Case-control study of plasma mean platelet component concentration and survival analysis for dogs with immune-mediated hemolytic anemia.

OBJECTIVE To determine whether dogs with immune-mediated hemolytic anemia (IMHA) had a low plasma mean platelet component (MPC) concentration and whether MPC was associated with outcome. DESIGN Retrospective case-control study and survival analysis. ANIMALS 95 dogs with IMHA (cases) as well as 95 healthy dogs and 95 sick dogs without IMHA (controls) matched to cases by age, reproductive status, and breed. PROCEDURES Plasma MPC concentration at initial examination was compared among groups. For dogs with IMHA only, sex, age, serum urea and bilirubin concentrations, Hct, platelet count, and plasma fibrinogen, D-dimer, and MPC concentrations were evaluated for associations with survival to 42 days after initial examination. RESULTS Plasma MPC concentration was significantly lower in dogs with IMHA than in the other 2 dog groups. In dogs with IMHA, plasma MPC concentration was the only factor significantly associated with outcome. The optimal plasma MPC concentration cutoff value for predicting nonsurvival of dogs with IMHA was 19.1 g/dL; values ≤ 19.1 g/dL were associated with nonsurvival. Likewise, the survival curve for dogs with plasma MPC concentrations ≤ 19.1 g/dL differed significantly from that for dogs with values > 19.1 g/dL. The mean estimated risk of death for dogs with IMHA decreased by 16% for every unit increase in plasma MPC concentration. CONCLUSIONS AND CLINICAL RELEVANCE In dogs with IMHA, platelets appeared to have been activated to a greater degree, as determined by lower plasma MPC concentrations, than in healthy dogs or sick dogs without IMHA. Plasma MPC concentration at initial examination may be useful for predicting prognosis in dogs with IMHA.