The normal hemoglobin (Hgb) is approximately 1/3 of the packed-cell volume (PCV) in mammals, and changes in this proportion can help characterize anemia. The same relationship is likely present in birds but has not been previously documented. A portable point-of-care hemoglobinometer was used in this study to calculate the Hgb concentration in avian blood samples to determine whether a proportional relationship exists between Hgb and PCV in birds. PCV values were determined using standard methods for birds. Blood samples were collected from 128 birds encompassing 13 avian orders and 33 species. A proportional, significant, and consistent relationship was identified between Hgb and PCV (Hgb = 0.304 × PCV + 0.461) in pooled samples. There were 8 or more blood samples in 9 orders, and there were no significant differences between 1 another or the pooled data. A different relationship was identified (Hgb = 0.217 × PCV + 6.692) for the order Phoenicopteriformes (American flamingo). The authors concluded that a simple relationship (Hgb [g/dL] = 0.30 × PCV) will provide a clinically reliable estimate of Hgb concentration from birds from the orders Anseriformes, Columbiformes, Falconiformes, Galliformes, Passeriformes, Psittaciformes, Sphenisciformes, and Strigiformes. However, a different relationship needs to be used for the order Phoenicopteriformes.

Commentary: Routine hematology is an important part of avian patient health assessment. Information gleaned from analysis of the erythron can assist in the diagnosis of anemia, infection, toxicosis, or other systemic disease. Avian hematology panels performed at most reference laboratories do not include Hgb concentration or calculated erythrocyte indices because of the nucleated nature of avian erythrocytes. These study results indicated that for all sampled orders the PCV can be used as a reliable estimate of Hgb concentration, and vice versa. Birds in the order Phoenicopteriformes (flamingos and their relatives) had a slightly different correlation than those in other orders; however, this is of little clinical significance to most practitioners. The additional advantage of the benchtop analyzer described in this study is the small volume of blood required for the test (less than a microhematocrit tube). The Hgb concentration could be used to estimate PCV in situations with only small available blood sample volumes. This study examined only clinically normal or acutely ill birds, and nearly all samples had PCV within reference ranges. Therefore, additional information may be required to validate the use of this method in cases of anemia or chronic illness.—Dominique Keller, DVM, PhD

Relationship of hemoglobin concentration to packed cell volume in avian blood samples. Velguth KE, Payton ME, Hoover JP. J AVIAN MED SURG 24:115-121, 2010.