Comparison of infection rate using different methods of assessment for surveillance of total hip replacement surgical site infections

BACKGROUND: The surveillance of surgical site infections (SSI) has been undertaken in many centres worldwide to ascertain the extent of the problem and where possible, to improve the incidence rates, thereby decreasing the undesirable outcomes. The study investigates the processes and outcomes of total hip replacement SSI surveillance carried out in Dunedin Public Hospital in 2004. METHODS: Two hundred and six patients were enlisted in the study and 189 primary replacements and 22 revision replacements were carried out. Four methods of diagnosis of SSI were applied: (i) clinician diagnosis; (ii) ASEPSIS score; (iii) presence of pus cells; and (iv) assessment by a clinical microbiologist. Infection rates were calculated according to the risk indexes. RESULTS: The incidence of infections varies considerably among these four methods. The infection rates for risk index 0 were 4.35% (method 1), 2.61% (method 2), 0.87% (methods 3 and 4); and for risk indexes 1 and 2 were 4.17% (method 1), 2.08% (method 2), 1.04% (methods 3 and 4). CONCLUSION: There is a need for accurate infection data so that the appropriate follow-up responses, including infection control measures for total hip replacement SSI can be carried out. The preponderance of elderly patients in the study who are frequently on 'polypharmacy' regimens adds pressure to the need to obtain true infection rates. This is because when antimicrobials are prescribed to them, drug interactions, adverse effects of the antimicrobials and the selective pressure of antimicrobials causing resistances may occur. More resources and a multidisciplinary approach are required for future studies of similar nature.