Post on 04-Jan-2016
transcript
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)
Epidemiology and Clinical Medicine
Relationship between
Studies/Assessments
Prevention
Evaluation
Planning
Diagnosis
Treatment
Cure
Care
Examples of Epidemiological Studies
• Link between smoking and lung cancer
Doll & Hill, 1964
Examples of Epidemiological StudiesWater 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
StudyPopulation/
Sample
Exposure to a study factor
Outcome
Unexposed
Exposed
Target Population
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
• Additional morbidity• Prolonged hospitalization• Long-term physical,
developmental and neurological sequelae
• Increased cost of hospitalization• Death
Consequences of Nosocomial Infections
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 nosocomial infections
• Outbreak investigation• Develop written policies
for isolation of patients• Develop written policies
to reduce risk from patient care practices
• Cooperation with occupational health
• Education of hospital staff on infection control
• Ongoing review of all aseptic, isolation and sanitation techniques
• Eliminate wasteful or unnecessary practices
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
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
To cause disease, a pathogenic organism must:
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 PrecautionsApply to ALL patients
• Transmission-based PrecautionsUsed 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, non-intact 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
• 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)
PPE Gown and gloves
Don upon entry to room Remove and discard before leaving the roomPerform hand hygiene after removal
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. Urinary tract infections (UTI)
2. Surgical wound infections (SWI)
3. Lower respiratory infections (LRI)
4. Blood stream infections (BSI)
EPIDEMIOLOGICAL INTERACTIONIntrinsic 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
Event
Action
Data
Information
Health care system
Surveillance centre
Reporting
Feedback, recommendations
An
alysis, in
terpretation
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 patientsICN reviews ICN visits wards