740 - Mapping the longitudinal trajectory of skin pigmentation in critically ill infants

Publication Number: 1717.740

Megha Sharma, University of Arkansas for Medical Sciences, Little Rock, AR, United States; Simon Chung, University of Arkansas for Medical Sciences, Little Rock, AR, United States; Andrew W. Brown, Arkansas Children’s Research Institute, Little Rock, AR, United States; Sarah E. Diamond, University of Arkansas for Medical Sciences College of Medicine, Little Rock, AR, United States; Erinn M. Roblee, University of Arkansas for Medical Sciences College of Medicine, Little Rock, AR, United States; Mario Schootman, University of Arkansas for Medical Sciences College of Medicine, Springdale, AR, United States; Peter Mourani, University of Michigan Medical School, Ann Arbor, MI, United States

Background: Recent reports of pulse oximeter inaccuracy (POI) in patients with dark skin pigmentation highlight the need for objective measurement of skin pigmentation to quantify the magnitude of this inaccuracy. However, there are limited data on how best to assess skin pigmentation in neonates. No studies have longitudinally tracked skin pigmentation during infancy. Such data are essential for studies evaluating POI in neonates, as dynamic changes in skin maturation and pigmentation may influence device performance and should be considered when designing and refining pulse oximeter technology.

Objective: While focus of the parent prospective study is to quantify the extent of POI in neonates of diverse skin pigmentation, we are conducting an ancillary/nested study evaluating the longitudinal trajectory of skin pigmentation.

Design/Methods: Eligible infants are 0-3 months of age and have arterial lines in the neonatal and cardiac ICUs. Skin pigmentation measures are obtained weekly from enrollment to 6 months using a spectrophotometer at the pulse oximeter probe site (dorsal foot). This device reports comprehensive skin color metrics, including a Melanin Index (skin darkness), Erythema Index (redness), Individual typology angle, and the color coordinate L (skin lightness on a Black to White scale). We fit a linear mixed-effects model for these color metrics with gestational age, maternal race/ethnicity, and age as fixed effects. Age and its interactions with race/ethnicity were modeled using natural spline terms. A random intercept for each patient was included to account for within-subject correlation. Marginal predictions with 95% CI were calculated to visualize the trajectory of these skin color metrics across age, with corresponding skin tones rendered according to the LCh color space.

Results: To date, 172 of 200 planned neonates have been enrolled (156 analyzed), with 116 completing at least 4 weeks of follow-up for a total of 962 measurements. The cohort (Table 1) comprised 63% Non-Hispanic White (NHW), 28% Non-Hispanic Black (NHB); 62% male; and 34% preterm. Preliminary analyses show similar pigmentation at birth across race/ethnicity groups. Over time, Melanin Index remains elevated in NHB neonates, while it declines and plateaus in NHW neonates (Figure 1, 2).

Conclusion(s): This study provides the first longitudinal characterization of skin pigmentation trajectory in critically ill infants. Pigmentation follows distinct courses in NHB and NHW neonates. If pigment-related POI exists, its degree and consequences may vary across time points as pigmentation changes, in these vulnerable patients.

Table 1. Demographic characteristics of study cohort.


Figure 1. Longitudinal trajectory of skin pigmentation in first six months of age.
This plot depicts colorimetric measures reported by Spectrophotometer, SkinColorCatch, over serial weekly measurements on the Y-axis, with chronological age in days on the X-axis. Each dot represents a value of the colorimetric measure for a neonate. The solid line shows the marginal prediction of the colorimetric measure from mixed-effects linear regression model, the shaded areas represent the 95% confidence intervals. Melanin Index and Erythema index are both reported on an arbitrary scale of 0-999, Individual Typology angle (ITA) is reported on a scale of -90° to +90°, L is reported on a scale of 0 (Black) to 100 (White).

Visual representation of skin pigmentation change over time for NHB (solid arrow) and NHW (dotted arrow) infants.
Visual representation of skin pigmentation for NHB (solid arrow) and NHW (dotted arrow) infants. This plot reproduces skin color in a 3-D space using colorimetric coordinates obtained from the spectrophotometer which captures a color's brightness (lightness, L), intensity or vividness (chroma, c) and the actual color eg, red, green, blue (hue, h). In the quadrant below, the hue (h) and chroma (c) are displayed in 2-D space as angle 0-90° and radius (0-35) respectively. Length of arrow from head to tail represents chronological age (0-180 days). The band around the two arrows captures the lightness L in addition to the h and c coordinates for the NHB and NHW groups. [the figure on the right depicts Lch color space diagram; Figure without copyright]