Comparison of two semi-quantitative wound swabbing techniques to establish the clinical efficacy in identifying the causative organism(s) in infected cutaneous wounds

Abstract

All wounds are contaminated with bacteria; the decision to perform a wound swab is based on the presence of clinical signs and symptoms of infection. In acute wounds these include: pain, erythema, localised oedema, heat and purulence. Patients with chronic wounds may display covert signs of infection such as: an increase in serous exudate, delayed healing, friable granulation tissue, pocketing at the wound base and malodour. A wound swab should only be performed when the wound has been clinical diagnosed as infected. The problem that arises for the clinician is which method of collecting the wound swab should be employed.The aim of this research was to compare two semi-quantitative wound-swabbing techniques (Levine versus Z technique) to establish which method was more effective in determining the presence of bacteria in cutaneous wounds. The Levine technique involves rotating the wound swab over a 1 cm[superscript]2 area of the wound with sufficient pressure to express fluid from within the wound tissue. The Z technique involves rotating the swab between the fingers as the swab is manipulated in a 10-point zigzag fashion across the wound without touching the wound edge or peri wound skin. There is a scarcity of evidence in the literature to support the use of one method over the other, hence the need to undertake the study.A prospective randomised study of two paired wound swabbing techniques (Levine versus Z technique) was conducted. Two semiquantitative wound swabs were collected no more than five minutes apart, on each patient. The order of wound swab technique was randomised. All wounds were cleansed with normal saline using an aseptic technique prior to specimen collection. Differences between the detected microbiological bioburden values were analysed with t-test for paired sample.There were 28 males and 22 females. Acute wounds represented 42% (n=21) of the study population and the remaining 58% (n=29) were chronic wounds. Clinical signs of infection were present in 42% of patients with acute wounds. All patients with chronic wounds had one or more overt clinical sign of infection. A statistical difference in the number of organisms was detected between the two swabbing techniques. The Levine method detected more organisms (t = 15.46, p = <0.001), than the Z technique. There was also a statistically significant difference in the number of organisms detected in acute and chronic wounds. In acute wounds the Levine technique detected more organisms (t = 9.55, p = <0.001). In chronic wounds the Levine technique detected more organisms (t = 12.04, p <0.001).The Levine method proved to be more sensitive in detecting organisms present in cutaneous wounds in both acute and chronic wounds. Based on the results of this study, the Levine technique is the recommended method for collecting a wound swab.