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Determination of serum bilirubin by skin reflectance: effect of pigmentation
Insights
This study validates a noninvasive optical method for estimating serum bilirubin in infants. The technique accurately measures bilirubin levels across different skin tones, showing potential for clinical use.
Area of Science:
- Biomedical Optics
- Neonatal Medicine
- Medical Physics
Background:
- Neonatal jaundice is common, requiring accurate bilirubin monitoring.
- Current methods for serum bilirubin measurement are invasive.
- Noninvasive optical techniques offer a promising alternative for bilirubin assessment.
Purpose of the Study:
- To evaluate a noninvasive optical method for serum bilirubin estimation in a larger, diverse infant population.
- To investigate the influence of natural skin pigmentation on the method's accuracy.
- To develop a physical model explaining the relationship between skin reflectance and serum bilirubin concentration.
Main Methods:
- Spectral reflectance measurements (380-800 nm) and concurrent serum bilirubin levels were collected from 58 white and 45 black full-term infants.
- Multiple linear regression analysis using various wavelength combinations was performed.
- A physical model utilizing a transformed Kubelka-Monk function was developed to correlate reflectance with bilirubin concentration.
Main Results:
- High correlation coefficients were achieved for both white (r=0.831) and black (r=0.877) infant groups using regression analysis.
- The physical model demonstrated a linear relationship between a specific Kubelka-Monk function and serum bilirubin levels (r=0.778 for white, r=0.865 for black infants).
- Standard errors of estimate were comparable to routine laboratory methods, indicating clinical feasibility, and skin pigmentation did not significantly obscure the results.
Conclusions:
- The noninvasive optical method for serum bilirubin estimation is accurate and reliable in full-term infants, regardless of skin pigmentation.
- The developed physical model provides a scientific basis for the observed relationship between skin spectral properties and bilirubin levels.
- This technique holds significant potential for widespread clinical application in neonatal care, offering a noninvasive and effective alternative to blood tests.
Abstract:
A noninvasive optical technique by which serum bilrubin can be estimated from skin spectral reflectance measurements has been further investigated. The original work on 30 healthy, full-term white infants and an independent study on 14 white and 30 black infants demonstrate that the method has potential not only for clinical use, but also for the study of the transport of bilrubin to, from and within the skin. The objectives of the present study are to evaluate the method on a larger sample population with special attention to natural skin pigmentation effects and the development of a physical model of the tissue to explain the relationship between serum bilrubin concentration and skin reflectance. Reflectance spectra (380-800 nm) and concurrent serum bilirubin measurements were taken on a sample population of 58 white and 45 full-term black infants (1-3 days of age). Multiple linear regression analysis, comprised of six wavelengths gave a correlation coefficient, r = 0.831 for the white infant group. For the black infant group, a five wavelength analysis provided r = 0.877 with the standard error of estimate being +/- 1.46 mg/100 ml for both groups. The model for establishing a physical basis for the relationship shows that a transformed, normalized Kubelka-Monk function xi (460, 510, 420) is linearly related to serum bilrubin concentration. This function is determined from the spectral reflectance values at three wavelengths, 420, 460, and 510 nm. The wavelength combination is such that effects due to hemoglobin and melanin pigments are minimized. Regression analysis showed that r = 0.778 and r = 0.865 for the white and black infant groups, respectively, with standard error of estimates being +/- 1.4 mg/100 ml for both groups. Routine determinations of total serum bilrubin by laboratory methods have standard errors of estimate ranging from +/- 1 to 1.5 mg/100 ml. Thus, the method herein described shows that the relationship between skin reflectance and serum bilrubin in full-term infants is close to the acceptable limits for clinical use. Furthermore, this work shows that skin pigmentation does not obscure this relationship.