Download Methods Epidemiological investigation

Methods of Epidemiological
investigation
Epidemiology is the
scientific process applied
to the control of infections
in the healthcare setting.
Origin of the term ‘epidemiology’
• epi - ‘on, upon, at, by, near, over, on top of,
against, among’
• demos - ‘common people or citizenry’
• ology - ‘the study of’
• epidemiology =‘Study of disease among
the population’
Epidemiology is about
Populations
• Groups of people not individuals
• It answers population questions
– aetiology of disease
– prevention of disease
– Extent/distribution of disease (allocation of
effort & resources in health facilities and
communities)
Relationship between
Epidemiology
and
Clinical Medicine
Studies/Assessments
Diagnosis
Prevention
Treatment
Evaluation
Cure
Planning
Care
Examples of Epidemiological
Studies
• Link between smoking and lung cancer
Doll & Hill, 1964
Examples of Epidemiological Studies
Water
fluoridation:
•Communities
that had low
natural water
fluoride levels
had high levels
of dental caries
•Communities
that had high
natural water
fluoride levels
had low levels
of dental caries
Uses of Epidemiology(Gordis,
2000)
• Identifies aetiology or causes of disease
including the risk factors for the disease.
• Determine the extent of the disease in the
community
• Examines natural history of disease and
prognosis of disease
• Investigates and controls disease outbreaks
Uses of Epidemiology(Gordis,
2000)
• Describes and monitors the population health
and the patterns of disease
• Evaluates new preventive and therapeutic
interventions and modes of health care delivery
• Provides information to inform public policy
decisions
Key components of
epidemiological studies
Target
Population
Study
Population/
Sample
Exposure to a study
factor
Exposed
Outcome
Unexposed
Key components of epidemiological
studies
• Target population is the population a
researcher wants to make
generalizations about
• Study population is the group a
researcher wishes to study (sometimes
the same as the target population)
• Study sample is a group of subjects
chosen for study to represent the study
population
Key components of epidemiological
studies
• Study factor
– is a element that is being investigated to see if it is
a determinant of a particular health problem
– or if it reduces the impact of a particular health
problem.
– Study factors can include
• risk factors for a health problem,
• interventions (therapeutic or
preventative) to ameliorate a health
condition,
• diagnostic tests or techniques and
• environmental exposures.
• Exposure is contact with or possessing a
particular study factor
• Exposed group is a group whose
members have had contact with or
possess a study factor
Key components of epidemiological
studies
• Unexposed group is a group that has
not had contact with a cause of, or
possess a characteristic that is a
determinant of, a particular health
problem.
• Outcome is any or all of the possible
results that may stem from an exposure
or study factor.
• How is Hospital Epidemiology different
from Healthcare Epidemiology?
• Healthcare Epidemiology extends the
practice into the outpatient areas.
History of infection control and
hospital epidemiology in the USA
• Pre 1800: Early efforts at wound prophylaxis
• 1800-1940: Nightingale, Semmelweis, Lister, Pasteur
• 1940-1960: Antibiotic era begins, Staph. aureus nursery
outbreaks, hygiene focus
• 1960-1970’s: Documenting need for infection control
programs, surveillance begins
• 1980’s: focus on patient care practices, intensive care units,
resistant organisms, HIV
• 1990’s: Hospital Epidemiology = Infection control, quality
improvement and economics
• 2000’s: ??Healthcare system epidemiology
modified from McGowan, SHEA/CDC/AHA training course
Why do we need infection
control??
Hospitals and clinics are complex
institutions where patients go to have
their health problems diagnosed and
treated
But, hospitals, clinics, and
medical/surgical interventions
introduce risks that may harm a
patient’s health
Consequences of Nosocomial Infections
• Additional morbidity
• Prolonged hospitalization
• Long-term physical, developmental
and neurological sequelae
• Increased cost of hospitalization
• Death
What is healthcare epidemiology?
The fundamental roles of healthcare
epidemiology are to:
– Identify risks
– Understand risks
– Eliminate or minimize risks
What is the role of
healthcare epidemiology?
Identify risks to patient’s health
• Find nosocomial infections
– surveillance
• Identify and study risk factors for
nosocomial infections
– understand epidemiologic principles and
methods
– understand nosocomial pathogens
– what is it about healthcare institutions that
increases risk?
What is the role of
healthcare epidemiology?
Eliminate or minimize risks to a patient’s
health
• organize care to minimize risk
– eliminate risk factors
– work around risk factors
– develop improved policies and procedures
• educate physicians and nurses regarding
risks
• study risk factors to learn more about
them and how to eliminate them
Responsibilities of the Infection
Control Program
• Surveillance of
• Education of
nosocomial infections
hospital staff on
infection control
• Outbreak investigation
• Develop written policies • Ongoing review of
all aseptic, isolation
for isolation of patients
and sanitation
• Develop written policies
techniques
to reduce risk from
• Eliminate wasteful
patient care practices
or unnecessary
• Cooperation with
practices
occupational health
Areas of interest to a
healthcare epidemiologist
• Surveillance for
nosocomial
infection
• Patterns of
transmission of
nosocomial
infections
• Outbreak
investigation
• Isolation
precautions
• Evaluation of
exposures
• Employee health
• Disinfection and
sterilization
• Hospital
engineering and
environment
– water supply
– air filtration
• Reviewing policies
and procedures for
patient care
Organizing for Infection
Control
• Requires cooperation, understanding and
support of hospital administration and
medical/surgical/nursing leadership
• There is no simple formula:
– Every facility is different
– Every facility’s problems are different
– Every facility’s personnel are different
• The facility must develop its own unique
program
Organizing for Infection
Control
• Main elements
– Establish policies and regulations to reduce risks
• Develop with clinicians (physicians and nurses)
– Develop and maintain a program of continuing
education for hospital personnel
– Use scientific (epidemiologic) methods to study
problems and test hypotheses
Disease Transmission
To cause disease, a pathogenic organism must:
Leave original host
Survive in transit
Be delivered to a susceptible host
Reach a susceptible part of the host
Escape host defenses
Multiply and cause tissue damage
Disease
Routes of Transmission
• Contact: Infections spread by direct or indirect contact
with patients or the patient-care environment (e.g.,
shigellosis, MRSA, C. difficile)
• Droplet: Infections spread by large droplets generated
by coughs, sneezes, etc. (e.g., Neisseria meningitidis,
pertussis, influenza)
• Airborne (droplet nuclei): Infections spread by particles
that remain infectious while suspended in the air (TB,
measles, varicella, variola)
Precautions to Prevent Transmission of
Infectious Agents
• Standard Precautions
Apply to ALL patients
• Transmission-based Precautions
Used in addition to Standard Precautions
• Contact
• Droplet
• Airborne
http://www.cdc.gov/ncidod/dhqp/pdf/guidelines/Isolation2007.pdf
Standard Precautions
• Hand hygiene
• Respiratory hygiene and cough etiquette
• Personal protective equipment (PPE)
Based on risk assessment to avoid contact
with blood, body fluids, excretions,
secretions
• Safe injection practices
• Environmental control
• Patient placement
PPE for Standard Precautions
• Gloves – when touching blood, body fluids,
secretions, excretions, mucous membranes, nonintact skin, contaminated items
• Gowns – during procedures or patient-care activities
when anticipating contact with blood, body fluids,
secretions, excretions
• Mask, eye protection (goggles or face shield) –
during procedures or patient care activities likely to
generate splashes or sprays
Transmission-based
Precautions
Contact Precautions
• Patient placement
– Single room or cohort with patients with same infection
– If neither is possible, ensure patients are separated by at
least 3 ft (1 m)
*Change PPE and perform hand hygiene between
patient contacts regardless of whether one or both are
on contact precautions
Contact Precautions
PPE
Gown and gloves
Don upon entry to room
Remove and discard before leaving
the room
Perform hand hygiene after removal
• Environmental measures/patient care equipment
– Clean patient room daily using a hospital disinfectant, with attention
to frequently touched surfaces (bed rails, bedside tables, lavatory
surfaces, blood pressure cuff, equipment surfaces).
– Use dedicated equipment if possible (e.g., stethoscopes, bp cuffs)
Droplet Precautions
• Patient placement
– Single room or cohort with patients with same infection
– If neither is possible, ensure patients are separated by at least
3 ft (1 meter)
– Surgical mask on patient when outside of patient room
– Negative pressure or airborne isolation rooms not required
PPE
• surgical mask
• Don upon entry into room
• Eye protection (goggles or face
shield) if needed according to
standard precautions
Airborne Isolation
 Airborne infection isolation room (AIIR)*
 Monitored negative air pressure in relation to corridor
 6-12 air exchanges/hour
 Air exhausted outside away from people or recirculated by
HEPA filter
 Surgical mask on patient when not in AIIR (limit movement)
 PPE – filtering facepiece respirator
 For all personnel inside negative pressure room
* Natural ventilation alone or combined with mechanical ventilation may
be a practical alternative in some settings.
http://www.who.int/csr/resources/publications/AI_Inf_Control_Guide_10May2007.pdf
TYPES OF NOSOCOMIAL
INFECTION BY SITE
1.
2.
3.
4.
Urinary tract infections (UTI)
Surgical wound infections (SWI)
Lower respiratory infections (LRI)
Blood stream infections (BSI)
EPIDEMIOLOGICAL INTERACTION
Intrinsic host susceptibility
Age, Poor nutritional status,
Co morbidity, severity of
underlying disease
Agent factors
varieties of organisms
Institutional and human
Reservoirs & their
virulence
Environmental factors
hospital location,
diagn procedures,
immunosuppressive,
chemotherapy, antibiotics,
med & surgical devices,
exposure to infected patients
or health workers,
asymptomatic carriers
MODES OF TRANSMISSION
A) BY CONTACT
1) Direct - between Patients and between
patient care personnel
2) Indirect - contaminated inanimate objects
in environment (Endoscopes etc)
3) Droplet infections by large aerosols
B) THRO COMMON VEHICE like Food, Blood & blood
products, Diagnostic reagents, Medications
C) AIRBORNE e.g. legionellosis, aspergillosis
D) VECTORBORNE – by flies
Why surveillance?
• NCI cause of morbidity and mortality
• One third may be preventable
• Surveillance = key factor
– an infection control measure
– overview of the burden and distribution of NCI
– allocate preventive resources
• Surveillance is cost-efficient!!
The surveillance loop
Health care
system
Surveillance
centre
Reporting
Action
Analysis,
interpretation
Event
Data
Information
Feedback,
recommendations
Objectives
•
•
•
•
•
•
•
•
•
Reducing infection rates
Establishing endemic baseline rates
Identifying outbreaks
Identifying risk factors
Persuading medical personnel
Evaluate control measures
Satisfying regulators
Document quality of care
Compare hospitals’ NCI rates
Who
• All hospitals?
• All departments?
• All specialties?
• Other health institutions?
Surveillance of one or more types
of NCI
Urinary tract infections
Lower respiratory tract infections
Surgical site infections
Bloodstream infections
Conjunctivitis
Others…
Targeted surveillance
• Special patient population
(surgical, medical, paediatric, intensive)
• Diagnostic and therapeutic procedures
(endoscope, haemodialysis, catheterization,
blood transfusion)
• Specific pathogens
(staphylococcus aureus, MRSA,
clostridium difficile, norovirus)
Variables
• Administrative data
– Id, address, dates of admission, discharge..
• Patient related factors:
– Age, sex, severity of underlying disease
• Procedures
– Surgery
– Devices (e.g. catheters)
• Treatment, diagnosis
– Use of antibiotics
When?
• During hospital stay?
– Frequency of data collection
• After discharge?
– When and how?
How?
• Two main surveillance methods
– incidence
– prevalence
• Variations within these methods
Methodological issues
• Definitions NCI
– Cut off 48 or 72 hours?
– Criterias from Centers for Disease Control and
Prevention (hospital)
– McGeer (long-term care facilities)
Risk variables
• Case finding
– Active or passive
– By whom?
– After discharge?
– Prospective or retrospective?
SURVEILLANCE
Important means of monitoring HAI
Early detection of trends outbreaks
1. Laboratory Based
Microbiology Laboratory lists +ve organisms
ICN reviews ‘Alert organisms’ reported
2. Ward Based
Ward staff monitor patients
ICN reviews ICN visits wards