Comparison of timing of relapse in dogs with nonassociative immune‐mediated hemolytic anemia, thrombocytopenia, or polyarthritis

Background Relapse is a clinical concern in dogs diagnosed with immune‐mediated hemolytic anemia (IMHA), thrombocytopenia (ITP), or polyarthritis (IMPA). The average time to relapse is unknown, and evidence that vaccination is associated with disease relapse is lacking. Hypothesis/Objectives Compare the incidence of relapse in groups of dogs with IMHA, ITP, or IMPA over a 24‐month period after diagnosis and compare proportions of dogs that received vaccines in those dogs that did and did not relapse. Animals One hundred sixty client‐owned dogs (73 with IMHA, 55 with ITP, 32 with IMPA). Methods Medical records of dogs were reviewed with the goal of following cases for a minimum of 2 years. Incidence of relapse was calculated for each disease, and relapse rates in dogs that were or were not vaccinated after diagnosis were compared. Results Relapse rates at 12 months differed significantly among disease groups (P = .02), with a higher rate for IMPA (35%) compared to IMHA (11%) or ITP (11%). Relapse rate at 24 months was 41% for IMPA, 18% for IMHA, and 23% for ITP. Ninety percent of IMPA relapses occurred in the first 12 months after diagnosis, compared with 56% for IMHA and 50% for ITP. Vaccine administration after diagnosis was not associated with relapse (P = .78). Conclusions and Clinical Importance Risk of disease relapse in IMPA is highest in the first year after diagnosis, with a higher relapse rate compared with IMHA and ITP. The role of vaccination in disease relapse remains unclear.