Test of a noninvasive instrument for measuring hemoglobin concentration

A colorimetric instrument for the noninvasive quantification of hemoglobin, designed using color shades resembling those observed in the conjunctiva, was tested. The instrument's colors are contrasted against the color of the conjunctiva to measure hemoglobin content. Sensitivity, specificity, negative predictive value, and false-negative value were estimated to test the instrument's accuracy; kappa coefficients were used to estimate inter- and intraobserver variability. Physician field evaluations of conjunctiva color for the screening of anemia, reported in the literature, have had sensitivities and specificities as high as 70%. Readings with the instrument demonstrated a 63% sensitivity, 72% specificity, and 38% false negatives for screening hemoglobin values of less than or equal to 13 g/dl. The interobserver kappa coefficients for three pairs of readers were good to excellent for the same hemoglobin screening value. Statistically significant differences were noted, however, between observers during the reliability test. The instrument can be used by unskilled personnel to improve their decision-making about whom to send for further care or for supplementation with iron.