CLABSI Definition, Epidemiology, and Surveillance: What Clinicians Need to Know

Complete overview of CLABSI definition (NHSN criteria), epidemiology (incidence, mortality, cost), CLABSI vs CRBSI distinction, NHSN surveillance methodology, SIR benchmarking, and how CLABSI rates are calculated.

guide•Feb 2026•CLABSI Prevention

CLABSI Definition, Epidemiology, and Surveillance: What Clinicians Need to Know

Central line-associated bloodstream infection (CLABSI) is one of the most serious, costly, and largely preventable hospital-acquired infections. Despite decades of evidence-based prevention efforts, approximately 30,000–41,000 CLABSIs occur annually in US acute care hospitals, each carrying a 12–25% attributable mortality and $46,000–$68,000 in excess hospital costs.

Understanding how CLABSI is defined, measured, and reported is essential for every clinician involved in central venous access — from understanding the “why” behind prevention bundles to interpreting quality data at the unit level.

Parent guide: CLABSI Prevention: Complete Clinical Reference

CLABSI vs. CRBSI: A Critical Distinction

These two terms describe related but distinct concepts and are frequently confused.

CRBSI is a clinical and microbiologic diagnosis used in research and for patient management decisions. CRBSI requires rigorous diagnostic criteria that include:

  • Quantitative blood cultures showing ≥15 CFU from catheter tip (semiquantitative culture)
  • Or differential time-to-positivity: blood cultures from catheter becoming positive ≥2 hours before peripheral cultures drawn simultaneously
  • Or quantitative blood culture: catheter blood culture yield ≥3:1 ratio compared to peripheral culture

CRBSI is used in clinical trials and epidemiologic research because it establishes a definitive causal link between the catheter and the bacteremia.

CLABSI (Central Line-Associated Bloodstream Infection)

CLABSI is a surveillance definition used by NHSN (National Healthcare Safety Network) and CMS for public reporting, quality benchmarking, and payment adjustment. CLABSI uses broader, more operationally accessible criteria:

A CLABSI event is defined as:

  1. A laboratory-confirmed bloodstream infection (LCBI) — positive blood culture with an organism not consistent with a contaminant
  2. AND a central line was in place for >2 calendar days at the time of the BSI event (or was removed the day before)
  3. AND the BSI is not secondary to an infection at another recognized site

Key difference from CRBSI: CLABSI does not require proof that the catheter caused the bacteremia — only that a central line was present. This means:

  • CLABSI is easier to measure at scale (no specialized diagnostics required)
  • CLABSI overestimates true catheter causation (some “CLABSIs” would have occurred without the central line)
  • CLABSI rates are appropriate for population-level surveillance and quality benchmarking, not individual patient diagnosis

NHSN CLABSI Surveillance Criteria

Central Line Definition (NHSN)

Per NHSN 2024 Patient Safety Component Manual: A central line is an intravascular catheter that terminates at or close to the heart or in one of the great vessels (SVC, IVC, pulmonary artery, or cardiac chamber). The device must be used for infusion, withdrawal of blood, or hemodynamic monitoring.

Devices that are central lines for NHSN purposes:

  • PICC lines
  • Non-tunneled CVCs (IJ, subclavian, femoral)
  • Tunneled CVCs (Hickman, Broviac)
  • Implanted ports
  • Hemodialysis catheters (tunneled and non-tunneled)
  • Umbilical venous catheters (UVC) and umbilical arterial catheters (UAC)

Devices that are NOT central lines for NHSN purposes:

  • Peripheral IV catheters (PIV)
  • Midline catheters (tip in axillary/subclavian vein — not a central vein)
  • Intraosseous access devices

LCBI Criteria (Bloodstream Infection Component)

NHSN defines three LCBI criteria:

LCBI Criterion 1: Patient has a recognized pathogen cultured from ≥1 blood culture, AND the pathogen is not related to an infection at another site.

LCBI Criterion 2: Patient has ≥1 symptom (fever, chills, hypotension) AND ≥2 positive blood cultures with a common skin commensal (e.g., coagulase-negative staph), AND cultures drawn on ≥2 separate occasions.

LCBI Criterion 3: (For patients ≤1 year of age): Similar criteria with age-specific symptom definitions.

CLABSI Rate Calculation

The Standard Formula

CLABSI Rate = (Number of CLABSI events / Number of central line-days) × 1,000

This produces a rate expressed as events per 1,000 central line-days — the standard unit for CLABSI reporting.

Central line-days: Each day that any patient in the unit has a central line in place counts as one central line-day. A patient with a PICC for 10 days contributes 10 central line-days.

Example: ICU with 500 central line-days and 2 CLABSI events: CLABSI rate = (2 / 500) × 1,000 = 4.0 per 1,000 central line-days

Standardized Infection Ratio (SIR)

The SIR adjusts a facility’s CLABSI rate for case mix and patient risk, enabling fair comparison across institutions of different types and sizes.

SIR = Observed CLABSI events / Predicted CLABSI events

Predicted events are calculated by NHSN using baseline data from a national reference period, adjusted for unit type (medical ICU, surgical ICU, medical ward, etc.).

Interpretation:

  • SIR = 1.0: Observed CLABSIs equal to expected
  • SIR < 1.0: Fewer CLABSIs than expected (better than predicted performance)
  • SIR > 1.0: More CLABSIs than expected (worse than predicted performance)
  • SIR = 0: Zero CLABSIs observed (aspirational target)

CLABSI Epidemiology

Incidence

  • US acute care hospitals: Approximately 30,000–41,000 CLABSIs annually (HAI Progress Report 2022, CDC)
  • ICU rates: 0.6–1.4 per 1,000 central line-days (2022 NHSN data, major ICU types)
  • Non-ICU inpatient rates: 0.3–0.8 per 1,000 central line-days
  • NICU rates: 0.5–1.9 per 1,000 central line-days (varies by birth weight category)

US CLABSI rates have declined approximately 50–70% from 2001 to 2020, attributed primarily to widespread adoption of evidence-based insertion and maintenance bundles. However, progress has stalled in recent years, and rates in some unit types have been rising post-COVID-19.

Mortality

  • Attributable mortality: 12–25% (varies by pathogen and patient population)
  • 30-day all-cause mortality in CLABSI events: 20–35% in ICU populations
  • Pathogens with highest mortality: Candida spp. (mortality 30–50%); Staphylococcus aureus (mortality 20–30%); gram-negative rods (mortality 15–25%)

Cost

  • Excess cost per CLABSI event: $46,000–$68,000 (various published estimates; 2020 dollars)
  • Additional hospital days: 7–21 excess days attributable to CLABSI
  • CMS non-payment: CLABSI is a CMS non-reimbursable hospital-acquired condition — hospitals absorb the full cost
  • HACRP penalty: CMS reduces Medicare payments by up to 1% for hospitals in the worst-performing quartile on HAI measures including CLABSI SIR

Common Pathogens

Per NHSN data:

  1. Coagulase-negative staphylococci (CoNS) — most common overall, particularly in NICU
  2. Staphylococcus aureus (including MRSA)
  3. Enterococcus spp.
  4. Gram-negative organisms (Klebsiella, E. coli, Pseudomonas)
  5. Candida spp. (particularly in TPN patients, immunocompromised hosts)

Pathogenesis: How Does CLABSI Happen?

Three primary routes of catheter infection:

1. Extraluminal contamination (most common for short-term catheters): Skin organisms at the insertion site migrate along the external catheter surface into the bloodstream. Insertion site asepsis (CHG antisepsis), maximal sterile barrier, and CHG dressings address this pathway.

2. Intraluminal contamination (most common for long-dwell catheters): Hub and connector contamination introduces organisms into the catheter lumen during access events. Scrub-the-hub, needleless connector changes, and ANTT address this pathway.

3. Hematogenous seeding (less common): Bacteremia from a distant site seeds the catheter surface. Prevention of other infections reduces this risk.

Biofilm: Once organisms establish on the catheter surface, they form a biofilm that protects them from antibiotics and host immune defenses. This is why antibiotic therapy alone rarely eradicates CLABSI — catheter removal is usually required.

Why Zero Is Achievable

Several landmark programs have demonstrated that CLABSI can be eliminated:

  • Keystone ICU project (Pronovost et al., 2006, NEJM): 103 Michigan ICUs reduced median CLABSI rate from 2.7 to 0 per 1,000 catheter-days
  • On the CUSP: Stop BSI: Replicated Michigan results nationally across >1,000 hospital units
  • IHI Zero CLABSI program: Evidence-based implementation framework translated bundle science into program design

The implication: most CLABSIs are preventable. The persistence of CLABSI events reflects implementation failures, not limits of clinical science.

Related guides:

Related policies:

References

  1. Pronovost P, et al. (2006). An intervention to decrease CLABSI in the ICU. N Engl J Med, 355(26):2725–2732.
  2. O’Grady NP, et al. (2011). CDC Guidelines for Prevention of Intravascular Catheter-Related Infections. MMWR, 60(RR-1).
  3. CDC NHSN. (2024). Patient Safety Component Manual. Retrieved from cdc.gov/nhsn.
  4. Mermel LA, et al. (2009). Clinical practice guidelines for the diagnosis and management of intravascular catheter-related infection. Clin Infect Dis, 49(1):1–45.
  5. Scott RD. (2009). The direct medical costs of healthcare-associated infections in US hospitals. CDC.