Non-invasive determination of hemoglobin by digital photography of palpebral conjunctiva.

The objective of this study was to determine whether digital photography could be used to calculate hemoglobin. This prospective blinded study was conducted in a tertiary care Emergency Department (ED). A convenience sample of 65 patients provided consent; 44 patients were enrolled for formula derivation and 19 for prospective analysis. Hemoglobin concentration in blood was determined by a cell counter. Software was developed to predict the hemoglobin value based on a formula derived using the images and known hemoglobin values from a derivation set of patients. Pearson's rank order correlation between the calculated and measured hemoglobin was r(77) = 0.634, p < 0.01 for the derivation group and r(36) = 0.522, p < 0.01 for the evaluation group. It is possible to derive an objective method that correlates conjunctiva color with measured hemoglobin and, when applied prospectively, is able to predict hemoglobin concentration in ED patients. This technology has broad applications in regions with limited resources.