Accuracy of a Photo-based Smartphone Application to Assess Salivary Cortisol Sampling Time in Adolescents

Accurate assessment of saliva sampling time is essential for studies that collect cortisol sample in ambulatory settings. This study examined the sampling time assessed by user-submitted photos via a mobile application (ZEMI) compared with MEMSCaps™. Intra-class correlation coefficient (ICC) of the time differences between when the 16 adolescents in the study were prompted to collect the sample and (1) when the MEMSCaps™ was opened (Time M ), and (2) when photos of the corresponding sample were submitted (Time Z ) was computed to evaluate the agreement of sampling times. The average Time M and Time Z 12.06 ± 65.80 and 16.13 ± 52.07 minutes, respectively. The pooled ICC between Time M and Time Z was 0.986 (95% CI: 0.959–0.995), suggesting excellent correspondence between the two measurements.