Skin color influences transcutaneous bilirubin measurements: a systematic in vitro evaluation.

OBJECTIVE: Concerns have been raised about the effect of skin color on the accuracy of transcutaneous bilirubin (TcB) measurements, a widely used method for hyperbilirubinemia diagnosis in newborns. Literature is inconclusive, with both reported under- and overestimations of the TcB with increasing skin pigmentation. Therefore, the influence of skin color on TcB measurements was systematically evaluated in a controlled, in vitro setting. METHODS: A bilirubin meter (JM-105) was evaluated on layered phantoms that mimic neonatal skin with varying dermal bilirubin concentrations (0-250 µmol/L) and varying epidermal melanosome volume fractions (0-40%; light-dark skin color). RESULTS: TcB measurements were influenced by skin pigmentation. Larger mimicked melanosome volume fractions and higher bilirubin levels led to larger underestimations of the measured TcB, compared to an unpigmented epidermis. In the in vitro setting of this study, these underestimations amounted to 26-132 µmol/L at a TcB level of 250 µmol/L. CONCLUSION: This in vitro study provides insight into the effect of skin color on TcB measurements: the TcB is underestimated as skin pigmentation increases and this effect becomes more pronounced at higher bilirubin levels. Our results highlight the need for improved TcB meter design and cautious interpretation of TcB readings on newborns with dark skin. IMPACT: Key message: Skin color influences transcutaneous bilirubin measurements: the darker the skin, the larger the underestimation. What this study adds to existing literature: Existing literature is inconclusive regarding the influence of skin color on transcutaneous bilirubin measurements. This study systematically evaluates and clarifies the influence of skin color on transcutaneous bilirubin measurements in a controlled, in vitro setting. IMPACT: This study aids to better interpret the measured TcB level in patients with varying skin colors, and is particularly important when using TcB meters on patients with dark skin colors.

Design and characterization of color printed polyurethane films as biomedical phantom layers.

We propose a new, user-friendly and accessible approach for fabricating thin phantoms with controllable absorption properties in magnitude, spectral shape, and spatial distribution. We utilize a standard office laser color printer to print on polyurethane thin films (40 - 60 µm), commonly available as medical film dressings and ultrasound probe covers. We demonstrate that the optical attenuation and absorption of the printed films correlate linearly with the printer input settings (opacity), which facilitates a systematic phantom design. The optical and acoustic properties of these polyurethane films are similar to biological tissue. We argue that these thin phantoms are applicable to a wide range of biomedical applications. Here, we introduce two potential applications: (1) homogeneous epidermal melanin phantoms and (2) spatially resolved absorbers for photoacoustic imaging. We characterize the thin phantoms in terms of optical properties, thickness, microscopic structure, and reproducibility of the printing process.