Direct spectrophotometry of serum hemoglobin: an Allen correction compared with a three-wavelength polychromatic analysis.

An Allen correction and a polychromatic analysis are about equally effective in minimizing effects of interference by bilirubin and triglyceride turbidity in the direct spectrophotometry of serum hemoglobin: interference from bilirubin is nearly eliminated, that from turbidity substantially decreased. The limit of detectability of hemoglobin is 8 mg/L in the presence of a moderate concentration of bilirubin. A change in hemoglobin concentration as small as 16 mg/L can be detected in serum having a concentration near the upper limit of the reference interval, i.e., at the medical decision level. The polychromatic formula gives concentration estimates approximately 5% greater than those of the Allen correction. The formula for the Allen correction is hemoglobin (mg/L) = 1.68 mA415 - 0.84 mA380 - 0.84 mA450 . That for the polychromatic analysis is hemoglobin (mg/L) = 1.65 mA415 - 0.93 mA380 - 0.73 mA470 .