Validation of Orthopaedic Surgical Site Infection Surveillance in Wales: Preliminary Results from 2 Pilot Sites

Background: Surveillance of surgical site infections (SSI) following elective primary hip and knee arthroplasty procedures has been mandatory in Wales since 2003. CDC definitions of infection, provided in the form of a diagnostic algorithm are used. Surveillance forms are completed at the end of the inpatient stay and at the patients’ 6-8 week follow up visits to fracture clinics. SSI rates resulting from the surveillance have been higher than those reported in the literature and those of partners in the Pan-Celtic collaboration. A validation study was required to assess the robustness of the surveillance system in Wales.  
Objective: To evaluate the accuracy and completeness of reported data and determine if the definitions for SSI are being used correctly.

Methods: A case note review was conducted by members of the Welsh Healthcare Associated Infection Programme (WHAIP) team, Public Health Wales NHS Trust, on all procedures reported with an SSI in 2008 and on a 10% random sample of those without an SSI. The reviewers were blind to the SSI status of the selected procedures to prevent bias when reviewing the notes. SSI status was determined using the algorithm. The SSI surveillance form was completed using the case notes alone and additional comments and observations were recorded on a separate comments form. Questionnaires were scanned using an Optical Mark Reader and original results and reviewer results for the same patients compared by matching on serial number. 
Results: 154 case notes were validated in the 2 pilot sites. There was more than 90% agreement between the original and reviewers responses for 12 out of 20 data items. For the SSI status of the patient at the end of the inpatient stay, overall there was agreement in 94% (144/154) of procedures. However, for the 12 procedures originally reported as inpatient SSIs, only 2 were reported as SSI in the validation (17% agreement). Additionally, for the 16 procedures reported as post-discharge SSIs, only 9 were reported as SSI in the validation (56% agreement) and 2 were identified as possible post discharge infections due to lack of evidence in the case notes to satisfy the SSI criteria. It was noted that patients were often prescribed antibiotics post discharge without any symptoms documented in the notes.

Conclusions: Initial results from the two pilot sites suggest over reporting of SSI in Wales. This highlights a need for further training on the use of the SSI diagnostic algorithm.

The validation will be carried out at all sites carrying out elective orthopaedic surgery in Wales to determine whether conclusions drawn so far are representative. The validation will also expand to incorporate caesarean section SSI surveillance.