Examining Intra- and Inter-Device Reliability of Pressure-Mediated Reflection Spectroscopy in a Multi-State Sample of Healthy Adults.

Objective: To examine the intra- and inter-device reliability of devices using pressure-mediated reflection spectroscopy (the Veggie Meter®).

Design: A cross-sectional research study was conducted across 8 sites in the United States. Using two Veggie Meters® at each site, participants completed five, counter-balanced pairs of finger scans. Intra-device comparisons included intra-class correlation coefficients (ICC) and calculation of the Coefficient of Variation (CV) and 95% confidence intervals (CI) of each device/site; hypothesized to be ≤ 6%. Inter-device comparisons included ICC, Absolute Relative Differences (ARD) and 95% CI, and equivalence; both hypothesized to be ≤ 10%.

Setting: Eight sites across the United States.

Participants: Across sites, participants' (n=282) average age ranged 24.7-39.0 years; sex ranged 60.0%-85.7% women, and Non-Hispanic White ranged 20.0%-94.3%.

Results: Intra-device ICC ranged from 0.77-0.99. The CV ranged from 6.2%-14.2%, with an average of 8.8%. A majority (63%; n=10) of the Veggie Meter® devices had significantly higher CV from the hypothesized 6%. Inter-device ICC ranged from 0.58-0.94. The Absolute Relative Difference (ARD) ranged from 7.5%-22.0%, with an average of 13.9%. ARD in a majority (n=5) of sites was significantly higher than the hypothesized 10%. Five sites (63%) demonstrated equivalence below the hypothesized 10%.

Conclusions: Our study demonstrates the intra-device and inter-device reliability to be moderate to high, as per ICC. The observed margin of difference within a device was up to 14%, with an average of 9%. The observed margin of difference between devices was up to 22% with an average of 14% between devices.