**4.1 The value of both pre-operative and intra-operative sampling**

We are convinced that pre-operative identification of the causative agent is a key factor for successful eradication of arthroplasty infections. It enables the design of individualized systemic and localized antibiotic therapy, while intra-operative tissue samples confirm the diagnosis and allow modification of the systemic antibiotic regimen if necessary. The diagnostic workflows we have established to identify hip and knee infections are outlined below.

To minimize the effect of false-negative results, we call for an antibiotic-free interval of 4 weeks before sampling for microbiological diagnosis. At our clinic we withhold perioperative antibiotic prophylaxis until samples have been drawn, and we have not experienced adverse outcomes.
