Background: Although early studies with IPSS reported a diagnostic sensitivity and specificity approaching 100%, additional experience has revealed a false negative rate of 110%. Previous studies have suggested that the measurement of other anterior pituitary hormones may be useful as a guide to the effectiveness of cannulation and to improve diagnostic accuracy.
Method: In this retrospective cohort study, we reviewed all patients who had undergone IPSS for investigation of ACTH dependent hypercortisolism, between 2005 and 2010. The normalised ACTH/Prolactin inferior petrosal sinus:peripheral ratio were calculated to assess the accuracy of the sampling procedure.
Results: A total of 83 patients underwent investigation with IPSS. 67 patients initially had a positive IPSS result (i.e. a basal central:peripheral ACTH ratio >2.0 and >3.0 post CRH). However when the concurrent prolactin data was used, 6 patients were additionally found to have positive results suggestive of pituitary Cushings. The Prolactin normalised ACTH IPS:Peripheral ratios were all greater than 0.8 in patients with proven Cushings disease, whereas they were all less than 0.6 in proven ectopic ACTH syndrome. The diagnosis was subsequently confirmed histologically in 72 of the patients.
Conclusions: Using Prolactin as a concurrent index of pituitary venous effluent helps us recognise whether pituitary venous blood has been accurately sampled. Normalising the IPS:peripheral ratios with Prolactin helps to improve the accuracy of the result and reduces the false negative rate.
Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.