Effect of repeated intra-articular administration of amikacin on serum amyloid A concentration, total protein and nucleated cell count in synovial fluid from healthy horses

Abstract

Introduction: Serum amyloid A (SAA) in synovial fluid has recently been used as a marker for septic arthritis in horses. The objective of this study was to report the effect of intraarticular administration of amikacin on 1) SAA; total protein (TP), nucleated cell count (NCC) and differential nucleated cell count (DNCC) in the synovial fluid of equine healthy joints, and 2) SAA concentration in systemic blood. Material and Methods: A prospective, two-period, cross-over study was performed using 6 horses determined to be healthy based on clinical, lameness and haematological examinations. Each horse’s intercarpal joint received one of two treatments: repeated arthrocentesis (CG) or repeated arthrocentesis and intra-articular administration of 500 mg of amikacin sulphate (TG). Arthrocenteses, and synovial fluid and systemic blood sample collections were performed every 48h (baseline, 48, 96, 144 and 192h). Systemic SAA and synovial SAA, TP, NCC and DNCC were measured in all samples. Clinical and lameness examinations were performed daily. A 20-day washout was allowed between treatments. Treatments were compared using cross-over ANOVA, Student T and MannWhitney U tests. Significance level was set at p<0.05. Results: Horses did not show lameness throughout the study. One horse was excluded from the study due to unrelated respiratory disease. Serum amyloid A concentrations in serum and synovial fluid did not vary during the study in either group and remained below the lower limit of quantification. Baseline values for TP, NCC and DNCC were not statistically different between groups. Total protein values for TG were significantly higher than for CG after the first sample (p<0.05). In both groups NCC increased significantly (p<0.05) after the first sample but values remained within normal ranges throughout the study. No significant changes were found in DNCC. Conclusion: Repeated arthrocentesis alone or in combination with intra-articular amikacin did not affect systemic or synovial SAA concentrations in healthy horses. In contrast, synovial TP and NCC values increased over time; some of the TP values observed were within the range reported for septic arthritis. Synovial SAA could serve as a more reliable marker than TP and NCC when evaluating the clinical progression of a joint that has being treated with repeated intra-articular administration of amikacin. Copyright