Population Health Flashcards
Main reason for increased life expectancy in Canadians
Decreased infant mortality rate
Lead time bias
Overestimate the survival time from dx b/c screening at occult stage of dz vs dx at later stage
Length time bias
Overestimate the survival time due to screening at one point including more stable cases than aggressive cases, who may have shorter survival times
Screening test must have high sensitivity or specificity?
High sensitivity
Incidence
# new cases in a time interval / persons at risk in time interval Measures rate of new infections
Prevalence
# existing cases at a point in time / persons at risk at that time Measures frequency of disease at a point in time
Top 5 causes of mortality in women in Canada
Cancer Heart disease Stroke Chronic lower respiratory dz Accidents
Top 5 causes of mortality in men in Canda
Cancer Heart disease Accidents Chronic lower respiratory dz Stroke
Specific test
Use to rule IN a hypothesis
Very few false positives
Sensitive test
Use to rule OUT a hypothesis
Very few false negatives
Likelihood Ratio definition
Likelihood that a given test result would be expected in a pt with disease compared with likelihood that same result would be expected in pt without disease
Likelihood ratio + equaiton
Sensitivity / (1- specificity) = (TP / (TP + FN)) / (FP/(TN+FP)
How much the probability of a disease increases if the test is positive
Likelihood ratio - equation
(1-sensitivity)/specificity = (FN/(TP+FN)) / (TN/(TN+FP))
How much the probability of disease decreases if the test is negative
Positive predictive value
Proportion of ppl with +ve test who have the disease
PPV = TP / (TP + FP)
Negative predictive value
Proportion of ppl with -ve test who don’t have the disease
NPV = TN / (TN + FN)
Sensitivity
Proportion of ppl with disease who have a +ve test
Specificity
Proportion of ppl without disease who have a -ve test
Sensitivity/specificity are characteristics of the test or prevalence of the disease?
Test
Likelihood ratio depends on the test or prevalence of the disease?
Test
PPV and NPV depend on the test or prevalence of the disease?
Prevalence
Pretest probability
Probability particular pt has given disease before test/assessment results are known
Posttest probability
Revision of probability of dz after pt has been interviewed/examined/tested
Odds Ratio eq
(A/C) / (B/D)
Ratio of the odds in favour of disease among the exposed to odds in favour of no disease among the exposed
Relative risk
(A/(A+B) / (C/ C+D)
Ratio of risk of a disease among exposed to risk among unexposed
Attributable risk
Rate of health outcome in exposed individuals that can be attributed to exposure
PICO
Population
Intervention
Comparison Group or Control Group
Outcome that you are trying to prevent or achieve
P-value
Denotes the probability that the error of declaring an observed difference to be real rather than by chance
P<0.05
Power
Probabilty of a true positive result
95% confidence interval means
If this test were repeated 100 times, 95 times the result would fall within the interval
Level 1 evidence
Based on RCTs big enough to have low risk of incorporating FP or FN results
Level II evidence
Based on RCTs too small to provide level I evidence
Level III evidence
Based on non-randomized, controlled or cohort studies
Level IV evidence
Based on opinion of respected authorities or expert committees
Level V evidence
Opinions of individuals who have written/reviewed the guidelines based on experience/knowledge
Common diseases spread by contact
Impetigo
Chicken pox
Warts
Common diseases spread by airborne
TB
Common diseases spread by droplet
Influenza
Mumps
Pneumonia
10 step approach to control an outbreak
- Identify the team (local public health units)
- Establish existence of an outbreak
- Verify dx (obain medical records)
- Define a case (Person, place, time)
- Find cases systemically and create a line listing
- Perform descriptive epidemiology and develop hypotheses
- Evaluate hypotheses and conduct additional studies as needed (case-control or cohort studies)
- Implement control measures (can occur at any stage in outbreak)
- Communicate findings
- Continue surveillance
Risk assessment for environmental exposures
HIRA
Hazard Identification
Risk characterization
Exposure Assessment
Contaminants in water
E. coli Salmonella Pseudomonas Shigella Giadia (protozoa) Cryptosporidium (protozoa)
Contaminants in soil
Tetanus
Pseudomonas
Common reportable diseases
AIDS Botulism Campylobacter enteritits Chancroid Chickenpox CHlamydia Cholera CDiff Creutzfelt-Jakob Crypospoidiosis, cyclosporiasis Diphtheria Encephalitis (even if viral) Food poisoning all causes Gastroenteritis institutional Gonorrhea H. influenza b invasive Ebola Hepatitis Legionellosis Listeriosis Lym disease malaria Measles Meningitis Meningococcal Mumps Pertussis Pneumococcal invasive Polio Rabies Rubella Salmonellosis SARS Shigellosis Smallpox Strep invasive Syphilis Tetanus TB Typhoid West nile, yellow fever
