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

Abstract

SummaryReasons for performing study: Serum amyloid A (SAA) in synovial fluid has recently been used as a marker for septic arthritis in horses but the effects of repeated intra-articular (IA) administration of amikacin on synovial SAA concentrations are unknown. Objectives: To report the effect of repeated IA administration of amikacin on SAA, total protein (TP), nucleated cell count (NCC) and differential NCC in synovial fluid of healthy equine joints. Methods: A controlled, 2 period crossover study was performed on 5 clinically healthy horses. Each intercarpal joint received one of 2 treatments every 48 h for 5 consecutive times: arthrocentesis alone (control group) or arthrocentesis combined with IA administration of 500 mg of amikacin (treatment group). Clinical and lameness examinations were performed daily. Serum SAA and synovial SAA, TP, NCC and differential NCC were measured and statistically compared. Significance level was set at P<0.05. Results: Horses remained healthy and nonlame throughout the study. Baseline values for all variables were not significantly different between groups. Values for TP in the treatment group were significantly higher than in the control group after the first sample (P<0.05). In both groups NCC increased significantly (P<0.05) after the first sample. No significant changes were identified in differential NCC. In both groups, all synovial and most serum SAA concentrations remained below the lower limit of quantification. Conclusions: Repeated IA administration of amikacin caused increased values of TP and NCC in synovial fluid, with some TP concentrations falling within the range reported for septic arthritis. In contrast, synovial SAA concentrations did not increase in either group. Potential relevance: Synovial SAA could serve as a more reliable marker than TP and NCC when evaluating a joint previously sampled or treated with amikacin.

Effect of Arthroscopic Lavage on Systemic and Synovial Fluid Serum Amyloid A in Healthy Horses

“…Synovial fluid supernatant and serum were stored at −80°C for further SAA quantification. Quantification of systemic and synovial fluid SAA was performed using a human SAA turbidometric immunoassay (Eiken Chemical Co, Tokyo, Japan) previously validated for use in equine samples and used on previous studies on equine synovial fluid . Prior to quantification of SAA by an automated chemistry analyzer (F. Hoffmann‐La Roche Ltd, Basel, Switzerland), 10 μL of hyaluronidase (500 U/mL, H4272, Sigma‐Aldrich) was added to 490 μL of synovial fluid to reduce synovial fluid viscosity.…”

“…These values decreased promptly to undetectable values when clinical improvement was noticed. Moreover, synovial fluid SAA concentrations were not affected by either repeated arthrocentesis or repeated intra‐articular administration of amikacin . This suggests that synovial fluid SAA responds in different magnitude to inflammation than to sepsis, whereas the commonly used synovial fluid parameters total protein, nucleated cell count, and percentage of neutrophils may respond identically to nonseptic and septic inflammation.…”

“…Additionally, in a recent study performed in healthy joints, total protein peaked at 24 hours and nucleated cell counts reached values higher than 20 × 10 3 cells/µL at 12 hours after arthroscopic lavage with lactated Ringer's solution (LRS) . Furthermore, repeated arthrocentesis and repeated intra‐articular administration of amikacin every 48 hours caused an increase of total protein and nucleated cell counts to values in the range of septic arthritis . Currently, these are the only diagnostic methods available to the majority of equine practitioners, indicating the need for a new marker that is not affected by the high‐volume lavage used as part of the treatment for septic arthritis.…”

Factors Influencing Serum Amyloid Type A (Saa) Concentrations in Horses

“…SAA concentrations increased at 16 hours, reached a peak at 36 -48 h (227 times higher than the baseline), and remained elevated for two weeks. In complicated septic arthritis situations, SAA remains elevated both in serum and synovial fluid, so it can be used to monitor treatment effect, and that decreases simultaneously with the action of the treatment [22,54].…”

Can serum amyloid A concentrations aid diagnosis of synovial sepsis?

“…12 This means that treatment will not affect SAA concentrations and that the clinician will immediately be able to monitor response to treatment. SAA also has the potential to be used a monitoring and prognostic test, as hypothesised by Robinson and others 2017.…”