Diffuse reflectance spectra of the palpebral conjunctiva and its utility as a noninvasive indicator of total hemoglobin

The palpebral conjunctiva is an attractive location to quali- tatively examine for the presence of anemia; however, this method of diagnosis has not been shown to be accurate. A spectroscopic exami- nation of the palpebral conjunctiva enables the use of a quantitative parameter as a basis for diagnoses. Visible range diffuse reflectance spectra from the palpebral conjunctiva are examined from 30 patients and hemoglobin levels are extracted from these signatures using both a partial least-squares PLS multivariate regression model and a dis- crete spectral region model. Hemoglobin concentration derived from both these models is compared to an in vitro measurement of hemo- globin. Root mean squared errors of cross validation for the two ana- lytical methods are 0.67 g/dL and 1.07 g/dL, respectively. Conjunc- tival reflectance spectra coupled with a PLS analysis achieve an enhanced specificity and sensitivity for anemia diagnoses over re- ported observational studies using the palpebral conjunctiva and achieve improved accuracy to other reported methods of noninvasive hemoglobin measurement. © 2006 Society of Photo-Optical Instrumentation Engi-