Harris 1995.

Methods	Nested case‐control design in a cross‐sectional study: wounds divided on clinical criteria into those in granulating/epithelialising and non‐granulating phases Setting: not reported Country: UK Duration of follow‐up: none, case‐control Treatments: not reported
Participants	18 participants with VLUs (area 8.5‐75 cm²; duration, 6 months ‐ 40 years) Mean age: 73 (SD 12) years (calculated from IPD) Sex: not reported Stage of ulcer: not reported Ulcer duration: mean: 14 (SD 13) years (calculated from IPD) Ulcer size at baseline: mean: 31 (SD 18) cm² (calculated from IPD) Wound infection: none (all confirmed as not clinically infected) Number of wounds 18 (presumed) Inclusion criteria: not explicitly stated but VLUs of > 6 months' duration were included Exclusion criteria: not reported
Prognostic factors	MMP (unspecified) (continuous data); collagenases (unspecified); total activity (μg collagen degraded/hour/mg protein in fluid); also reported separately for latent and active. Measurement method was ³H‐labelled type 1 collagen assay: trypsin was added (to cleave latent MMP to active MMP) and the net total activity measured, endogenous inhibitors of collagenase not removed (active collagenase was also measured without trypsin treatment) Time of measurement: baseline Wound fluid sampling method: occlusive dressings (Tegaderm dressing, 4‐6 hours (foam))
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Selection bias	High risk	No details on selection; wounds were classified into healing and non‐healing within a cohort of participants; not matched and longitudinal features not reported.
Attrition bias	Unclear risk	Moderate: 2/12 participants in non‐healing group missing. Unclear if this was important
Prognostic factor measurement	Unclear risk	Moderate: MMP type not specified. 1995 study; unclear if measurement appropriate and insufficient details
Outcome measurement	High risk	Type of case‐control study; healing and non‐healing identified, but not matched at the outset
Adjustment factors	Unclear risk	Moderate: at least half, but not all, key adjustment factors taken into account in design or analysis (ulcers judged not to be "clinically" infected and confirmed in microbiology; infection taken into account in design)
Analysis and reporting	Unclear risk	Moderate: data had to be extracted from graph
Overall risk of bias	High risk