Salivary cortisol sampling compliance: comparison of patients and healthy volunteers

Problems of compliance with in vivo data collection and treatment protocols have been identified. This study investigated compliance with salivary cortisol sampling in a 7-day protocol. Impact of non-compliance on cortisol data was evaluated.

Female fibromyalgia patients were matched with healthy female volunteers and randomized to Aware or Unaware conditions regarding objective monitoring of their sampling compliance. The protocol entailed collecting five saliva samples at prescribed times on each of 7 consecutive days. Participants self-reported time of each sample, and electronic monitor caps provided an objective date and time stamp of each sample.

Objective compliance among participants unaware of monitoring was 71%, though their self-reported compliance was 93%. Aware participants' objective compliance was 90% which was consistent with self-reported compliance of 93%. Within-subject comparison of early morning rise and day slope of cortisol for compliant and non-compliant samples found significant differences with non-compliant samples resulting in flatter slopes. Patients were somewhat more compliant than healthy volunteers. Slight decrements in compliance were found for the afternoon sample (1600 h) and for the last 3 days of sampling. Compliance did not differ on weekdays versus weekends.

Self-report of compliance in a salivary cortisol sampling protocol substantially overestimates actual compliance in the absence of objective monitoring. Non-compliance with the sampling protocol results in cortisol data that significantly differs from compliant data. Awareness of electronic monitoring of sampling results in satisfactory compliance.