Non-invasive jaundice detection using spectral-band expansion from RGB images and direct hyperspectral images

The gold standard for diagnosing jaundice has been measuring serum bilirubin level through venous blood sampling. Despite its high accuracy, this method is invasive, requires clinical infrastructure, and thus may delay jaundice diagnosis. Here, we use two spectral-image techniques, image spectral-band expansion and hyperspectral imaging (HSI) to analyze the spectral features of patients’ sclera and skin for comparison with serum bilirubin levels. Image spectral-band expansion is compatible with standard RGB cameras or smartphones and thus widely available at relatively low costs, while HSI captures and processes image information across a wider range of wavelengths at higher spectral resolution for each pixel in an image. Ocular RGB-based analysis showed strong predictive performance with R² = 0.9880 and a Pearson correlation coefficient of 0.9945. HSI revealed distinctive spectral signatures in jaundiced skin not visible in RGB images. Jaundiced skin exhibits notably reduced redness at 600–740 nm, but elevated reflectance emerges around 750–850 nm, followed by three key crossover points at approximately 850 nm, 950 nm, and 980 nm versus normal skin. These near-infrared spectral features indicate that extending spectroscopic jaundice diagnosis beyond 740 nm could enhance diagnostic accuracy.