Surveillance Quality in Reporting Nosocomial Bloodstream Infection Rates—Reply

In Reply: Drs Cohen and Benenson highlight challenges in assessing central line–associated BSI rates, particularly with respect to denominator measurement. Central line–associated BSI rates are calculated with a denominator of central-line days, which provides important risk adjustment among hospitals that differ in patient severity of illness.¹ The denominator reflects “at-risk” days, and theoretically patients with infected central lines should be removed from the denominator.² However, many patients have more than 1 central line, and these patients remain eligible for additional central line–associated BSIs beyond the first event. Since enumerating central-line days is already labor intensive at most hospitals and the days are often aggregated to the unit level, it is unlikely that achieving a marginally more accurate denominator would meaningfully impact central line–associated BSI rates. For example, since on average less than 1% of central-line days incur an infection, the adjustment would be minimal.