Researchers have found that inconsistent methods for calculating surgical site infections (SSIs) of some procedures are contributing to underestimates of their SSI rates.

The research was published in Infection Control & Hospital Epidemiology and performed by members of the Duke infection Control Outreach Network (DICON). They conducted a retrospective analysis of SSI surveillance data from 11 DICON hospitals over a three-year period (January 2015 through December 2017). The analysis looked at SSI rates of laminectomies and rectal procedures using two different denominators: the current National Health Safety Network (NHSN) definition or only when the laminectomy or rectal procedure was the primary procedure.

Researchers hypothesized that since laminectomies and rectal procedures are commonly performed with "higher-ranking" procedures (fusion procedures and colon procedures, respectively), SSI rates would greatly differ when calculated using the different denominators. More specifically, "… SSIs occurring after combined laminectomy and fusion procedures would be counted as spinal fusion SSIs (but not laminectomy SSIs) and SSIs occurring after combined colon and rectal procedures would be counted as colon surgery SSIs (but not rectal surgery SSIs)," they wrote.

Their hypothesis was correct: The analysis showed significant underestimates of SSI rates for laminectomies and rectal procedures. The researchers wrote, "This analysis showed that the current NHSN method of calculating SSI rates underestimates the SSI rate of procedures, such as laminectomies and rectal surgeries, which are commonly performed alongside higher-ranking procedures."

Dr. Jessica Seidelman, who led the team of researchers, told Infectious Disease News, "If we want to have clinicians and hospitals make informed decisions for their patients, then we need to ensure that the data they use to make those decisions are accurate."

NHSN recently announced it is considering a requirement for hospitals to report ICD-10 or CPT codes when they report SSI denominators. The researchers wrote, "Requiring ICD-10 or CPT codes when reporting SSI data may pave the way for NHSN to further risk-adjust SSI rates based on specific procedure(s) performed. We recommend that the NHSN consider revising their current method for counting SSI denominators by including only primary surgical procedures in denominators when calculating SSI rates and standardized infection ratios."