Serum, synovial IL-6 predicts prosthetic joint injuries
Levels of interleukin (IL)-6 in the synovial fluid has significant diagnostic value for prosthetic joint injuries (PJI), especially in periprosthetic infections in the hip and knee, reports a new meta-analysis. Moreover, serum IL-6, although less sensitive, has high specificity and may also help diagnose prosthetic failure.
Studies that diagnosed PJI using serum and synovial IL-6 levels were searched from the databases of Medline and Embase. Only those with study sample sizes >10 and that indicated the date of serum and synovial fluid collection and assessment were included.
The study design, number and characteristics of patients, location of the operation, reference standards and other similar information were extracted from the selected studies. The quality assessment of studies of diagnostic accuracy included in systematic reviews (QUADAS) tool was used to evaluate the methodological quality of selected studies.
After applying the selection criteria, a total of 17 studies were included in the present meta-analysis; all were prospective studies. Of these, nine, six and two studies evaluated the diagnostic value of serum IL-6, synovial IL-6 and both, respectively, for PJI. QUADAS showed that quality was moderate to high. [Sci Rep 2017;7:1496]
For the diagnosis of PJI, serum levels of IL-6 had a pooled sensitivity of 0.72 (95 percent CI, 0.63 to 0.80) and a pooled specificity of 0.89 (0.77 to 0.95). On the other hand, the pooled diagnostic odds ratio (DOR) and area under the curve (AUC) for serum IL-6 levels were 20 (7 to 58) and 0.83 (0.79 to 0.86), respectively.
Moreover, the positive and negative likelihood ratios (PLR and NLR, respectively) for the diagnosis of PJI using serum IL-6 were 6.4 (2.9 to 14.1) and 0.31 (0.22 to 0.44), respectively.
Synovial fluid IL-6 levels had a pooled sensitivity of 0.91 (0.82 to 0.96) and a pooled specificity of 0.90 (0.84 to 0.95) for the diagnosis of PJI. The corresponding DOR and AUC values were 101 (28 to 358) and 0.96 (0.9 to 0.98), respectively.
Similarly, the PLR and NLR for using synovial fluid IL-6 levels to diagnose PJI were 9.5 (5.3 to 17.2) and 0.09 (0.04 to 0.21), respectively. Post-test probabilities of PJI for serum and synovial fluid IL-6 were 7 and 2 percent, respectively.
The current gold standard for diagnosing PJI is periprosthetic tissue culture, the investigators wrote. Its accuracy and value can be improved by polymerase chain reaction and sonication. However, all these techniques cannot be performed prior to revision surgery.
Nuclear medicine techniques are also well-established methods of diagnosing PJI, each with their corresponding high specificities and sensitivities. However, the high cost and exposure to radiation is a barrier to its consistent use.
Because of its involvement in inflammation and various immune responses, IL-6 was a well-suited candidate for the marker selection for PJI. Indeed, while some discrepancies about its degree of diagnostic value, especially in the serum, the general consensus is that IL-6, particularly in the synovial fluid, may potentially be a powerful marker for PJI, the investigators wrote.
“The present meta-analysis indicated that abnormally high synovial fluid IL-6 level is a strong indicator of PJI, with an AUC of 0.96.”
“The current meta-analysis indicated that synovial fluid IL-6 can be used for the diagnosis of PJI after joint arthroplasty. Although serum IL-6 is less sensitive than synovial fluid IL-6, it is one of the best serum biomarkers for PJI detection,” the investigators said
“Because of its reliable post-test probability, serum IL-6 assessment should be included as a regular test for patients with prosthetic failure,” they added.