Objective: To assess antibiotic use as a complementary neonatal intensive care unit (NICU) infection measure to the central line-associated blood stream infection (CLABSI) rate.

Study Design: Patient days (PDs), line days, antibiotic (AB) use, CLABSI and other proven infections were analyzed in consecutive admissions to two NICUs in the USA over 3 and 6 months, respectively, from 1 Jan 2008 until discharge.  An antibiotic course (AC) consisted of one or more uninterrupted antibiotic days (AD), classified as perinatal or neonatal, if started 3 days or 4 days post birth and as rule-out sepsis or presumed infection (PI) if treated 4 days or 5 days, respectively.  Events were expressed per 1000 PD and aggregated by conventional treatment categories and by clinical perception of infection certainty: possible, presumed or proven.

Results: The cohort included 754 patients, 18,345 PD, 6637 line days, 718 AC and 4553 AD.  Of total antibiotic use, neonatal use constituted 39.2% of ACs, and 29.0% of ADs,  When analysed per 1000 PD, antibiotic use to treat PIs vs CLABSIs, was either 14-fold (CI, 6.6 to 30) higher for ACs (5.40 vs 0.38/1000 PD, P less than 0.0001) or 8.8-fold (CI, 7.1 to 11) higher for ADs (48.3 vs 5.5/1000 PD, P less than 0.0001).

Conclusions: CLABSI rates, present a lower limit of NICU-acquired infections, whereas antibiotic-use measures, about 10-fold higher, may estimate an upper limit of that burden.  Antibiotic-use metrics should be evaluated further for their ability to broaden NICU infection assessment and to guide prevention and antibiotic stewardship efforts.

See also associated editorial, 'Metrics for NICU antibiotic use: which rate is right?', p.511-513.