Measurement of synovial fluid and serum concentrations of the 846 epitope of chondroitin sulfate and of carboxy propeptides of type II procollagen for diagnosis of osteochondral fragmentation in horses

Objective-To determine whether serum or synovial fluid concentrations of ch ondroitin sulfate epitope 846 and carboxy propeptides of type II collagen ( CPII) can be used to diagnose osteochondral fragmentation (OC)in horses. Animals-38 horses with unilateral OC of the radiocarpal (n = 31) or interca rpal (33) joints and 8 clinically and radiographically normal horses. Procedures-For horses with OC, serum and synovial fluid concentrations of e pitope 846, CPII, and keratan sulfate (KS) were determined, along with syno vial fluid WBC counts and total protein concentrations. Serum epitope 846, CPII, and KS concentrations were measured in control horses. Results-Synovial fluid epitope 846 and total protein concentrations were si gnificantly higher in the joints with OC than in unaffected joints, but CPI I and KS concentrations and WBC counts were not. Synovial fluid total prote in and 846 epitope concentrations were linearly related to grade of OC. Ser um epitope 846 and CPII concentrations were significantly higher in horses with OC than in control horses. Discriminant analysis allowed 27 of 34 (79% ) horses to be correctly classified as having or not having OC on the basis of serum epitope 846 and CPII concentrations. Conclusions-Results suggest that serum and synovial fluid concentrations of epitope 846 and CPII are associated with OC, Increases in concentrations o f epitope 846 and CPII suggest that increased synthesis of cartilage aggrec an and type II procollagen may be associated with OC. Clinical Relevance-Measurement of serum epitope 846 and CPII concentrations may be useful in the diagnosis of OC in horses.