Breed predispositions, clinical findings, and prognostic factors for death in dogs with nonregenerative immune‐mediated anemia

Abstract

Background: Breed predispositions, survival, and prognostic factors have not been evaluated in dogs with nonregenerative immune-mediated anemia (nrIMA). Hypothesis/Objectives: To describe clinicopathologic variables, evaluate their associations with survival, and determine breed predispositions for dogs with nrIMA. Animals: Fifty-nine client-owned dogs with nrIMA. Methods: Referral hospital records were reviewed retrospectively for dogs with primary nrIMA (PCV ≤30%, corrected reticulocyte percentage (CR%) ≤1.0, bone marrow sampling with evidence of immune-mediated destruction, and underlying causes excluded). Breed predispositions were evaluated by calculation of odds ratios in a case control study; prognostic factors by logistic regression in a cohort study. Results: Fifty-nine dogs with nrIMA had a median PCV of 12% (interquartile range [IQR]: 10%-17%) and CR% 0.1 (0%-0.2%). At least ≥1 ACVIM IMHA diagnostic criteria were met by 35 dogs (59%). Whippets, Lurchers, and miniature Dachshunds were predisposed to nrIMA. Median survival time was 277 days (IQR: 37-1925), with 3-and 12-month survival rates 61% and 43%, respectively. Erythroid regeneration and remission were achieved by 88% and 62% of dogs, respectively. Corrected reticulocyte percentage >0.2 was associated with improved survival. Conclusion and Clinical Importance: Although there is overlap of clinical features between dogs with IMHA and nrIMA, the prognosis for those with nrIMA depends predominantly on the severity of reticulocytopenia.

Comparative study of immunohematological tests with canine blood samples submitted for a direct antiglobulin (Coombs’) test

“…Moreover, the 42 attending clinicians who responded reported that 70% of the DAT+ dogs with IMHA recovered or were clinically stable, while 30% of them died or were euthanized. These findings concur with prior outcome surveys [ 19 , 72 ]. Thus, while the results of the follow-up data are sparse in this as well as in prior studies [ 3 , 24 , 25 , 44 , 69 ], they support the value of monitoring dogs with IMHA during and after treatment.…”

“…Among the samples tested in this study, dogs with a positive DAT result had more frequent and more severe anemia (Hct < 18%) as was previously described [ 44 , 46 ], and the anemia was more likely regenerative in contrast to those in the DAT- group [ 19 , 25 , 43 ]. While there is no published study to directly compare our observations to, it is likely that some DAT- dogs had non-hemolytic anemias.…”

“…With respect to signalment, middle-aged and female dogs were overrepresented as reported in prior retrospective surveys [ 43 – 45 ], but there was neither an apparent breed predilection among dogs for which a DAT was requested nor for those with DAT+ results. In past studies the Cocker Spaniel was overrepresented [ 24 , 43 , 45 – 48 ], and a recent survey from the United Kingdom suggested a few other breeds with higher odd ratios for non-regenerative IMHA [ 19 ].…”

“…Similar to prior surveys of dogs with IMHA [ 25 , 43 , 44 ], not all DAT+ dogs showed evidence of erythroid regeneration. This may be due to pre-regenerative anemia (first 2–3 days of anemia), mild anemia, or inflammatory and necrotic processes associated with IMHA in dogs, leading to inhibition of adequate erythroid regeneration in the bone marrow [ 19 , 50 , 51 ]. Varied erythroid responses and bone marrow cytological and histological abnormalities have been documented in dogs with IMHA, but time-course was not evaluated [ 19 , 51 , 52 ].…”

“…It is the authors’ impression that the DAT is often skipped in the diagnostic approach of IMHA in dogs. Indeed, in a recent study of dogs suspected of having IMHA, only 20% were tested by DAT [ 19 ]. As such, a presumptive diagnosis of IMHA is frequently made without evidence of immune-mediated destruction of erythrocytes in anemic dogs [ 1 – 3 , 7 , 20 , 21 ].…”