Active daily surveillance of central-line days (CLDs) in the assessment of rates of central-line–associated bloodstream infections (CLABSIs) is time-consuming and burdensome for healthcare workers. Sampling of denominator data is a method that could reduce the time necessary to conduct active surveillance.

To evaluate the accuracy of various sampling strategies in the estimation of CLABSI rates in adult and pediatric units in Greece.

Daily denominator data were collected across Greece for 6 consecutive months in 33 units: 11 adult units, 4 pediatric intensive care units (PICUs), 12 neonatal intensive care units (NICUs), and 6 pediatric oncology units. Overall, 32 samples were evaluated using the following strategies: (1) 1 fixed day per week, (2) 2 fixed days per week, and (3) 1 fixed week per month. The CLDs for each month were estimated as follows: (number of sample CLDs/number of sampled days) × 30. The estimated CLDs were used to calculate CLABSI rates. The accuracy of the estimated CLABSI rates was assessed by calculating the percentage error (PE): [(observed CLABSI rates − estimated CLABSI rates)/observed CLABSI rates].

Compared to other strategies, sampling over 2 fixed days per week provided the most accurate estimates of CLABSI rates for all types of units. Percentage of estimated CLABSI rates with PE ≤±5% using the strategy of 2 fixed days per week ranged between 74.6% and 88.7% in NICUs. This range was 79.4%–94.1% in pediatric onology units, 62.5%–91.7% in PICUs, and 80.3%–92.4% in adult units. Further evaluation with intraclass correlation coefficients and Bland-Altman plots indicated that the estimated CLABSI rates were reliable.

Sampling over 2 fixed days per week provides a valid alternative to daily collection of CLABSI denominator data. Adoption of such a monitoring method could be an important step toward better and less burdensome infection control and prevention.