Can a Stall-Side Test Confirm Synovial Structure Infections?

Using one stall-side SAA test to evaluate synovial fluids can be a useful adjunct to diagnosis, researchers found.

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Infected joint structures are serious business. They have the potential to end not only a horse’s athletic career but also his life—these cases have a mortality rate of 10-50%. But confirming infection and its cause for pursuing proper treatment can be costly and time-consuming. Veterinarians have been exploring the accuracy of a speedier approach, looking at serum amyloid A (SAA) levels.

The liver and joint synovial membranes produce the acute-phase protein SAA in response to pro-inflammatory mediators, and veterinarians have been examining SAA levels for detecting a number of equine conditions. Florent David, DVM, MSc, Dipl. ACVS, ECVS, ACVSMR, ECVDI, of Mid-Atlantic Equine Medical Center, in New Jersey, recently evaluated SAA levels in inflamed, septic (infected) joints versus inflamed, non-septic joints, and presented his study findings at the 2015 American Association of Equine Practitioner’s Convention, held Dec. 5-9 in Las Vegas.

The current gold standard for joint infection diagnosis is bacterial culture and sensitivity of a synovial (joint) fluid sample. At least 48-72 critical hours can pass between taking the sample and obtaining definitive results. Other methods, ranging from cytology (examination of cell types) to look for white blood cells indicative of infection to palpation/pressure testing, aren’t foolproof in differentiating between simple inflammation and potentially life-threatening septic conditions.

David’s study included 62 horses with 72 synovial fluid samples (some horses had more than one affected synovial structure). The horses had a history of clinical signs of inflammation, and some horses were treated with anti-inflammatory and antimicrobial medications prior to referral. In both categories–inflamed septic and inflamed but non-septic–about two-thirds of the affected structures were joints and one-third were synovial sheaths (sheath covering a tendon) and bursae (a fluid-filled sac around a tendon to counter friction around a joint. Most of the horses were lame at the walk

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Written by:

Nancy S. Loving, DVM, owns Loving Equine Clinic in Boulder, Colorado, and has a special interest in managing the care of sport horses. Her book, All Horse Systems Go, is a comprehensive veterinary care and conditioning resource in full color that covers all facets of horse care. She has also authored the books Go the Distance as a resource for endurance horse owners, Conformation and Performance, and First Aid for Horse and Rider in addition to many veterinary articles for both horse owner and professional audiences.

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