In vivo Raman spectroscopy discriminates between FLG loss-of-function carriers vs wild-type in day 1-4 neonates

Background: Carriers of loss-of-function mutations in the filaggrin gene (LoF FLG) have less natural moisturizing factor (NMF) in their stratum corneum (SC) and an increased risk of atopic dermatitis (AD). Natural moisturizing factor can be measured noninvasively by Raman spectroscopy. The use of Raman-derived NMF at birth to screen for FLG genotype could inform targeted AD prevention, but values in neonatal populations are largely unexplored. Objective: To examine the associations between Raman-derived neonatal NMF measurements and FLG genotype. Methods: Natural moisturizing factor was measured by Raman spectroscopy in the SC of the thenar eminence within 4 days of birth in 139 term neonates. Filaggrin genotyping was performed for 117 neonates (84%). Results: The mean (SD) NMF was 0.37 (0.11) g/g protein, with values increasing across the first 3 days (day 1 vs 3: 0.29 [0.09] vs 0.43 [0.08, P <.001]). Twelve infants (10.3%) were carriers of LoF FLG, all heterozygous. Natural moisturizing factor was lower in LoF FLG carriers compared with wild-type (0.27 [0.08] vs 0.38 [0.11] g/g protein, P ≤.001). Natural moisturizing factor had good discriminatory power for FLG genotype (area under the receiver operating curve [AUROC]: 0.79; 95% CI: 0.66, 0.91; P ≤.001). This improved after correcting day 1 and 2 measurements to day 3 (AUROC: 0.83; 95% CI: 0.75, 0.92; P <.001). Conclusion: This study suggests that Raman-derived NMF measured in the early postnatal period may have the potential to classify by FLG genotype. The full translational value of this needs to be determined.

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