Color, distribution, and method limits

Hypochromia means increased central pallor from reduced hemoglobinization. A target cell has a central hemoglobinized area, a pale zone, and a peripheral hemoglobinized rim, so it is not simply hypochromia. MCHC is a calculated whole-sample index, not a direct visual measure of color; a low aggregate MCHC supports hypochromia somewhere in the population, not specifically in the microcytic group.

Polychromasia on a Romanowsky-stained film reflects residual RNA in young red cells. It is a qualitative surrogate for reticulocytes, not a numeric reticulocyte measurement. In this case, 2.8% reticulocytes is only concordant with polychromasia; without an absolute reticulocyte count and reporting convention it does not establish the magnitude of marrow response. A broad or bimodal RBC-volume histogram is analyzer evidence that needs film correlation.

Review an abnormal histogram first as a volume-distribution signal: assess peak alignment, shoulders, broadening, and film correlation. Keep cold-agglutination review separate: irregular clumps, implausibly high MCHC, and a method-appropriate abnormal pattern require specimen and original-film review followed by a locally validated warmed-specimen process.