Validity and reliability evidence of a point of care assessment of salivary cortisol and α-amylase: a pre-registered study

Kagan J Ducker; Robin L J Lines; Michael T Chapman; Peter Peeling; Alannah K A McKay; Daniel F Gucciardi

doi:10.7717/peerj.8366

Validity and reliability evidence of a point of care assessment of salivary cortisol and α-amylase: a pre-registered study

PeerJ. 2020 Jan 8:8:e8366. doi: 10.7717/peerj.8366. eCollection 2020.

Authors

Kagan J Ducker¹, Robin L J Lines¹, Michael T Chapman¹, Peter Peeling², Alannah K A McKay^{2

3}, Daniel F Gucciardi¹

Affiliations

¹ School of Physiotherapy and Exercise Science, Curtin University, Perth, Western Australia, Australia.
² School of Human Sciences (Exercise and Sport Science), The University of Western Australia, Perth, Western Australia, Australia.
³ Australian Institute of Sport, Belconnen, Australian Capital Territory, Australia.

Abstract

Purpose: The iPro Cube is a small portable point-of-care device designed to analyse salivary markers of stress in a user-friendly manner (e.g., fast, convenient). Our aim was to test the reliability and validity of the iPro Cube to measure salivary cortisol and α-amylase as compared to the common laboratory standard method (ELISA immunoassay) prior to and after moderate intensity exercise.

Methods: The study was a repeated measures, pre-registered design, and statistical framework that incorporated prior knowledge directly into the estimation process. Twenty-nine individuals (age = 27.4 ± 6.6 y; body-mass = 70.8 ± 11.3 kg; height = 1.74 ± 0.92 m; 18 males) completed a single PWC_75%HRmax, with repeated measures of salivary cortisol and -amylase pre, immediately post, and 30 min post-exercise.

Results: Correlation between the iPro Cube and laboratory-based assessments of salivary cortisol was moderate-to-large (0.53 > r < 0.81) across all three testing points. In contrast, correlation between the iPro Cube and laboratory-based assessments of -amylase was small-to-moderate (0.25 > r < 0.46). We found a large correlation between duplicate samples of iPro Cube cortisol assessment (0.75 > r < 0.82), and a moderate-to-large correlation for -amylase (0.51> r < 0.77).

Conclusions: The iPro Cube is capable of taking measures of salivary cortisol that are moderately correlated to values obtained via ELISA immunoassay, however the unit underestimates salivary cortisol and overestimates salivary -amylase at rest and post-moderate intensity exercise. It is recommended that researchers continue using standard laboratory techniques to assess these salivary stress markers.

Keywords: Exercise; Psychophysiology; Saliva; Stress.

Grants and funding

The Commonwealth of Australia supported this research through the Australian Army and a Defence Science Partnerships agreement of the Defence Science and Technology Group, as part of the Human Performance Research Network (ID7085). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.