Calculating the cost of SSIs

Based on 8.6 million surgical procedures in the UK per annum,1 an infection rate of 4.2%2 and treatment costs of approximately £2,100 per infection,3 the total cost of surgical site infection in the UK is estimated at £758 million per annum. However, research carried out by the University Hospitals of Leicester suggests that the figures currently cited could be just the tip of the iceberg. Speaking at a symposium on SSIs, Professor Judith Tanner, chair of clinical nursing research, De Montfort University and University Hospitals of Leicester, revealed how a thorough surveillance programme was undertaken in an attempt to calculate the cost of infections at the Trust, with thought provoking results. “Understanding the cost of an individual episode is irrelevant,” she pointed out, “Trusts need to know the frequency of infection at their organisation to begin to make an accurate calculation.” Although some Trusts use the Health Protection Agency (HPA) figures as a basis to extrapolate costs, these are largely based on surveillance that is voluntary, with the exception of orthopaedics (See Table 1). Prof. Tanner warned that although the HPA figures are useful, they are not a true representation of the actual rates of infection: “It is a misconception that infections will present within six days,” she commented. “Infections continue to present at day 30 and day 40, so they are not just happening to inpatients. Another misconception is that patients with infections, which occur once they are discharged into the community, will return to hospital and have their SSI noted. “Many patients have their infection treated by their GP or practice nurse and therefore do not return to the hospital. If you were to base your costs of infection at your Trust on HPA prevalence figures, or those that present during inpatient stay, you will significantly underestimate the total figure,” she warned. At the end of 2007, the tissue viability lead at Leicester raised concerns about the rising spend on VAC dressings for patients who had undergone colorectal surgery. The head of surgery was approached and explained that SSI rates were not being monitored, so it was impossible to assess whether rates had increased or not. As a result, a team was established to conduct rigorous, gold standard surveillance of SSIs.

Surveillance

A surveillance programme was undertaken between January 2008 and May 2008, and was carried out in the areas of colorectal and primary breast surgery. The teams used the HPA and CDC definitions of SSI, while a dedicated surveillance nurse was trained and seconded for five months. The surveillance nurse performed a full 30 day follow up by telephoning patients on day 10, day 20, and day 30, and conducting a questionnaire. If there was a positive response to any of the questions, which indicated an SSI, she visited the patient in their own home to conduct direct observation of the wound. She also assessed a wide range of possible risk factors such as whether the patient smoked, for example. “Of the 105 patients that were included in the surveillance for colorectal surgery, 27% (29/105) had a surgical site infection. This rate of infection does not appear to be an isolated local issue, however – we found a further three studies that used rigorous, gold standard surveillance methods which found similar results. While the HPA’s figures are just 8.3% in this surgical specialty, thorough surveillance programmes suggest that the actual figures are considerably higher,” Prof. Tanner commented. “If we had used the HPA’s data, the estimated costs would have been around three times less than the actual cost incurred by the Trust.”