Abstract
Synovasure has been designed and validated for use in the diagnosis of periprosthetic joint infection (PJI). It has a reported sensitivity of 97.4% (CI 86.1–99.6%) and specificity of 95.8% (CI 90.5–98.6%), higher than the variable results reported for aspiration by most units. At a cost of £500 per test, we aimed to establish cost-effectiveness and diagnostic accuracy, to determine its role in routine practice.
We developed a protocol for pre-operative aspiration or intra-operative use. Prerequisites for entry were a high index of clinical suspicion for PJI and equivocal standard investigations. All cases were discussed at the lower limb arthroplasty MDT and approved only if use would change clinical management.
Over 15 months, 36 tests were approved for 22 aspirations (5 hip, 17 knee) and 14 intra-operative cases (7 hip, 7 knee). 10/36 had undergone previous revision surgery. 35/36 cases complied with the protocol. All 22 Synovasure aspirations were negative, corresponding to the microbiology in all but one case; thought to be a contaminant. In the intra-operative group there was one true positive and 12 true negative tests, giving a sensitivity of 100% (95% CI 2.5–100%) and a specificity of 100% (95% CI 73.5–100%). Synovasure influenced decision making in 34/36 procedures. One test failed and in another there was evidence of frank infection. In 11 cases no surgery was performed versus a potential two-stage revision and in 21 cases a single rather than two-stage revision was performed. Resulting in estimated savings of £686,690, offset against a cost of £18,000.
The Synovasure test was found to be sensitive and specific and can aid decision-making particularly in complex cases with an equivocal diagnosis of PJI. The use of this test through a robust protocol driven peer review MDT process not only reduces patient morbidity but drives significant efficiency savings.
