Budget impact of using midnight salivary cortisol in the diagnosis of hypercortisolism

[Background] A single midnight serum cortisol (MSC) test has been reported to possess the best sensitivity and specificity for diagnosing Cushing's syndrome (CS). However, this test requires patient hospitalization, making it costly. This paper aims to compare the hospital budget impact and accuracy of using midnight salivary cortisol (MSVC), as opposed to MSC, in the diagnosis of hypercortisolism.
[Methods] 77 patients with at least two high urinary free cortisol (UFC) values (>360 nmol/24. h) were selected from 611 patients with clinical symptoms of CS. The costs of the method to confirm the diagnosis of hypercortisolism was calculated comparing Option A using MSC (UFCx2, low-dose dexamethasone suppression test [LDDST]) that requires patient hospitalization versus Option B using MSVC (UFCx2, LDDST) in which the evaluation is done outside the Hospital. A budget impact analysis for one year was developed, and a sensitivity analysis in different scenarios was performed. Reproducibility and diagnostic performance of MSVC and MSC were also measured.
[Results] Salivary cortisol is a sound analytical method for evaluating free serum cortisol due to its classification accuracy, good imprecision, linearity, and stability. AUCROC comparison between MSVC and MSC shows no significant differences. The substitution of the MSC for MSVC in our hospital could save between €16,762 and €132,804 in one year.
[Conclusions] The use of MSVC in the diagnosis of hypercortisolism can result in a substantial decrease in the budget impact, without losing diagnosis accuracy and reliability, a significant advantage considering the current emphasis on reducing the financial burden of health care. © 2011 Elsevier B.V.
This work has been supported by the Fondo de Investigación Sanitaria (FIS), ETESPI08/90541 2009–2010 and by Plan Andaluz de Investigación (CTS-444). We thank S. Pelaez for his review of methodology and statistics, and L. Santamarina for her revisions of the English version of the manuscript.