Relationship between the red blood cell distribution width (RDW) and erythrocyte values in anemic and non-anemic cats

Erythrocyte alterations require making decisions, guiding clinical conduct, determining prognoses, and choosing therapy options for diseases. Automated devices that can perform blood cell counts allow for calculation of amplitude distribution of erythrocytes red blood cell distribution width (RDW) and its fractions (RDW-CV and RDW-SD). It also evaluates quantitatively the heterogeneity of each erythrocyte, especially in the feline species where presence of anisocytosis is common, even under normal conditions. Contrary to human medicine where there has been universal acceptance of RDW, there are only a handful of veterinarians and laboratories that currently use this parameter as a diagnostic tool for differential laboratory diagnosis of anemia in veterinary medicine, possibly owing to unfamiliarity with the application. Faced with limited availability of information in scientific literature regarding RDW values for the domestic cat, this study aimed to associate RDW values with erythrocytes, hematocrit, hemoglobin, and mean corpuscular volume (MCV) in 407 adult cats of no defined pedigree (n = 218 males and n = 189 females; 335 non-anemic and 72 anemic). In the present study, RDW-SD values in anemic cats were 20.4% above those considered normal, while RDW-CV values were 25.2% higher than those considered normal for the species. We concluded that interpretation of RDW values is an important tool for evaluating heterogeneity of erythrocytes with regard to anemia. Even in non-anemic animals, increased levels of RDW may suggest early erythrocyte alterations.