Are the classic signs of infection in concordance with results from percutaneous aspiration to diagnose infection in pressure injuries?

Aim: To explore the concordance between the presence of classic signs of infection and the positive diagnosis identified by the microbiological culture of fluid collected by percutaneous aspiration.

Background: The classic signs of infection are commonly applied in some contexts to confirm infection in pressure injuries, but its accuracy has been questioned in chronic wounds. Little is known about the concordance of this method with others, such as the deep fluid culture from pressure injuries collected by percutaneous aspiration.

Design: Multicentre, cross-sectional observational study.

Methods: Pressure injuries of patients from four health centres were analysed. Three types of data were recorded between February 2011 and March 2012: i) socio-demographic and clinical data, ii) number and type of infection signs and iii) microbiological results of deep fluid culture from injuries. The concordance was calculated with the kappa index to find a possible concordance between both methods.

Results: On 40·2% (n = 47) of injuries, two or more classic signs of infection or purulent exudate as unique sign were present, while the total positive results in the microbiological cultures were 50·4% (n = 59). The disparity of positive results, depending on the location and the stage of the pressure injury and the method applied, suggested a poor concordance between methods. The -0·092 kappa index confirmed the non-concordance of the analysed methods.

Conclusions: The tandem strategy is not useful to indicate an infection in pressure injuries. We advocate exploring other signs of infection and the adoption of other more reliable signs together with the classic signs of infection.