Identification of High-Risk Lower Extremity Wounds Using Point-of-Care Test for Bacterial Protease Activity; A Single-Centre, Single-Blinded, Prospective Study.

Clinician observation is the mainstay to determine if wound infection is present, and focuses on presence of erythema, purulence, and odour. However, non-visible bacterial protease activity can delay wound healing and lead to complications. In this study, a point-of-care test to detect the presence of bacterial protease activity (BPA, tested with Woundchek Bacterial Status test) was appraised. A total of 130 patients with lower extremity wounds were recruited in vascular and podiatry clinics, and across two time-points 182 BPA tests were conducted subsequent to initial (blinded) clinician's wound appraisal. Clinical opinion ('no infection', 'possible' or 'definite' infection) and BPA result (negative or positive test) had a moderate Kendall's tau-c rank correlation coefficient of 0.32 (P < 0.001). Binary logistic regression analysis and principal component analysis showed that infection determined by clinical opinion was significantly associated with abovementioned clinical signs and a positive BPA test. However, a positive BPA result was also significantly linked with wound severity, such as number of lesions, chronicity and size. Throughout a 12-week follow-up period, median ulcer size was larger for wounds positive for BPA test at baseline (P 0.001) and week-12 (P 0.036; both Mann-Whitney U-test) respectively. As a pilot initiative, clinical staff were allowed to act on the BPA result if they wished; in 11 out of 71 test-positive cases (15%) this happened and antimicrobial dressing was applied instead of planned standard dressing. These results show that protease-releasing bacteria may be active in ulcers that do not (yet) exhibit hallmark signs of infection, and are associated with delayed healing. Targeted point-of-care testing for bacterial protease activity may have the potential to identify and enable pro-active (antimicrobial) management of these high-risk wounds.