Objectives: To provide a description of primary idiopathic immune-mediated polyarthritis, including longterm outcome and relapse rates, for dogs starting treatment with corticosteroids alone or corticosteroids with a second immunosuppressant.Materials and MethOds: Medical records were reviewed between January 2012 and December 2017 to identify dogs diagnosed with primary immune-mediated polyarthritis. Data including signalment, clinicopathological findings, type and duration of treatment, relapse and outcome were recorded.results: Seventy-three dogs were included. Fifty-four dogs were started on corticosteroid monotherapy (an additional immunosuppressant was introduced later in 27/54 dogs) and 19 dogs were treated with multi-modal immunosuppression from the outset. Ninety-five percent (69/73) of dogs responded favourably to therapy although death was attributed to immune-mediated polyarthritis in 19% (14/73) of dogs. Relapse of clinical signs was reported in 53% (39/73) dogs (31/39 while on treatment), with multiple relapses observed in 17 dogs. Complete cure (permanent withdrawal of immunosuppressive medication) was achieved in 46 dogs (63%). Overall, 81% of dogs had a well-managed disease for an extended timeframe (≥1131 days). Fourteen of 19 (74%) dogs that started treatment with multi-modal immunosuppression and 32 of 54 (59%) started on corticosteroids alone achieved a complete cure.clinical significance: This study provides extended follow-up information for a large cohort of dogs with primary immune-mediated polyarthritis. Immunosuppressive therapy was discontinued in the majority of dogs but disease-associated mortality remains high.

Objective To assess platelet storage lesion development as evaluated by measurement of metabolic markers, platelet activation markers, and aggregometry, and determine the occurrence of bacterial growth in platelets stored in platelet additive solution (PAS) at 4°C for 7 days. Design Prospective, ex vivo experimental controlled study. Setting Research laboratory of a university veterinary teaching hospital. Animals Ten units of canine platelet concentrate collected from blood bank donations. Interventions Concentrates were aliquoted into 4 separate bags containing 100% plasma (control) or 30% plasma and 70% of a PAS (Plasma‐Lyte A, Isoplate, or InterSol). Samples were stored at 4°C without agitation. At days 0, 3, 5, and 7, samples were analyzed for platelet count, mean platelet volume, glucose, lactate, lactate dehydrogenase, Po2, Pco2, degree of swirling, aggregate formation, aggregation via light aggregometry, surface P‐selectin via flow cytometry, and bacterial contamination via culture. Measurements and Main Results Development of storage lesions was minimal, demonstrated by maintenance of a mean pH > 7.2 and mean lactate values <6 mmol/L at day 7 in all solutions. Glucose utilization did not vary significantly between any of the solutions. No significant difference was found between plasma and PAS for Po2 and Pco2. P‐selectin expression measured via flow cytometry showed a low platelet activation percent in all the solutions. InterSol had the lowest mean maximum percent aggregation (P < 0.001) and Isoplate the highest (P < 0.05). The mean maximum percent aggregation increased between day 0 and day 7 in all solutions. No bacterial growth was found in any of the solutions. Conclusions Overall, PASs were comparable to plasma for the cold storage of platelets. Cold‐stored platelets showed minimal storage lesion development with no bacterial growth. Plasma‐, Plasma‐Lyte A‐, and Isoplate‐stored platelets maintained function for up to 7 days at 4°C.