Which hemoglobin form will NOT be measured by the cyanmethemoglobin method?

The cyanmethemoglobin method is a widely used laboratory technique for measuring the concentration of hemoglobin in blood. This method primarily converts different forms of hemoglobin into cyanmethemoglobin, which can then be quantified spectrophotometrically. However, not all forms of hemoglobin react in the same way.

Sulfhemoglobin is a stable compound formed when sulfur is incorporated into the hemoglobin molecule. This unique modification is not reduced or converted into cyanmethemoglobin during the testing process, making it undetectable by this method. Consequently, it remains unmeasured, which is why it is the correct answer to the question.

In contrast, other forms of hemoglobin, such as carboxyhemoglobin, methemoglobin, and oxyhemoglobin, can be converted and measured using this method, as they can be oxidized or react with the reagents present in the cyanmethemoglobin assay. This is critical for differentiating the various types of hemoglobin and accurately assessing oxygen transport capacity in patients.