Objective
Salivary cortisol measurement plays an important role in the evaluation of adrenal function. Its high correlation with free serum cortisol, the easy of sampling and the limited presence of interfering steroids, generated multiple recent studies of its application, in special in the screening of adrenal hyperfunction. In this paper we present our experience in the development of a high pressure liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method for salivary cortisol and cortisone measurement.
Materials and methods
For this study we used 181 saliva samples from our routine diagnostic laboratory. The HPLC-MS/MS method was based on a Waters Quattro Premier tandem mass spectrometer with an electrospray probe. After derivatization with hydroxylamine transitions monitored included cortisol and cortisone. An in-house radioimmunoassay (RIA) was used for salivary cortisol results comparison.
Results
Functional sensitivity was 24 ng/dL for cortisol and linearity from 24 to 1929 ng/dL. Saliva cortisol values obtained in the 181 samples presented a median of 52 ng/dL with 5‐95% percentile of 24 and 374 ng/dL. With the RIA the results were 86, 25 and 436 ng/dL, respectively, with values for RIA being significantly higher (P<0.0001) and high correlation (r=0.8312, P<0.0001). Cortisone measured in 159 samples showed a median of 278 ng/dL, with 5‐95% percentile of 100 and 1,133 ng/dL. Correlation with cortisol values was significant (r=0.820, P<0.0001).
Conclusion
We conclude that the HPLC-MS/MS method compares favorably with the RIA for salivary cortisol measurement, with the additional possibility of concomitant cortisone measurement and the evaluation of 11βHSD2 activity.
Salivary cortisol; salivary cortisone; mass spectrometry; radioimmunoassay; hypercortisolism screening
