Efficiency of inferior petrosal sinus sampling in the diagnosis of Cushing's disease and comparison with magnetic resonance imaging.

OBJECTIVE: The purpose of this study is to assess the efficiency of inferior petrosal sinus sampling (IPSS) in the diagnosis of adrenocorticotropic hormone-dependent Cushing's disease and to compare it with magnetic resonance imaging (MRI).

METHODS: The diagnostic efficiency of IPSS in the differentiation of pituitary Cushing's disease from ectopic Cushing's disease was retrospectively evaluated in 37 patients who had IPSS in our clinic. Six patients were excluded from the study due to missing data. Hypophysis MRI examinations of 31 patients before IPSS were also evaluated. The contributions of MRI and IPSS to the detection of pituitary adenoma and the determination of lateralization were researched.

RESULTS: Bilateral IPSS was successfully performed in 30 patients of the 31 patients in the study group. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of IPSS in differentiating between central and ectopic Cushing's syndrome before corticotrophin-releasing hormone (CRH) stimulation were 93.3%, 100%, 100%, 33.3%, and 93%, respectively, whereas after CRH stimulation were 100%, 100%, 100%, 100%, and 100%, respectively. The accuracy of both the rates was significantly higher compared with MRI.

CONCLUSION: IPSS has the highest diagnostic efficiency in differentiating central Cushing's disease from ectopic Cushing's disease.