Infant Heel Dermal Carotenoids Are Measured Rapidly and Reliably by Portable Reflection Spectroscopy

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Abstract Objectives Dermal carotenoid assessment by portable reflection spectroscopy offers a rapid and non-invasive assessment of carotenoid status. However, feasibility, validity, and reliability has not been assessed in diverse, young infants. We hypothesize that dermal carotenoid measurement of infants’ heels and fingers will be feasible, reliable, and valid. Methods Dermal carotenoid intensity was measured by portable reflection spectroscopy (Veggie Meter) at the index finger and heel of the foot in the first fourteen, 4 month old subjects of the Baylor Infant Biomarker of Nutrition Study. Up to 6 reads were acquired in which the skin was correctly positioned and held still. Infant feeding was assessed by a 7-day infant FFQ. Feasibility was assessed by the time to acquire reads, and reliability was assigned if 3 reads with a 10% CV (conforming reads) could be obtained, per the manufacturer's specifications for adult readings. Internal validity was assessed by correlation between average heel and finger reflection scores. Differences between formula and breastfed infant reflection scores were compared. Results Infants (n = 14, 50% female) were of diverse race-ethnicities (71% White, 21% African American, 7% Asian, and 36% Hispanic), but neither sex nor race-ethnicity predicted reflection score. Three heel reads could be acquired more rapidly than three finger reads (1.1 ± 0.2 min vs. 1.5 ± 0.5 min, P = 0.03), and completion of all finger measurements took longer (4.8 ± 3.2 min) than all from the heel (2.6 ± 1.7 min, N.S.). Acquisition of reliable heel reflection scores was more feasible, with 86% of subjects providing conforming heel reads, but only 36% of subjects providing conforming finger reads. Finger and heel reflection scores were positively correlated (r = 0.73, P = 0.003) within subjects, indicating internal validity. Finger and heel reflection scores were greater in human milk-fed infants (n = 10) compared to breastfed (n = 4) (107 ± 9 vs. 49 ± 14 reflection score, P = 0.005) Conclusions Score differences by feeding method suggest sensitivity to detect differences in dietary carotenoid exposure. Portable reflection spectroscopy of infants’ heels offers a feasible, reliable, and valid measure of dermal carotenoids in infants and should be further validated as a biomarker of infant carotenoid status. Funding Sources Texas Children's Hospital, USDA.