Dynamics in serum of the inflammatory markers serum amyloid A (SAA), haptoglobin, fibrinogen and alpha2-globulins during induced noninfectious arthritis in the horse.
Authors: Hultén C, Grönlund U, Hirvonen J, Tulamo R-M, Suominen M M, Marhaug G, Forsberg M
Journal: Equine veterinary journal
Summary
# Editorial Summary Noninfectious joint inflammation is clinically significant in equine practice, yet the systemic inflammatory response it triggers remains poorly characterised; this study investigated whether experimentally induced sterile arthritis would generate measurable acute phase protein (APP) responses in serum. Twenty-four healthy Standardbred horses received aseptic amphotericin B injections into the midcarpal joint, with serum sampling conducted from baseline through to day 15 post-induction, measuring serum amyloid A (SAA), haptoglobin, fibrinogen and alpha2-globulins alongside clinical signs of lameness, effusion and systemic changes. All horses mounted a substantial systemic inflammatory response despite the localised, noninfectious nature of the insult: SAA showed the most dramatic elevation (227-fold at 36–48 hours), haptoglobin increased 1.14-fold by 48–96 hours, fibrinogen rose 0.87-fold between 36–72 hours, and alpha2-globulins showed modest increases of 0.55-fold, with all markers returning to baseline by day 15. These findings carry important diagnostic implications—elevated APP concentrations need not indicate infectious arthritis, requiring practitioners to integrate clinical, imaging and potentially synovial fluid findings when distinguishing between septic and noninfectious joint disease, whilst suggesting that APP monitoring may have limited utility in tracking chronic noninfectious arthritis progression.
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Practical Takeaways
- •Elevated serum acute phase proteins (particularly SAA) in a horse with arthritis cannot be used alone to differentiate infectious from noninfectious joint disease—clinical, radiological and joint fluid analysis remain essential for diagnosis
- •Systemic inflammatory signs (fever, tachycardia, tachypnea) and lameness from noninfectious arthritis typically resolve within 24-48 hours, helping distinguish this condition from systemic infection
- •When interpreting bloodwork in arthritic horses, consider that SAA elevation can persist for 2 weeks even with uncomplicated noninfectious joint inflammation
Key Findings
- •SAA concentrations increased 227 times baseline by 36-48 hours post-induction of noninfectious arthritis
- •Haptoglobin increased 1.14 times baseline, peaking at 48-96 hours post-induction
- •Fibrinogen and alpha2-globulins showed minor increases (0.87 and 0.55 times baseline respectively) and all acute phase markers returned to baseline by Day 15
- •Single-joint noninfectious arthritis induces measurable systemic acute phase response, indicating elevated acute phase proteins do not necessarily indicate infectious arthritis