CAMLPR Hematology Practice Test

Hemoglobin is measured colorimetrically by converting all Hb in the sample to a stable cyanmethemoglobin pigment and then measuring its color intensity. This conversion uses Drabkin’s reagent, which contains ferricyanide and cyanide; Hb released from red cells is oxidized and forms cyanmethemoglobin. The resulting pigment has a strong, stable color whose absorbance is proportional to the Hb amount in the sample, in line with Beer-Lambert law. The absorbance is read with a spectrophotometer at about 525–540 nm, and a reagent blank is subtracted to account for any color from the reagents themselves. This setup provides a wide linear range and reliable results across common sample conditions, which is why it’s the standard method. Other options don’t fit because they describe different approaches or wavelengths not normally used for total Hb quantification with this well-established method.