Limited Invasive Protocol: Optimizing Diagnostic Modalities in ACTH Mediated Cushing’s Syndrome

ABSTRACT

Background

To limit the role of bilateral inferior petrosal sinus sampling (BIPSS) in distinguishing between Cushing's disease (CD) and Ectopic Cushing's syndrome (ECS), recent reports have proposed a non-invasive approach based on combination of biochemical testing and radiological imaging as an alternative to conventional invasive strategy (CIS). However, this strategy requires further validation. The current study aimed to evaluate two limited invasive protocols (LIP-1 and LIP-2) in limiting the role of BIPSS, while maintaining a diagnostic accuracy similar to CIS.

Methods

It was a single centre study, conducted in individuals with adrenocorticotrophic (ACTH) dependent Cushing's syndrome (CS). LIP were based on performing high-dose dexamethasone suppression [>50% cut-off in first (LIP-1) and >80% in second (LIP-2)] and magnetic resonance imaging of sella in all individuals, and selective use of computed tomography of chest and abdomen prior to BIPSS. These LIP were evaluated for limiting the use of BIPSS, their accuracy and cost in comparison to CIS.

Results

Of the 206 individuals, 114 (97 of CD and 21 of ECS) were eligible for the current study. Using LIP-1, LIP-2 and CIS, BIPSS could have been avoided in 62.3%, 35.9% and 25.4% individuals, respectively. The positive predictive value (PPV) for CD using LIP-1 and LIP-2 was 98.9% and 100%, respectively. The cost per patient evaluated using LIP-1, LIP-2 and CIS was US$ 602.21, 966.81 and 1107.78, respectively.

Conclusion

LIP represent an equally accurate, less invasive and more cost-effective alternative to conventional invasive strategy for distinguishing between CD and ECS.