1 Questions What do you think of when you hear the word surveillance What do you suppose is the definition of surveillance when applied to infection prevention and control Learning Objectives ID: 739808
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Slide1
Introduction to Surveillance
1Slide2
Questions
What do you think of when you hear the word “surveillance”?
What do you suppose is the definition of surveillance when applied to infection prevention and control? Slide3
Learning Objectives
Define surveillance and its role in an infection prevention and control program
Describe types of surveillance and advantages and disadvantages of various surveillance strategies
Give examples of basic measures of disease frequency and describe applicationsSlide4
Public Health Surveillance Definition
The ongoing, systematic collection, analysis, and interpretation of health-related data essential to the planning, implementation, and evaluation of public health practice, closely integrated with the timely dissemination of these data to those responsible for prevention and control Slide5
Surveillance in the Healthcare Setting
Surveillance of healthcare—acquired infections (HAI) is the foundation for organizing, implementing, and maintaining an effective infection prevention and control (IPC) program in the health care facility
“If you don’t measure it, you cannot improve it”
~ Lord KelvinSlide6
Considerations for Surveillance
Frequency
Severity
Cost
Preventability
CommunicabilitySlide7
Methodologic
Issues
Goals
Causal pathway
Information needs
Data sources, methods
Case definition
Evaluation: Balance of attributes
Interpretation of dataSlide8
Interpretation of Data
Issues to Consider
Source of data
Reliability of diagnosis
Potential biases in detection/diagnosis
Definition of a case
Completeness of data
Reporting bias
Consistency in data collection
Completeness
ContextSlide9
Surveillance in the Healthcare Setting:
Objectives
Establish endemic or baseline rate of infections
Compare HAI rates within/between health care facilities
Engage clinical team to adopt best practices
Introduce evidence-based and cost-effective interventions to reduce HAI
Identify and control outbreaks
Evaluate success of the ICP interventions
Identify priority areas to allocate resources
Ultimate aim is to reduce HAISlide10
Components of a Strong
Surveillance Program
Systematic
Ongoing
Data Collection
Analysis
Interpretation
Dissemination
ActionSlide11
Surveillance in the Healthcare Setting
Data must be
Collected
Validated
Analyzed
Interpreted
Disseminated in a timely manner
Collecting and recording data is useless if no further action is taken
Surveillance is synonymous with the premise of “information for action”Slide12
Surveillance in the Healthcare Setting:
Methods
When applicable, data set should include:
Information on the infected patient or resident
Information on medical treatment or procedures at the time of infection
Any underlying medical risk factors of the patient
Information on both numerator and denominator data should be collected for the calculation of rates of infectionSlide13
Surveillance in the Healthcare Setting:
Methods
Flexible to address challenges
T
echnological changes within the health care facility
Short lengths of stay
Healthcare worker shortage and turnover
Increased frequency of invasive procedures or devices
Post-discharge surveillance, as appropriateSlide14
Characteristics of a Strong
Surveillance Program
Targets
Infection prevention
Performance improvement
Patient safety
Public health activities
Engages in mandatory and public reportingSlide15
Characteristics of a Strong
Surveillance Program
Able to identify risk factors for infection
Adverse events
Outbreaks
Emerging infectious diseases
Antibiotic-resistant organisms
Bioterrorist events
Implements control or risk-reduction measures
Monitors the effectiveness of interventionSlide16
Various Methods of Surveillance Used in Infection Control
Methods
Source of Data
Comments
Continuing surveillance of all patients (Prospective, active surveillance)
Medical,
nursing, laboratory records
Time-consuming
and not cost-effective. Infection rates are low in some specialties.
Ward liaison
Twice-weekly visits to wards
Discuss
all patients with staff and review records
Less comprehensive
than continuing surveillance, with similar disadvantages.
Laboratory-based
Laboratory records
only
Depends on samples taken and information on request
form.
Laboratory-based
ward surveillance/selected continuing surveillance
Reporting
of laboratory records and outbreaks by ward staff and continuing surveillance in special units or infections
Early detection of outbreaks and incidence in studies in selected areas of infection.
Adapted from:
Glenister
HM, Taylor LJ, Bartlett CLR,
et al.
An evaluation of surveillance methods for detecting infections in hospital inpatients.
Journal of Hospital Infection
1993; 23:229-42.Slide17
Various Methods of Surveillance Used in Infection Control
17
Strategy
Pros
Cons
Incidence
Provides
data on infections due to all organisms, on all infection sites, and on all units
Identifies clusters
Establishes baseline
infection rates
Allows outbreaks to be recognized early
Identifies risk factors
Expensive and labor intensive
Large amounts
of data collected with little time for a analysis
No defined prevention objectives
Difficult to develop interventions
Not all infections are preventable
Prevalence
Inexpensive
Efficient
use of time; can be done periodically
Over-/underestimates
infection rates; does not capture data on relevant differences
Limited value in small facilitiesSlide18
Various Methods of Surveillance Used in Infection Control
Strategy
Pros
Cons
Site-specific
Flexible and can be combined with other strategies
Identifies
risk factors
No defined prevention strategies or objectives
Denominator
may be inadequate
Unit specific
Focuses on patients at greater
risk
Simplified and reduces personnel
May miss clusters
Denominator
may be inadequate
Objective or priority-based
Can be adaptable to facilities with special populations or resources
Focuses
on specific issues at the facility
Identifies risk factors
Baseline infection rates are not available
May
miss clusters or outbreaks
Adapted from: Perl TM,
Chaiwarith
R. Surveillance: An overview.
Practical Healthcare Epidemiology,
3
rd
Ed., pp. 111-142, Chicago, IL: University of Chicago Press, 2010. Slide19
Types of Surveillance: Outcome Surveillance
Objective: COUNT number of HAIInforms the magnitude of the problem
Disadvantages:
No information on what factors contribute to the problem
No internationally agreed definitions on surveillance
Most commonly used: CDC/NHSN (USA) and ECDC (Europe)
Assumes availability of good diagnostic laboratory support
19Slide20
Types of Surveillance: Process Surveillance
Objective: MONITOR adherence to evidence-based or best practicesEssential to prioritize which processes/steps to monitor
Disadvantages:
Reliability of data
Good compliance does not equate with effectiveness
20Slide21
Example of Outcome vs. Process Surveillance
21
OUTCOME SURVEILLANCE
Counting number of CR-BSIs
PROCESS SURVEILLANCE
Monitoring compliance with CVC care bundle elements
Adapted from
Damani
, N. Manual of Infection Prevention and Control, Third Edition.
New
York: Oxford University Press, 2012.Slide22
Recommended Minimum Elements in a Data Set for Surveillance
Patient /resident informationName or unique identifier, DOB, sex, MRN, ward or unit in facility, name of consultant, date of admission, onset date, date of discharge or death, site of infection/colonization, organism isolated with antibiotic sensitivities
Medical treatment/procedures
At time of infection
Underlying medical risk factors, clinical outcome, assessment of whether the incident was preventable
22Slide23
Linelist: Example
23Slide24
Considerations
All types of surveillance are expensive and time-consumingEssential that definitions and objectives of surveillance must be agreed with the clinical team
Identify resources
Personnel involved in surveillance must be trained
24Slide25
Summary
Assess population and identify those at greatest risk for outcome or process of interestSelect outcome or process for surveillance
Examples of outcomes: HIA, infection or colonization with a specific organism, sharps injuries
Examples of processes: Central line insertion practices, influenza vaccination rates, personnel compliance with protocols
Determine observation period
25Slide26
Summary (continued)
Choose surveillance methodologyMonitor for outcome or process using standardized definitions for all data
collected
Collect appropriate denominator data, if rates are to be calculated
Analyze data
Report in a timely manner
26Slide27
References
Damani
, N. Manual of Infection Prevention and Control, Third Edition. New York: Oxford University Press, 2012.
DHHS/CDC . Outline for Healthcare-Associated Infections Surveillance, 2006.
Tokars
JI, Richards C, Andrus M,
et al.
The Changing Face of Surveillance for Health Care—Associated Infections.
Clinical Infectious Diseases
2004; 39: 1347-52.
Horan TC, Andrus M,
Dudeck
MA. CDC/NHSN surveillance definition of health care—associated infection and criteria for specific types of infection in the acute care setting.
American Journal of Infection Control
2008; 36:309-32.
Haley RW, Culver DH, White JW,
et al.
The efficacy of infection surveillance and control programs in preventing nosocomial infection in US hospitals. (SENIC study).
American Journal of Epidemiology
1985; 121(2):182-205.
Lee TB, Montgomery OG, Marx J,
et al.
Recommended practices for surveillance: Association for Professionals in Infection Control and Epidemiology (APIC), Inc.
American Journal of Infection Control
2007; 35(7):427-40.
HICPAC guidance on public reporting of healthcare-associated infections: Recommendations of the Health care Infection Control Practices Advisory Committee.
Infection Control Hospital Epidemiology
2005; 26(6):580-7.Slide28
“Good surveillance does not necessarily
ensure the making of right decisions,
but it reduces the chances of wrong
ones.”
-Alex Langmuir, NEJM 1963: 268:182-191Slide29
MEASURES OF DISEASE FREQUENCYSlide30
“One’s knowledge of science begins when he can measure what he is speaking about and express it in numbers”
Lord Kelvin 1824-1907 Slide31
Measures in General
Count
Ratio
Proportions
RateSlide32
EPIDEMIOLOGIC MEASURES
Measures of frequency
Incidence
Prevalence
Interrelationship between incidence and prevalence
Slide33
COUNT
Simple measure of quantity
Example
: The number of catheter-related bloodstream infections (CR-BSIs) in Facility X in 2012.Slide34
RATIO
An expression of the relationship between a numerator and a denominator where the two are
separate and distinct
quantities.
Example
:
Injurious falls
occur
in twice as many women aged 65-69
years as in men
of the same
age group.
R
atio
of women to men is 2/1 or 2:1Slide35
PROPORTION
A type of ratio in which the numerator is
included in the denominator.Slide36
EXAMPLE OF PROPORTION
650 HIV+ patients were seen at Facility X.
130 of these patients had
Pneumocystis
carinii
pneumonia (PCP).
Proportion of HIV+ patients seen at Facility X with PCP is 130/650.
130/650 *100 = 20% Slide37
RATE
An expression of the frequency with which an event occurs in a defined population.
A measure of time is an intrinsic part of
the denominator.Slide38
EXAMPLE OF RATE
435/1,000 elderly individuals residing in assisted living facilities had colds
in January
.
(The 435 elderly residents with colds are part of the 1,000 residents in assisted living facilities.) Slide39
TYPES OF RATES
Morbidity rates measure the frequency of
illness within a specific population.
Incidence
Prevalence
Attack rate
Mortality rates measure the frequency of
death within a specific population.
Crude death rate
Cause-specific death rate
Case-fatality rateSlide40
MEASURES OF DISEASE FREQUENCY
Measures that characterize the occurrence of disease, disability or death in populations.
Incidence
PrevalenceSlide41
Measures of Disease Frequency
Incidence
(I):
Measures
new
c
ases of a disease or health event that develop over a period of time.
Prevalence
(P):
Measures
existing
cases of a disease at a particular point in time or over a period of time.Slide42
INCIDENCE
The number of new cases of disease
that occur in a specified period of time.
There are two kinds of incidence measures:
Cumulative incidence (CI)
Incidence density (ID) or incidence rate (IR)Slide43
CUMULATIVE INCIDENCE
The proportion of unaffected individuals who contract disease during a specified time.
CI =
# of new cases in a given time
Total population at risk
(Estimate of individual risk)Slide44
Problems with using CI
To accurately calculate CI we need to follow the
entire population
for the
specified
time interval.
This is rarely possible for two main reasons
People move in and out
People may die from diseases other than disease of interestSlide45
INCIDENCE RATE
The instantaneous potential for change in disease status per unit of time.
IR =
# new case in a given time
Total person-time of observation
Ranges from 0 to
Slide46
What denominator data to collect?
For device-associated HAI incidence rates:
Daily total number of patients AND
Total number of ventilator-days, central line-days, and urinary catheter-days in patient care area(s) under surveillance
Sum daily counts at the end of the surveillance period for use as denominators
Denominator data may be collected by someone other than the ICP as long as that person is trainedSlide47
INCIDENCE RATE EXAMPLE
Three people out of ten persons observed develop disease during a 30-day period of follow-up.
The cumulative rate =
3 cases
in 30 days
10 people
or 1 per 100 per day
(3/10 = 0.3 * 100 = 30/30 days = 1 = incidence for one day per 100 people)Slide48
ATTACK RATE
Another type of incidence rateExpressed as cases per 100 population (or a percentage)
Used to describe the new and recurrent cases of disease that have been observed in a particular group during a limited time period in special circumstances, such as during an outbreak
Attack rate:
Number of new and recurrent cases in a specified time period
Population at risk for same time period
48
X 100Slide49
Prevalence
Measures existing cases of a health condition
Two types of Prevalence
Point prevalence
Period prevalenceSlide50
Point Prevalence
Point Prevalence = C / N
Where C = Number of observed cases at time t
And N = Population size at time t
Point prevalence measures the frequency of disease at a given point in time.Slide51
Point Prevalence
Example
Suppose there are 150 individuals in a population and, on a certain day, 15 are ill with the flu. What is the estimated prevalence for this population
?
P = 15/150 = 10%Slide52
Period Prevalence
Period Prevalence = [C + I] / N
C
= the
number
of prevalent cases at the beginning of the time period.
I = the
number of
incident cases that develop during the period.
N = size of the population for this same time period.Slide53
Example
What is the prevalence of disease X on January 1, 1992
?
Point Prevalence = C/N = 0/10 = 0%Slide54
Example
What is the period prevalence of disease X
between 1990 and 1995?
Period Prevalence = [0 + 5] / 12 = 42%Slide55
Prevalence
Useful for:
Assessing the health status of a population.
Planning health services.
Not Useful for:
Identifying risk factorsSlide56
Another Example
Suppose we followed a population of 150 persons for one year, and 25 had a disease of interest at the start of follow-up and another 15 new cases developed during the year.
What is the
point prevalence
at the start of the period?
What is the
period prevalence
for the year?
What is the
point prevalence
at the end of period?
What is the
cumulative incidence
for the one year period?Slide57
Another Example
Suppose we followed a population of 150 persons for one year, and 25 had a disease of interest at the start of follow-up and another 15 new cases developed during the year.
What is the
point prevalence
at the start of the period?
25/150 = 0.17 = 17%
What is the
period prevalence
for the year?
(25 + 15) / 150 = 0.27 or 27%
What is the
point prevalence
at the end of period?
Not known
What is the
cumulative incidence
for the one year period?
15/125 = 0.12 = 12%Slide58
FACTORS THAT INCREASE PREVALENCE
Cases move into population
Healthy people leave population
Longer living with disease
Longer duration of disease
Increased number of susceptible/at-risk individualsSlide59
FACTORS THAT DECREASE PREVALENCE
Cases move out of population
Healthy people move into population
People being cured
Shorter duration of disease
Decreased number of susceptible/at-risk individualsSlide60
INTERRELATIONSHIP BETWEEN INCIDENCE AND PREVALENCE
Prevalence depends on both incidence and disease duration.
If the incidence is low but the disease duration is
long, the proportion of the population with
the disease at a particular time is high
compared to the incidence.Slide61
EXAMPLE OF INTERRELATIONSHIP
In the beginning of the AIDS epidemic, the incidence rate of AIDS increased quickly. However, the disease duration was short because everyone died in a few years. Therefore, the prevalence was low.
Incidence and
duration =
prevalenceSlide62
EXAMPLE OF INTERRELATIONSHIP
Today, the incidence rate is not increasing as quickly but the duration of survival is considerably longer. Therefore, the prevalence is now much higher.
Incidence and
duration =
prevalenceSlide63
PREVALENCE AND INCIDENCE
When the disease is stable:
Prevalence = Incidence * Disease DurationSlide64
Incidence vs.
Prevalence
Incidence
(I):
Measures
new
cases of a disease that develop over a period of time.
Prevalence
(P):
Measures
existing
cases of a disease at a particular point in time or over a period of time.Slide65
Prevalence vs. Incidence
Prevalence can be viewed as describing a pool of disease in a population.
Incidence describes the input flow of new cases into the pool.
Fatality and recovery reflects the output flow from the pool.Slide66
Summary
Risk
(cumulative incidence) is the probability that an event will occur within a given time-interval
Rate
(incidence rate) is a measure of how rapidly the events occur in a population
In contrast to measures of
incidence
(
risk and rate),
prevalence
deals with existing (as opposed to newly occurring) health-related statesSlide67
Linelist: Example
67