Risk factors for infection in patients with chronic leg ulcers: A survival analysis

Abstract

Aim:This study aimed to validate the relationships between possible predictive factors and clinically diagnosed infection in adult patients with chronic leg ulcers. Methods:This study used a sample of 636 adult participants whose ulcers were diagnosed as either venous, arterial or mixed aetiology leg ulcers and had no clinical signs of infection at recruitment. Data were extracted from recruitment to 12 weeks from six longitudinal prospective studies from 2004 to 2015. Survival analysis was used to investigate mean time-to-infection, including the Kaplan-Meier method and the Cox proportional-hazards regression model. Results:The sample included 74.7% venous, 19.6% mixed and 5.7% arterial leg ulcers. There were 101 (15.9%) participants diagnosed with infection at least once within 12 weeks of follow-up. Mean time-to-infection was 10.89 weeks (95% CI = 10.66-11.12). After adjustment for potential confounders, a Cox proportional hazards regression model found that depression, using walking aids, calf ankle ratio <1.3, wound area ≥10 cm 2 and ulcers with slough tissue at recruitment were significant risk factors for wound infection. Conclusion:This study has validated the predictive ability of factors which have been found in a cross-sectional study to be significantly associated with infection in patients with leg ulcers, including venous leg ulcers, arterial leg ulcers and mixed aetiology leg ulcers. Results showed that patients with chronic leg ulcers, who either presented with depression, used walking aids, had a calf ankle ratio <1.3, a wound area ≥10 cm 2 or an ulcer with slough tissue, had greater likelihood of developing infection compared to those without these factors.

Validation of predictive factors for infection in adults with chronic leg ulcers: A prospective longitudinal study

“…The current study found no associations between other medical conditions and infection, including peripheral vascular disease, diabetes mellitus, rheumatoid arthritis and unhealthy weight, which is similar to those from Bui, Finlayson, et al (). Corticosteroids were reported to increase skin and soft tissue infection (Germano et al, ) and acute wound infection (Finan et al, ).…”

“…The ability to recognise people at risk of developing infection early lies in the understanding of associations between potential risk factors and infection. The current research, a prospective study, confirmed the finding from a previous study relied on a secondary analysis by Bui, Finlayson, et al () that the use of walking aids can be a risk factor for developing infection in patients with CLUs. Walking aids applied to all devices that were used by patients to assist their mobility.…”

“…While there could be a bidirectional relationship between depression and infection as patients with infection had a higher rate of depressive symptoms (Cancienne, Mahon, Dempsey, Miller, & Werner, ), depression has been identified as a risk factor for infection in general skin infections (Andersson et al, ) and in acute wounds (Cancienne et al, ; Olsen et al, ). Depression was significantly associated with infection with the risk of infection increasing five times in those who were diagnosed with depression in a previous study of 561 patients with chronic leg ulcers (Bui, Edwards, et al, ), and patients with CLUs who were also diagnosed with depression were three times more likely to have infection compared to those without depression in another study of 636 patients with chronic leg ulcers (Bui, Finlayson, et al, ). In the current study, we found 15.6% of patients reported being diagnosed with depression.…”

“…There was no significant correlation between these three factors. However, in previous studies, there were six other factors (depression, CPD, CAC <1.3, ulcer with slough tissue, ulcer area ≥10cm 2 and ulcer with heavy exudate level) found to be significantly associated with infected leg ulcers in multivariate tests (Bui, Edwards, et al, ; Bui, Finlayson, et al, ); thus, these factors were also included in a Cox regression model for the current study. However, as all patients with depression or CAC <1.3 in the current study were censored (as they did not have infection within 12 weeks), these variables were excluded from the Cox regression model.…”

“…Although these two studies were limited in design to a secondary data analysis, findings identified several risk factors for infection, which required further investigation (Bui, Edwards, et al, ; Bui, Finlayson, et al, ). These factors included physical and psychological factors (chronic pulmonary disease, depression, diabetes and use of walking aids) and lower‐limb factors (calf–ankle circumference ratio <1.3, ulcer with slough tissue, ulcer with an area ≥10 cm 2 and ulcer with heavy exudate; Bui, Edwards, et al, ; Bui, Finlayson, et al, ). There was a conflict of evidence with regard to wound duration, as it was found to be associated with colonisation of S. aureus (Tosh et al, ); however, three other studies did not confirm this relationship (Bui, Edwards, et al, ; Bui, Finlayson, et al, ; McInnes et al, ).…”