Diffuse reflectance spectroscopy and RGB-imaging:  a comparative study of non-invasive haemoglobin assessment

Abstract Non-invasive assessment of haemoglobin (Hb) level in blood is a hot spot in point-of-care biomedical diagnostics. Several optical methods are suggested as a solution, some of them being approved for clinical use. Still, there is no consensus on the accuracy of optical techniques, the quality of Hb assessment on different tissue sites, and whether a combined use of several optical techniques can improve the quality of Hb level prediction. In this work we examined the capabilities of two optical techniques — diffuse reflectance spectroscopy and RGB-imaging of the skin and fingernails areas — for detection of low blood Hb level. The test sample consisted of 240 adult volunteers with 70 volunteers exhibiting Hb level lower than 120 g/L. We show that using simple descriptors of the diffuse reflectance spectrum of the forearm skin and fingernails, it is possible to accurately predict a decrease in blood Hb concentration (ROC-AUC = 0.84 ± 0.08), while RGB-imaging shows similar performance when applied to the fingernail regions (ROC-AUC = 0.83 ± 0.07). The joint use of predictions from two optical methods increases the accuracy of non-invasive determination of the Hb level determination. The obtained results suggest that implementation of multimodal optical techniques is prospective for clinical use and screening purposes.