Past Projects

HAI NHSN Denominator Simplification Project

The purpose of the EIP HAI NHSN Denominator Simplification Project is to help inform future NHSN changes that reduce the burden of data collection while maintaining accuracy.

Specifically, this project will:

  • Evaluate the use of a simplified, time–saving method to accurately estimate central line days for use in calculating CLABSI rates

Data for this project are being gathered from more than 100 hospital units across the country.


The Centers for Disease Control and Prevention (CDC) conducts surveillance for healthcare-associated infections (HAIs) through the National Healthcare Safety Network (NHSN). More than 9,000 healthcare facilities now participate in NHSN, and data submitted are now being used for public reporting of HAI rates, inter-facility comparisons, and federal pay-for-reporting and -performance programs. The collection of HAI data to ensure compliance with reporting requirements places substantial burden on infection preventionists in healthcare facilities, and CDC is committed to exploring ways to streamline and simplify NHSN HAI surveillance.

Surveillance Objectives

To evaluate the use of a simplified, less resource intense method to collect denominator data for central line associated bloodstream infection (CLABSI) surveillance in NHSN. Building upon prior efforts [1,2], the purpose of the project goal is to evaluate the use of sampling denominator data one day each week to obtain an estimate of central line days compared to the traditional method of doing daily counts of patients with central lines in each unit engaged in CLABSI surveillance. The results will help to determine how current NHSN denominator data collection practices can be simplified and maintain accuracy.


Participants: Inpatient units (Intensive Care, Wards and Step down) of acute healthcare facilities performing NHSN CLABSI surveillance within one of the 10 EIP states were invited to participate in the project.

This project is being conducted in two separate phases. Phase 1 is a retrospective evaluation CLABSI denominator data logs obtained from hospitals performing NHSN CLABSI surveillance. Each participating inpatient unit submitted at least 6 and up to 12 consecutive months of their existing CLABSI denominator data logs showing daily counts of patient days and central line days. Phase 2 is a prospective evaluation of denominator data collected using sampling methods.

Related Publications
  • Annual Reports and Findings
    • A total of 119 inpatient locations in 63 healthcare facilities participated in phase 1 and submitted CLABSI denominator logs. Data analysis and manuscript preparation is underway.
    • An abstract of data from ICUs that participated in Phase 1 was presented at the SHEA 2011 Annual Scientific Meeting: Evaluation of sampling denominator data to estimate central line days: Validation of methods to reduce data collection burden of the National Healthcare Safety Network icon
    • Phase 2 – data collection on more than 100 inpatient locations is currently underway.
  • Previous publications on the use of sampling to estimate central line days
    • Klevens et al. ICHE 2006;27:338-42.
    • Shelly et al: ICHE 2011;32:727-30.