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Understanding Surveillance
Data and NHSN Basics
Module 2
Joan N. Hebden MS, RN, CIC
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Learning Objectives
• State three differences between clinical and surveillance definitions of infection
• Explain the data on the device-associated NHSN output table
• Define the value of presenting both device-associated infection rates and device utilization ratios when providing feedback to bedside providers
• Define the value of calculating both incidence and prevalence rates for trending multi-drug resistant organisms
• Define the importance of an epidemic curve during an outbreak investigation
• Understand how to use the NHSN analytic tools for identifying events and the significance of differences in data
Current State of HAI Surveillance
Courtesy of Daniel Pollock, MD: NHSN -Changing Purposes March 12, 2014
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Competency in Infection Prevention
IPC Domain: Novice IP
• Epidemiology and
Surveillance
– Conducts surveillance:
standardized , basic case finding
methods and application of HAI
definitions
– Is learning to use NHSN
– Performs manual chart review,
data abstraction and data
collection
Defining HAI Surveillance
• SHEA Consensus Panel on essential activities of IPC
programs in hospitals -1998)
– HAI surveillance most important data management activity
– Surveillance process to include: standardized definitions of
numerators and denominators, identification and description of data
sources and data collection personnel and selection of appropriate
methods of measurement (Category I recommendation)
– Additional Category I recommendation emphasized the need for
appropriate data analysis to monitor and improve HAI outcomes
Scheckler WE, Brimhall D, Buck AS, et al. Requirements for infrastructure and essential activities of infection
control and epidemiology in hospitals: a consensus panel report. Am J Infect Control 26(1):47-60
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Source: Stone, P.W., Dick A., Pogorzelska, M., Horan, T.C., Furuya, E.Y., Larson, E. Staffing and Structure of Infection Prevention and Control Programs. American Journal of Infection Control, Volume 37, Issue 5, June 2009, Pages 351-357. Note: Data total does not equal 100 due to rounding.
Data-Related
Activities
How IPs Spend Their Time
Prevention
Activities
44.5
15
12.9
13
8.86.1
Collecting, Analyzing & Interpreting Data on the Occurrence of Infections
Policy Development & Meetings
Daily Isolation Issues
Teaching Infection Prevention & Control Policies and Procedures
Other (e.g., Product Evaluation, Employee Health & Emergency Preparedness)
Activities Related to Outbreaks
Understanding Surveillance Data
Surveillance Definitions
• Identify trends within a
population for the purpose
of prevention and research
• Comply to limited, pre-
determined data components
• Objective: clinical judgment
introduces potential bias
Clinical Diagnoses
• Identify disease in, and
treatment needs for,
individual patients
• All diagnostic information is
used for decision making
• Subjective: clinical
judgment is valued
Adapted from Bridson, KA NHSN Patient Safety Component Manual
2014
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• Essential elements of surveillance• Assess the patient population and identify those at greatest risk
for the outcome and process measures of interest: outcome =
HAI; process = practices aimed at HAI prevention
• Select the outcome and process measures
• Determine the surveillance time period
• Choose the surveillance methodology
• Monitor the selected measure using standardized definitions
• Collect denominator data for rate calculation
• Analyze the data
• Report the data in a timely manner
HAI Surveillance Overview
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• Surveillance methodology
• CDC recommends active, prospective, targeted
surveillance that yields risk-adjusted incidence rates
• ACTIVE: trained personnel (IP) vigorously look for HAIs
using a variety of data sources
• PROSPECTIVE: during the patients’ hospitalization and for
SSIs post-discharge for the defined surveillance period
• TARGETED: surveillance objectives defined with focus on
specific events, organisms, procedures
• RISK-ADJUSTED: variations in the distribution of major
risk factors associated with the occurrence of an event are
controlled – allows for inter-and intra-hospital comparisons
HAI Surveillance Overview
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• INCIDENCE: count only new events during the defined time
period; PREVALENCE: count all events -new and previously
existing
• Numerator data collection
� What to collect
�Demographic: name, gender, admit date, medical record
number, medicare beneficiary number: REGISTRATION
(ADT)
� Infection data: onset date, site of infection, location of HAI
onset
�Risk factors: devices, procedures, comorbidities e.g. diabetes,
obesity
�Laboratory and microbiology data
�Radiology
HAI Surveillance Overview
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� How to collect
�Screen ADT data for high-risk patient admissions and
patients admitted with infection – recent discharge?
�Reviews lab and microbiology data – positive cultures,
unusual organisms e.g Legionella pneumophila
�Ward rounds
�Reviews disparate data of patients suspected to have an HAI
– physician and nursing notes, radiology, surgery reports, lab
• Denominator data collection
• Device days
• Patient admissions/days
• Surgical procedures
HAI Surveillance Overview
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� Complete
� Accurate
� Timely
High Quality Surveillance Data
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High Quality Surveillance Data
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HAI Type Step 1 Step 2
CLABSIReview every positive blood
cultureReview for presence of central line
SSIIdentify and review all post-
op patients and
readmissions (30d or 90d)
• Review readmission reports; ICD-9 DC
coding
• Review reoperation reports
CAUTIReview every positive urine
cultureReview for presence of a urinary catheter
LabID
Review all final test results
for specific events e.g
MRSA bloods, C. diff toxin
assays
• If positive in ED, review for admission
to inpatient unit on same day
• Review length of time between positives
on the same patient
Review of a minimum clinical dataset for all patients up to the
point where the HAI is ruled out
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CDC/NHSN Surveillance Definitions
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http://www.cdc.gov/nhsn/PDFs/pscManual/17pscNosInfDef_current.pdf
Device-Associated (DA) Infection Rates
• Calculated as an incidence density rate (IDR)
• To calculate the IDR, you need:
– Numerator: # of new cases for a time period
– Denominator: person-time during the same period
– A multiplier for interpretation
• NHSN DA rates:
– Central Line-Associated BSI
– Catheter-associated UTI
– Ventilator-associated pneumonia
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Calculating a DA rate for CAUTI
• What measure of person-time is used in the
calculation of CAUTI rates in NHSN?
1. Patient days
2. Patient admissions
3. Catheter insertions
4. Catheter days
Calculating a DA rate for CAUTI
• ANSWER: 4. Catheter days
• Calculation is based on person-time for those at
risk of infection for that HAI type
• Example:
# of CAUTIs in the MICU for a specific month x 1000
# of catheter days for that same month
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Interpreting DA Rates
• How would you
interpret the MICU’s
CAUTI rate of 1.827?
1. 1.8 per 1000 catheter
days
2. 1.8%
3. 1.8 per 1000 pt. days
4. 1.8 times higher than
the national
Interpreting DA Rates
• How would you
interpret the MICU’s
CAUTI rate of 1.827?
1. 1.8 per 1000 catheter
days
2. 1.8%
3. 1.8 per 1000 pt. days
4. 1.8 times higher than
the national
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Interpreting DA Rates: The p-value
Determining with 95% probability that your outcome did
not occur by chance: p = <0.05; very small probability that
it occurred by chance – 5%
Interpreting DA Rates: The p-value
The p-value is included in the DA rates output in NHSN:
What is compared? Your facility’s location DA rate to the
pooled mean for the same location
Is the CAUTI rate for the MICU significantly different
from the NHSN pooled mean based on the p-value?
1. Yes
2. No
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Interpreting DA Rates: The p-value
Is the CAUTI rate for the MICU significantly different
from the NHSN pooled mean based on the p-value?
1. Yes
2. No The p-value is > 0.05
How well are we doing?
• External Benchmarking
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NHSN Data Summary
• Aggregated report of HAI surveillance data
• Purposes:– Allow for trend recognition
– Provide risk-adjusted metrics for inter-facility comparisons and local QI
– Assist facilities in developing surveillance and analysis methods that permit timely recognition of patient safety issues and prompt intervention
NHSN Data Summary: Pooled Mean
(265/78,825) x 1000 = 3.4
Pooled mean is not an “average” –
weighted mean that pools the data within
the strata
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Interpreting DA Rates: Percentiles
• Percentile provides a value at which a percentage of the
distribution falls at or below; the NHSN output data table includes
the exact percentile of where your rate falls on the published
Distribution
• The 25th percentile, 25% of the facilities had lower rates and 75%
had higher rates
Interpreting DA Rates: Percentiles
• Why use percentiles?
– Provide the full range of rates in the location type
– “Where do we fall in that range?”
– Assists with establishing an external benchmark
other than the NHSN pooled mean
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NHSN Source of Aggregate Data Used for Comparisons
( pooled means/percentiles)
Use of DU Ratios
• Device Utilization (DU)
Ratios
• A measure of the use
of invasive devices
which constitutes an
extrinsic risk factor for
HAI
• May serve as a
marker of severity of
illness of the patient
population
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DU Ratios
0.32 = 32% of the patient-days were also central-line days
29% of the reporting MICUs had a DU at or lower than the MICU’s DU ratio
Turning Data into Knowledge!
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0
2
4
6
8
10
12
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CCU MICU CSICU SICU NCICU PICU NICU NTCC MTCC T6CC
Above NHSN Target �At NHSN Target �Less than NHSN Target �
NHSN pooled mean comparison
Above NHSN Target �At NHSN Target �Less than NHSN Target �
NHSN pooled mean comparison
Rate
per
1,0
00 C
L D
ays
ICU Location
ICU Central Line-Associated BSI Rates -
By Quarter
Quarterly Data – 3 Quarters of 2009
Horizontal Bar = NHSN Target by ICU
Type
0
0
Surveillance for MDROs
• Rationale:
– Detect newly emerging antimicrobial resistance
patterns
– Identify vulnerable patient populations
– Assess the need for and effectiveness of interventions
• Why?
– Increasing incidence
– Severity of infections
– Changing in reporting requirements
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Surveillance for MDROs
• Estimating infection burden:
– Overall burden of MDROs in the facility
– Incidence of HA-MDRO bacteremia; + BC are easy to track, highly likely to represent infection; shown to decrease in response to interventions
– Specific organism device- or procedure-associated incidence e.g CRE infections among catheterized patients, MRSA sternal wound infections in CABG pts.
Cohen et al. SHEA/HICPAC Position Paper. Recommendations for MDRO Metrics
Oct. 2008; 29(10).
Surveillance for MDROs
• Estimating exposure burden
– “colonization pressure” – the amount of exposure of
patients to MDRO colonized or infected pts. who
could potentially transmit the organism to them
– Overall prevalence of MDRO clinical cultures: newly
identified and historical
– MDRO prevalence based on clinical cultures alone
underestimates the full reservoir; if facility is
performing active surveillance screening, should be
included
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Surveillance for MDROs
– The proportion of persons in a population with a particular disease at a:
• specific point in time (point prevalence)
• Over a specified time period (period prevalence)
– Point prevalence surveys assist with identification
of areas with high endemicity where enhanced
surveillance may be useful
– Admission prevalence: the magnitude of MDRO
importation into the facility
An Outbreak of A. baumannii
• Clonal outbreak of MDR-AB in a SICU; no environmental source identified
• Baseline mean attack rate 3/100 pts./month; from Feb 1-Mar 22, attack rate rose to 16/100 pts/month ( 18 infections): dropped to 4/100 pts./month after educational intervention
• Case-control study ( 36 non-infected): only independent risk factor was the prevalence of pts. with MDR-AB infections
• “Colonization pressure” increased the likelihood of cross -transmission
D’Agata EMC, et al. ICHE 2000; 21:588-
91
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Assessment of the Prevalence of MDR-AB in Maryland
• Purpose: to assess the state-wide prevalence of MDR-AB
among mechanically-ventilated patients
• Define the burden of MDR-AB in both acute-care and LTAC
patients
• 2-week period prevalence
• The high prevalence of AB and the molecular findings with
evidence of a highly endemic process and patient-to-patient
transmission defined a need to increase interventions aimed at
reducing AB acquisition and spread
Thom KA, et. al. ICHE September 2012; 33(9)
Assessment of the Prevalence of MDR-AB in Maryland
Is there a statistically significant difference in the proportion of
acute vs. LTC facilities with A. baumannii?
1. Yes
2. No
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Assessment of the Prevalence of MDR-AB in Maryland
Is there a statistically significant difference in the
proportion of acute vs. LTC facilities with A. baumannii?
1. Yes. P-value is <0.05
2. No
NHSN Surveillance and
Analysis Tools
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Ventilator-Associated Event (VAE) Surveillance Tool
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• http://www.cdc.gov/nhsn/labid-
calculator/index.html#
MDRO & CDI LabID Event Calculator
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MDRO & CDI LabID Event Calculator
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NHSN Statistics Calculator
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NHSN Statistics Calculator – Compare
Two Proportions
• Publicly reported HAI surveillance data should be defined by standardized case-finding and consistently applied objective criteria
• Statistical data provided through NHSN output tables and the published data summary allows for benchmarking of rates which are risk-adjusted and can be used for inter-facility comparisons
• Incidence rates are valuable for estimating infection burden
• Prevalence rates are valuable for evaluating MDRO exposure burden and for assessment of targeted interventions
• An epidemic curve is an essential tool for detecting and tracking infection occurrences which exceed endemic levels
Summary
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