IMHA: Which Regimen Works Best

Immune-mediated hemolytic anemia (IMHA) is a type II autoimmune response directed at antigens expressed on the surface of red blood cells. A variety of immunosuppressive agents are used in IMHA treatment; however, evidence for the effectiveness of specific drugs or proper combinations of drugs is lacking. This study evaluated 42 dogs that were treated for IMHA but for which no clinical underlying cause could be found. All except 5 dogs received 1 of 3 immunosuppressive treatment regimens: prednisolone and cyclosporine (n = 17), prednisolone and azathioprine (n = 9), or prednisolone alone (n = 11). The remaining 5 dogs received all 3 or different combinations of drugs, but group sizes were too small for inclusion. Azathioprine and cyclosporine were given at median dose rates of 1.8 mg/kg PO Q 24 H (range, 1.3–2.7 mg/kg) and 5.0 mg/kg PO Q 24 H (range, 3.0–8.0 mg/kg), respectively. Daily dose rates for prednisolone varied between the treatment groups, with ranges of 1.0 to 4.0 mg/kg PO Q 24 H. Adjunctive therapies included transfusions of whole blood or packed red blood cells, gastroprotectants, GI promotility drugs, heparin, and low-dose aspirin. Two dogs also received single injections of cyclophosphamide and 4 dogs received human g-globulin. No dog received both cyclophosphamide and human g-globulin.

Mortality rates between groups suggested that treatment regimens had a significant effect on the outcome of cases. The apparent difference in mortality may have been affected by doses of immunosuppressive treatment regimens as well as adjunctive treatments. Overall, the small sample sizes made direct correlations difficult. Increased serum bilirubin and serum urea values were noted to be negative prognostic indicators.

Commentary: This study attempted to evaluate three treatment regimens for IMHA. In my opinion, limitations due to its retrospective nature, small sample size, and treatment variability (eg, dosing) rendered it inadequate. Also, while the degree of elevation in bilirubin and urea was statistically significant, it did not appear to be clinically significant; this information should not be used as a negative prognostic factor nor should patients be condemned based on mild elevation in these values. Lastly, the use of low-dose aspirin to prevent pulmonary thromboembolism is generally considered a standard of care with IMHA patients but was not adequately evaluated in this study. A benefit of the study was the finding that higher doses of prednisolone (>2 mg/kg Q 24 H) may not be necessary and that using an appropriate yet effective dose may help minimize adverse events.—Justine A. Lee, DVM, DACVECC, DABT

Evaluation of immunosuppressive regimens for immune-mediated haemolytic anaemia: A retrospective study of 42 dogs. Swann JW, Skelly BJ. J SMALL ANIM PRACT 52:353-358, 2011.