HDDST. Materials and Methods: Two hundred and seven consecutively referring patients with Cushingʹs syndrome diagnosed by screening and LDDST were enrolled. Two days oral HDDST and 7h-h DEX infusion test were performed in all cases. ln the infusion test, decrease in serum cortisol to less than 50% of basal level was consistent with a positive response. In the classic oral test suppression of UFC ?50 % and 90% of basal levels assumed as positive response. Etiologic diagnosis was confirmed by imaging and pathologic specimens. Results: Mean age of patients with ectopic ACTH (EAS) was (58.2±12.6 vs 31.0±10.0) which was higher than athat of pituitary and adrenal cases (p<0.01). Weight loss, weakness and ecchymosis and hypertension were more prevalent in EAS (p<0.05). Positive response to infusion test was detected in 98% of Cushingʹs disease cases and no false positive response was detected in EAS and adrenal cases; however oral HDDST (90% cutoff level) had 8.1% false positive. In differential diagnosis of pituitary versus non-pituitary tumors, IV DEX test had sensitivity of 98.1%, specificity of 100% and accuracy of 98.5 compared with classic oral which had sensitivity of 98.1, specificity of 93% and accuracy of 97%. ROC curve showed AUC of 0.99 in infusion test versus 0.96 in the classic oral HDDST with 90% suppression. Conclusion: In the present study, lV DEX test with its increased rapidity and higher accuracy as well as higher specificity, in comparison the classic oral HDDST, can be a better diagnostic choice in the differential diagnosis of Cushingʹs syndrome.