Introduction: Salivary cortisol is used as an indicator of stress level and a recommended screening test for Cushing syndrome. The normal reference interval for salivary cortisol is dependent on the analytical methodology and the population studied and hence, establishment of a local population-based reference interval is recommended.
Materials and methods: A total of 129 healthy blood donors and staffs of Penang General Hospital were recruited from June 2018-May 2019. Paired (morning and late-night) saliva samples were collected from individuals aged between 18 and 60 years old with no history of chronic medical illness. Salivary cortisol was assayed using electrochemiluminescence immunoassay technique. Non-parametric statistics were used for calculation of reference interval and 90% confidence intervals (90% CIs).
Results: The reference interval for morning and latenight salivary cortisol was 2.09 - 22.63 nmol/L and <12.00 nmol/L, respectively.
Conclusion: The locally-derived adult reference intervals for morning and late-night salivary cortisol concentration was determined and varied with previous studies emphasising the need in establishing individual laboratory reference interval.