Synovasure 'quick test' is not as accurate as the laboratory-based α-defensin immunoassay: a systematic review and meta-analysis.

AIMS: α-defensin is a biomarker which has been described as having a high degree of accuracy in the diagnosis of periprosthetic joint infection (PJI). Current meta-analyses are based on the α-defensin laboratory-based immunoassay rather than the quick on-table lateral flow test kit. This study is the first meta-analysis to compare the accuracy of the α-defensin laboratory-based immunoassay and the lateral flow test kit for the diagnosis of PJI.

MATERIALS AND METHODS: A systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Inclusion criteria were all clinical studies where the diagnosis of PJI was uncertain. All studies selected used the Musculoskeletal Infection Society (MSIS) or modified MSIS criteria. Two independent reviewers reviewed the studies and extracted data. A meta-analysis of results was carried out: pooled sensitivity, specificity, positive and negative likelihood ratio, heterogeneity and areas under curves are reported.

RESULTS: Ten studies (759 patients) were included. Of these, seven studies (640 patients) evaluated the laboratory-based α-defensin immunoassay and three (119 patients) the lateral flow test. The pooled sensitivity and specificity of the qualitative α-defensin laboratory immunoassay was 0.953 (95% confidence interval (CI) 0.87 to 0.984) and 0.965 (95% CI 0.943 to 0.979) respectively. The pooled positive likelihood ratio (PLR) and negative likelihood ratio (NLR) were 34.86 (95% CI 19.34 to 62.85) and 0.02 (95% CI 0.00 to 0.11). The pooled sensitivity and specificity of the lateral flow test were 0.774 (95% CI 0.637 to 0.870) and 0.913 (95% CI 0.828 to 0.958), respectively. The pooled PLR and NLR were 8.675 (95% CI 4.229 to 17.794) and 0.248 (95% CI 0.147 to 0.418), respectively.

CONCLUSION: The pooled sensitivity and specificity of the lateral flow test were lower than those of the α-defensin laboratory-based immunoassay test. Hence, care must be taken with interpretation of the lateral flow test when relying on its results for the intra-operative diagnosis of PJI. Cite this article: Bone Joint J 2018;100-B:66-72.