A simple method for measuring fetal hemoglobin by co-oximetry

A simple, rapid method is presented for assessing the fetal hemoglobin fraction (%HbF). The principle of the measurement is straightforward. If two co-oximeters differ in the extent to which fetal hemoglobin interferes with their measurements of a particular analyte and if no other source of interference is present, then the magnitude of the difference in the HbF-induced interference between the two instruments can provide a quantitative measure of the fetal hemoglobin fraction. The present method does not require measuring optical absorbances at specific wavelengths or solving multiple simultaneous equations. On the contrary, the present method requires only one measurement on each instrument and a single simple calculation that yields a useful estimation of %HbF. Finally, it should be noted that this method can also be used for quantifying the concentrations of other compounds if two co-oximeters are available that differ appreciably in the extent to which the compound of interest interferes with their measurements of a particular analyte.