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Protease-modulating matrix

'Unclear’ whether PMM treatments for healing VLU are beneficial

• It is uncertain whether PMM dressing regimens heal VLUs quicker than non-PMM dressing regimens (low-certainty evidence from one trial with 100 participants) (HR 1.21, 95% CI 0.74 to 1.97)
• It is uncertain whether there is a difference in adverse events between PMM dressing regimens and non-PMM dressing regimens (low-certainty evidence from five trials, 363 participants) (RR 1.03, 95% CI 0.75 to 1.42)

A Chochrane review examining evidence on the effects of treatments designed to lower the levels of protease in venous leg ulcers (VLUs) has found that the evidence from clinical trials is ‘unclear’ as to whether there is a benefit of 'protease-modulating matrix' (PMM) dressings on hard-to-heal VLUs, in conjunction with compression treatment, compared with other dressings. Nevertheless, the paper states that there is limited evidence suggesting it is possible therefore, the authors state that if such “PMM dressings can give healing times that are shorter by a few weeks, compared to other dressings or there is a moderate improvement in the probability of medium term healing, this could be important to patients.”

The review, ‘Protease-modulating matrix treatments for healing venous leg ulcers’, published in the ‘Cochrane Database of Systematic Reviews’, sought to examine if treatments that remove protease from wounds could help venous leg ulcers to heal more quickly, and if these treatments were harmful in any way. In 2012, they noted that VLUs cost about £1,700 per year to treat each person with an open venous leg ulcer in the UK. PMM dressings are designed to remove proteases from wound fluid, and this is expected to help the wound heal.

In September 2016, the investigators searched for as many relevant randomised controlled trials that compared PMM treatments with other treatments for venous leg ulcers. They found 12 studies involving a total of 784 people. They identify ten studies that treated all the participants with compression therapy as well as the dressings. Most of the people in the trials had wounds that were not getting better or had been there a long time.

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.

Overall, they report that:

  • It is uncertain whether PMM dressing regimens heal VLUs quicker than non-PMM dressing regimens (low-certainty evidence from one 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, two 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 four trials with 192 participants) (RR 1.28, 95% CI 0.95 to 1.71).
  • Over the longer term (six 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, one 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 five trials, 363 participants) (RR 1.03, 95% CI 0.75 to 1.42).

It was also unclear whether resource use is lower for PMM dressing regimens (low-certainty evidence, one trial involving 73 participants), or whether mean total costs in a German healthcare setting are different (low-certainty evidence, one trial in 187 participants). One cost-effectiveness analysis was not included because effectiveness was not based on complete healing.

“The existing evidence is uncertain and so there is a need for further investigation in a large RCT,” the paper concludes. “Such a trial could usefully compare two different PMM dressings and an advanced dressing: two PMM dressings are proposed because we cannot be sure there is a class effect. We suggest the PMM dressings should be those specifically designed and marketed as protease-modulating (e.g. Promogran and UrgoStart). The population would be people with hard-to-heal VLUs or it might be useful to include both venous and mixed venous-arterial ulcers, as stratified groups. Healing should be investigated as a time-to-event outcome, with regular monitoring times and at least six months' follow-up. It might be useful to additionally monitor protease levels.”

To acccees this paper, please click here