Protease activity as a prognostic factor for wound healing in complex wounds.

Healing mechanisms are disrupted in complex wounds. Proteases may persist longer in non-healing wounds. We sought to investigate whether protease activity, protease inhibitor activity or their combinations are independent prognostic factors for healing of complex wounds. We searched MEDLINE, EMBASE, CINAHL and The Cochrane Library to March 2019. Study selection comprised longitudinal studies assessing the independent effect of proteases, their inhibitors or ratios of the two, on healing of complex wounds, whilst controlling for confounding factors. Two reviewers independently extracted data and assessed risk of bias. We conducted meta-analyses separately for proteases, inhibitors and ratios. We graded the evidence certainty (quality). We identified eight eligible studies in 10 cohorts involving 343 participants. Risk of bias was moderate or high. Elevated protease activity may be associated with less wound healing (Standardised Mean Difference [SMD]: -0.41, 95% CI -0.72 to -0.11; nine cohorts); and elevated protease inhibitor activity with more healing (SMD: 0.37, 95% CI 0.06 to 0.68; five cohorts), this is low certainty evidence. Increased protease:inhibitor ratios may be associated with less healing (SMD -0.47, 95% CI -0.94 to -0.01; four cohorts), but this evidence is of very low certainty. Heterogeneity in protease activity was unexplained by pre-specified subgroup analyses for wound type or protease activity status, but partially explained by protease class. Post-hoc analysis suggested elevated levels of a particular protease, MMP-1, may be associated with more healing and other proteases with less healing. This is low/very low certainty evidence. Limitations were small included studies at moderate or high risk of bias, and the use of post-hoc analyses. Conclusions: elevated protease activity and protease:inhibitor ratios may be associated with less healing, and elevated inhibitor levels with more healing. There may be important differences between MMP-1 and other proteases. High quality research is needed to explore these new findings further. This article is protected by copyright. All rights reserved.