UK–Ireland Study Questions Routine Screening in Dogs With Immune‐Mediated Hemolytic Anemia

Multicenter, Retrospective Determination of the Clinical Utility of Screening Tests in Dogs With Immune-Mediated Hemolytic Anemia in the United Kingdom and Ireland

Tyler Morrison, Ioannis L. Oikonomidis, Hannah K. Walker, Nuno Sousa Santos, Sophie A. Conway, Benoît Cuq, Carolina S. C. Albuquerque, Claudia Gil-Morales, Glynn Woods

Background

Immune‐mediated hemolytic anemia (IMHA) is a common and severe disease in dogs, often prompting extensive diagnostic screening to identify potential triggers such as infection, neoplasia, or inflammation. While screening can uncover concurrent diseases, the frequency and clinical significance of such findings are unclear, particularly in the United Kingdom and Ireland where infectious disease prevalence is low. This study aimed to assess how often IMHA in dogs is associative (linked to a concurrent condition) versus non-associative (primary or cryptogenic) and to determine the practical value of routine diagnostic screening.

Methods

A retrospective multicenter cohort study was conducted using records from five referral hospitals across the UK and Ireland between 2018 and 2022. A total of 222 client-owned dogs with confirmed IMHA, as defined by ACVIM consensus criteria, were included. All cases underwent mandatory thoracic and abdominal imaging, and further testing—such as urinalysis, infectious disease screening, and cytology—was performed when clinically indicated. Findings were categorized as associative, incidental, or non-associative. Statistical analyses, including multivariable logistic regression, were used to identify predictors of associative IMHA.

Results

Associative IMHA was diagnosed in 73 of 222 dogs (33%). Of these, 24 cases (11%) were attributed to toxic or drug exposure, 17 (8%) to infectious diseases, 16 (7%) to neoplasia, and 13 (6%) to noninfectious inflammatory conditions. The remaining 149 dogs (67%) had either incidental findings (46%) or no pertinent abnormalities (21%). Older age was the only significant predictor of associative IMHA (odds ratio 1.108 per year; 95% CI 1.012–1.218; p = 0.03). Common imaging findings included hepatosplenomegaly, parenchymal changes, or mild effusions, most deemed unrelated to IMHA. Only a small fraction of findings directly altered case management. Infectious disease positivity was rare, with just two confirmed cases (Ehrlichia spp. and Angiostrongylus vasorum).

Limitations

The retrospective design and variation in diagnostic protocols among centers may have influenced results. Some dogs lacked comprehensive testing (e.g., infectious disease PCR or histopathology), and cytology was underutilized relative to prior studies. The classification of “associative” versus “incidental” relied on retrospective clinical judgment, and some true secondary causes may have gone undetected. The study population reflected referral-level cases and may not generalize to primary care.

Conclusions

Roughly one-third of dogs with IMHA in the UK and Ireland have an identifiable concurrent condition, but the diagnostic yield of extensive routine screening is limited. Older dogs were more likely to show associative findings, suggesting age-guided, rather than blanket, diagnostic screening may improve efficiency and cost-effectiveness. Although comprehensive workups remain justified when notable findings emerge, routine exhaustive testing for all IMHA cases appears of limited benefit in low-infectious-disease regions.

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