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

A cross-sectional research study was conducted across eight sites in the USA. 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 CV and 95 % CI of each device/site; hypothesised to be ≤ 6 %. Inter-device comparisons included ICC, absolute relative differences (ARD) and 95 % CI, and equivalence; both hypothesised to be ≤ 10 %.

Eight sites across the USA.

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 %.

Intra-device ICC ranged from 0·77 to 0·99. The CV ranged from 6·2 to 14·2 %, with an average of 8·8 %. A majority (63 %; n 10) of the Veggie Meter® devices had significantly higher CV from the hypothesised 6 %. Inter-device ICC ranged from 0·58 to 0·94. The ARD ranged from 7·5 to 22·0 %, with an average of 13·9 %. ARD in a majority (n 5) of sites was significantly higher than the hypothesised 10 %. Five sites (63 %) demonstrated equivalence below the hypothesised 10 %.

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.