Erythrocyte Sedimentation Rate Is a Promising Screening Test for Infections in Rehabilitated Birds.

Erythrocyte sedimentation rate (ESR) is a simple, inexpensive test that is an indirect measure of the acute-phase protein response to inflammation. Acute-phase assays can increase detection of illnesses when used in conjunction with other hematological tests, and may be more sensitive to some diseases than white blood cell counts. This study assessed the usefulness of testing ESR with a microhematocrit tube for detecting inflammatory and infectious conditions in rehabilitated birds. Values were measured in 119 clinically healthy birds from 5 orders, and differences between ages, orders, and healthy and unhealthy birds were compared. Cutoff values to differentiate clinically normal birds from those with trauma or infections were done by receiver operating characteristic curves, nonparametric methods, and a linear regression-based method to account for differences in packed cell volume (PCV). The ESRs of unhealthy birds (n = 188) were used to assess performance of the different cutoff methods. The receiver operating characteristic curve cutoffs for infected birds in Accipitriformes, in Strigiformes, and for combined orders had good sensitivity (78-97%), specificity (94-100%), and area under the curve values (0.913-0.990), but performance was likely overestimated due to sample size limitations. There was a significant negative correlation between PCV and ESR, but regression-based cutoffs had the worst overall performance, and all methods had low sensitivity for unhealthy passerines. Erythrocyte sedimentation rate appears to be a useful test in some orders, can be easily implemented, and can be performed with the same sample used to determine PCV and total protein, increasing diagnostic information without the need for additional blood or testing costs. However, species-, age-, and sex-specific differences must be further investigated to fully assess the usefulness of this test.