Measurement of carboxyhemoglobin and total hemoglobin by five specialized spectrophotometers (CO-oximeters) in comparison with reference methods

Abstract

We measured total hemoglobin (ctHb) and carboxyhemoglobin (COHb) in 100 patients' blood samples by using five specialized spectrophotometers (CO-oximeters) - IL 482 CO-Oximeter™ Corning 2500 CO-oximeter, Radiometer OSM™ 3 Hemoximeter™, Corning 270 CO-oximeter, and the AVL 912 CO-Oxylite™ - and compared the results with those obtained with the manual cyanmethemoglobin method and a gas-chromatographic (GC) method, respectively. For the ctHb measurements, the differences between the cyanmethemoglobin method and the CO-oximeters were not clinically important for any model. For the blood COHb measurements, the direction of the bias relative to GC was dependent on COHb concentration. In general, the CO-oximeters underestimated COHb concentration for COHb >2.5% of total hemoglobin but overestimated COHb concentration for COHb ≤2.5%. We conclude that all five CO-oximeters compared favorably with the reference methods for ctHb and for high concentrations of COHb. However, the inaccuracy of CO-oximeters for low-concentration (≤2.5%) COHb measurements may make these instruments unsuitable for some applications.