Protease activity as a prognostic factor for wound healing in venous leg ulcers

BACKGROUND

Venous leg ulcers (VLUs) are a common type of complex wound that have a negative impact on people's lives and incur high costs for health services and society. It has been suggested that prolonged high levels of protease activity in the later stages of the healing of chronic wounds may be associated with delayed healing. Protease modulating treatments have been developed which seek to modulate protease activity and thereby promote healing in chronic wounds.

OBJECTIVES

To determine whether protease activity is an independent prognostic factor for the healing of venous leg ulcers.

SEARCH METHODS

In February 2018, we searched the following databases: Cochrane Central Register of Controlled Trials (CENTRAL), Ovid MEDLINE, Ovid Embase and CINAHL.

SELECTION CRITERIA

We included prospective and retrospective longitudinal studies with any follow-up period that recruited people with VLUs and investigated whether protease activity in wound fluid was associated with future healing of VLUs. We included randomised controlled trials (RCTs) analysed as cohort studies, provided interventions were taken into account in the analysis, and case-control studies if there were no available cohort studies. We also included prediction model studies provided they reported separately associations of individual prognostic factors (protease activity) with healing. Studies of any type of protease or combination of proteases were eligible, including proteases from bacteria, and the prognostic factor could be examined as a continuous or categorical variable; any cut-off point was permitted. The primary outcomes were time to healing (survival analysis) and the proportion of people with ulcers completely healed; the secondary outcome was change in ulcer size/rate of wound closure. We extracted unadjusted (simple) and adjusted (multivariable) associations between the prognostic factor and healing.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for inclusion at each stage, and undertook data extraction, assessment of risk of bias and GRADE assessment. We collected association statistics where available. No study reported adjusted analyses: instead we collected unadjusted results or calculated association measures from raw data. We calculated risk ratios when both outcome and prognostic factor were dichotomous variables. When the prognostic factor was reported as continuous data and healing outcomes were dichotomous, we either performed regression analysis or analysed the impact of healing on protease levels, analysing as the standardised mean difference. When both prognostic factor and outcome were continuous data, we reported correlation coefficients or calculated them from individual participant data.We displayed all results on forest plots to give an overall visual representation. We planned to conduct meta-analyses where this was appropriate, otherwise we summarised narratively.

MAIN RESULTS

We included 19 studies comprising 21 cohorts involving 646 participants. Only 11 studies (13 cohorts, 522 participants) had data available for analysis. Of these, five were prospective cohort studies, four were RCTs and two had a type of case-control design. Follow-up time ranged from four to 36 weeks. Studies covered 10 different matrix metalloproteases (MMPs) and two serine proteases (human neutrophil elastase and urokinase-type plasminogen activators). Two studies recorded complete healing as an outcome; other studies recorded partial healing measures. There was clinical and methodological heterogeneity across studies; for example, in the definition of healing, the type of protease and its measurement, the distribution of active and bound protease species, the types of treatment and the reporting of results. Therefore, meta-analysis was not performed. No study had conducted multivariable analyses and all included evidence was of very low certainty because of the lack of adjustment for confounders, the high risk of bias for all studies except one, imprecision around the measures of association and inconsistency in the direction of association. Collectively the research indicated complete uncertainty as to the association between protease activity and VLU healing.

AUTHORS' CONCLUSIONS

This review identified very low validity evidence regarding any association between protease activity and VLU healing and there is complete uncertainty regarding the relationship. The review offers information for both future research and systematic review methodology.

Protease-modulating matrix treatments for healing venous leg ulcers

BACKGROUND

Venous leg ulcers (VLUs) are open skin wounds on the lower leg that occur because of poor blood flow in the veins of the leg; leg ulcers can last from weeks to years, and are both painful and costly. Prevalence in the UK is about 2.9 cases per 10,000 people. First-line treatment for VLUs is compression therapy, but around 60% of people have unhealed ulcers after 12 weeks' treatment and about 40% after 24 weeks; therefore, there is scope for further improvement. Limited evidence suggests non-healing leg ulcers may have persisting elevated levels of proteases, which is thought to deter the later stages of healing; thus, timely protease-modulating matrix (PMM) treatments may improve healing by physically removing proteases from the wound fluid.

OBJECTIVES

To determine the effects of protease-modulating matrix (PMM) treatments on the healing of venous leg ulcers, in people managed in any care setting.

SEARCH METHODS

In September 2016 we searched: the Cochrane Wounds Specialised Register; CENTRAL; Ovid MEDLINE; Ovid MEDLINE (In-Process & Other Non-Indexed Citations); Ovid Embase and EBSCO CINAHL Plus. We also searched clinical trials registries for ongoing and unpublished studies, and scanned reference lists of relevant included studies as well as reviews, meta-analyses and health technology reports to identify additional studies. There were no restrictions with respect to language, date of publication or study setting.

SELECTION CRITERIA

We searched for published or unpublished randomised controlled trials (RCTs) that evaluated PMM treatments for VLUs. We defined PMM treatments as those with a purposeful intent of reducing proteases. Wound healing was the primary endpoint.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed study selection, risk of bias assessment and data extraction.

MAIN RESULTS

We included 12 studies (784 participants) in this review; sample sizes ranged from 10 to 187 participants (median 56.5). One study had three arms that were all relevant to this review and all the other studies had two arms. One study was a within-participant comparison. All studies were industry funded. Two studies provided unpublished data for healing.Nine of the included studies compared PMM treatments with other treatments and reported results for the primary outcomes. All treatments were dressings. All studies also gave the participants compression bandaging. Seven of these studies were in participants described as having 'non-responsive' or 'hard-to-heal' ulcers. Results, reported at short, medium and long durations and as time-to-event data, are summarised for the comparison of any dressing regimen incorporating PMM versus any other dressing regimen. The majority of the evidence was of low or very low certainty, and was mainly downgraded for risk of bias and imprecision.It is uncertain whether PMM dressing regimens heal VLUs quicker than non-PMM dressing regimens (low-certainty evidence from 1 trial with 100 participants) (HR 1.21, 95% CI 0.74 to 1.97).In the short term (four to eight weeks) it is unclear whether there is a difference between PMM dressing regimens and non-PMM dressing regimens in the probability of healing (very low-certainty evidence, 2 trials involving 207 participants).In the medium term (12 weeks), it is unclear whether PMM dressing regimens increase the probability of healing compared with non-PMM dressing regimens (low-certainty evidence from 4 trials with 192 participants) (RR 1.28, 95% CI 0.95 to 1.71). Over the longer term (6 months), it is also unclear whether there is a difference between PMM dressing regimens and non-PMM dressing regimens in the probability of healing (low certainty evidence, 1 trial, 100 participants) (RR 1.06, 95% CI 0.80 to 1.41).It is uncertain whether there is a difference in adverse events between PMM dressing regimens and non-PMM dressing regimens (low-certainty evidence from 5 trials, 363 participants) (RR 1.03, 95% CI 0.75 to 1.42). It is also unclear whether resource use is lower for PMM dressing regimens (low-certainty evidence, 1 trial involving 73 participants), or whether mean total costs in a German healthcare setting are different (low-certainty evidence, 1 trial in 187 participants). One cost-effectiveness analysis was not included because effectiveness was not based on complete healing.

AUTHORS' CONCLUSIONS

The evidence is generally of low certainty, particularly because of risk of bias and imprecision of effects. Within these limitations, we are unclear whether PMM dressing regimens influence venous ulcer healing relative to dressing regimens without PMM activity. It is also unclear whether there is a difference in rates of adverse events between PMM and non-PMM treatments. It is uncertain whether either resource use (products and staff time) or total costs associated with PMM dressing regimens are different from those for non-PMM dressing regimens. More research is needed to clarify the impact of PMM treatments on venous ulcer healing.

A 'test and treat' strategy for elevated wound protease activity for healing in venous leg ulcers

BACKGROUND

Venous leg ulcers are a common and recurring type of complex wound. They can be painful, malodorous, prone to infection and slow to heal. Standard treatment includes compression therapy and a dressing. The use of protease-modulating treatments for venous leg ulcers is increasing. These treatments are based on some evidence that a proportion of slow to heal ulcers have elevated protease activity in the wound. Point-of-care tests which aim to detect elevated protease activity are now available. A 'test and treat' strategy involves testing for elevated proteases and then using protease-modulating treatments in ulcers which show elevated protease levels.

OBJECTIVES

To determine the effects on venous leg ulcer healing of a 'test and treat' strategy involving detection of high levels of wound protease activity and treatment with protease-modulating therapies, compared with alternative treatment strategies such as using the same treatment for all participants or using a different method of treatment selection.

SEARCH METHODS

We searched the following electronic databases to identify reports of relevant randomised clinical trials: The Cochrane Wounds Group Specialised Register (January 2016), the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library) Issue 12, 2015); Ovid MEDLINE (1946 to January 2016); Ovid MEDLINE (In-Process & Other Non-Indexed Citations January 2016); Ovid EMBASE (1974 to January 2016); EBSCO CINAHL (1937 to January 2016). We also searched three clinical trials registers, reference lists and the websites of regulatory agencies. There were no restrictions with respect to language, date of publication or study setting.

SELECTION CRITERIA

Published or unpublished RCTs which assessed a test and treat strategy for elevated protease activity in venous leg ulcers in adults compared with an alternative treatment strategy. The test and treat strategy needed to be the only systematic difference between the groups.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed study selection; we planned that two authors would also assess risk of bias and extract data.

MAIN RESULTS

We did not identify any studies which met the inclusion criteria for this review. We identified one ongoing study; it was unclear whether this would be eligible for inclusion.

AUTHORS' CONCLUSIONS

Currently there is no randomised evidence on the impact of a test and treat policy for protease levels on outcomes in people with venous leg ulcers.