Whole-blood hemoglobin determinations: a comparison of methodologies.

The Coulter Model S provides an accurate measurement of total hemoglobin (Hb) content in peripheral blood even when elevated levels of carboxyhemoglobin (HbCO) are present. Commercial standards and diluents for spectrophotometric determinations of cyanmethemoglobin (HiCN) are variable in quality. All diluents studied produce turbidity in some samples, and this may explain why manual Hb determinations tend to be higher than hemoglobin measurement on the Coulter S. The most reliable diluent was the reagent described by Van Kampen and Zijlstra. Its reliability is enhanced by centrifugation of sample in diluent. The use of a narrow-band-pass spectrophotometer for routine HiCN determinations in a clinical laboratory is not recommended because of its sensitivity to turbidity and HbCO.