**3.2 Sample character**

### **3.2.1 Tissue swabs**

In a report on hip and knee patients organisms cultured from swabs of sinus tracts showed no concordance with the culture results from specimens obtained intra-operatively (Sadiq et al., 2005). There are limited data which suggest that the results of superficial swabs show a reasonable correlation with culture yield from intra-operative tissue biopsy material (Cune et al., 2009). However, other studies have rated results from swab material as both insensitive and unspecific (Font-Vizcarra et al., 2010; Levine & Evans, 2001). Swabs cannot absorb nearly as much material as can be harvested from tissue biopsies or joint fluid, which alone would account for inferior sensitivity. Furthermore, as most etiologic agents of arthroplasty infections belong to the normal skin flora, it is hardly possible to discern between infectious strains and contaminants using swab material. In summary, tissue swabs cannot be recommended to assess prosthetic infections reliably.
