Inter‐device concordance of Veggie Meter, a reflection spectroscopy to measure skin carotenoids

The Veggie Meter® (VM) is a refraction spectrometer that detects skin carotenoids. We tested the variability of the two modes (single-scan and averaging modes) of four VMs of three different versions (VM-1, 2, 3, 4) with 92 healthy volunteers. Both the modes exhibited a high intraclass correlation coefficient; however, the averaging mode had a significantly lower coefficient of variance than the single-scan mode. The Bland-Altman analysis showed a systematic error between VM-1 and other three VMs. The actual errors between the VM-1 and the other three VMs in the averaging mode were 7.4, 10.4, and 11.8% of the median of VM scores, but the errors could be reduced to 2.8, 6.3, and 7.0% by compensating VM scores using the regression equations. Averaging mode had higher accuracy than single-scan mode. The reliability of the VMs was validated by the small CV and high ICC. The error was improved using linear regression compensation.