Abstract
BackgroundSynovial fluid culture is the standard investigation for the preoperative diagnosis of periprosthetic joint infection (PJI). However, the culture has limited sensitivity and requires several days until result. We evaluated the value of isothermal microcalorimetry for real-time diagnosis of PJI based on heat produced by microbial growth in synovial fluid.MethodsPatients undergoing aspiration of prosthetic hip or knee joint before revision surgery were prospectively included between 2014 and 2015. The performance of microcalorimetry was compared to synovial fluid culture using McNemar’s chi-squared test. Pearson’s correlation coefficient was calculated for synovial fluid leukocyte count and microcalorimetric heat.ResultsOf 107 included patients (58 knee and 49 hip prosthesis), PJI was diagnosed in 46 patients (43%) and aseptic failure in 61 patients (57%) according to institutional criteria. In 26 PJI cases (56%) the pathogen grew in synovial fluid and intra-operative cultures. The sensitivity of synovial fluid culture and microcalorimetry was both 39% and the results were concordant in 98 patients (92%). In patients with PJI, microcalorimetry missed 4 pathogens which grew in synovial fluid culture, whereas culture missed 4 pathogens detected by microcalorimetry. A linear correlation (r = 0.366) was found between leukocyte count and microcalorimetric heat in synovial fluid (p < 0.001). The median time to positivity of microcalorimetry was 9 h (range, 1–64 h) vs. 3 days for cultures (range, 1–14 days).ConclusionMicrocalorimetry of synovial fluid allows thermogenic diagnosis of periprosthetic joint infection in synovial fluid. The diagnostic performance of synovial fluid microcalorimetry is comparable to culture and delivers results considerably faster.Trial registrationThis prospective study was registered on August 21, 2015 with the public clinical trial identification NCT02530229.
Highlights
Synovial fluid culture is the standard investigation for the preoperative diagnosis of periprosthetic joint infection (PJI)
An increasing number of new diagnostic methods for fast and reliable diagnosis of infection are being investigated to overcome the limitations of microbial cultures, such as synovial fluid leukocyte count [4], multiplex polymerase chain reaction (PCR) [5], leukocyte esterase [6], alpha-defensin [7,8,9,10] and generation sequencing [11, 12]
Study definitions At least one of the following criteria were necessary for diagnosing PJI, as used in other studies [5, 9, 10, 17,18,19]: (i) visual identification of macroscopic purulence around the prosthesis, (ii) a visible sinus tract, (iii) an elevated synovial fluid leukocyte count (> 2000 leukocytes/μl) or differential (> 70% granulocytes) [3, 4], (iv) positive culture of synovial fluid, periprosthetic tissue or culture of sonication, (v) histopathologic inflammation with ≥2 granulocytes per high-power field in periprosthetic tissue
Summary
Synovial fluid culture is the standard investigation for the preoperative diagnosis of periprosthetic joint infection (PJI). An increasing number of new diagnostic methods for fast and reliable diagnosis of infection are being investigated to overcome the limitations of microbial cultures, such as synovial fluid leukocyte count [4], multiplex polymerase chain reaction (PCR) [5], leukocyte esterase [6], alpha-defensin [7,8,9,10] and generation sequencing [11, 12] These tests have limitations including technical complexity, long processing time, insufficient sensitivity or specificity and inability to identify the causing pathogen. Microcalorimetry of sonication fluid was useful in diagnosing PJI [16] with a considerably faster detection time (6 h) than conventional microbial cultures
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