Epi Flashcards
epidemiology is?
studies:
- distribution
- determinants (risk factors)
Distribution of dz
- frequencies of dz occurrences- in relation to SIZE of pop!
- patterns of dz occurrences- person, place, time-> Descriptive epidemiology!!
Descriptive epidemiology
-person, place, time
Passive surveillance systems
-public health system passively waits for reports to come in
Active surveillance systems
-public health officials go into communities to search for new dz/condition cases
Syndromic Surveillance system
-looks for signs/sx’s of pts related to the dz
Epidemic
-occurrence of dz in excess of normal!!
Outbreak
- epidemic limited to a LOCALIZED inc in occurrence of dz
- also called cluster
Endemic
-CONSTANT presence of dz in a given area that is in excess of normal levels in other areas
Emergency of International Concern
-epidemic that alerts the world to the need for high vigilance
Pandemic
Pandemic
-an epidemic spread world-wide
analytic epidemiology
-why/how
Proportions vs ratios
- proportions- division of 2 related numbers
- ratios- division of 2 unrelated numbers
Incidence vs prevelance
- incidence- NEW occurrences
- prevalence- old and new cases
- point prevalence- at a given point in time
- period prevalence- over a given period of time
Calculate incidence
= # of new cases of illness / # of ppl at risk of illness
those not at risk- already have it or are immune
Calculate prevelance
= total # of cases of illness / # of ppl in population
Exposure and Disease (table)
- probability of an outcome in Exposed
- probability of outcome in non-exposed
Absolute Risk Reduction (ARR)
(absolute = subtract)
-risk difference b/w groups!!!
Relative Risk Reduction (RRR)
= ARR / Runexposed
Number Needed to Treat (NNT)
(# of pts needed to be treated to receive the stated benefit/harm)
=1 / ARR (in decimal format)
-ex- 1 / 0.038 = 27 patients (always round up!)
Risk Ratio
ratio of the risks from 2 diff groups
= Risk of outcome (in exposed) / Risk of outcome (in non-exposed)
Review of Ratios
- ratio > 1.0- MORE likely to occur in numerator group
- ratio < 1.0- LESS likely to occur in numerator group
Interpreting ratios
RR (risk), OR (odds), HR (hazard)
- > 1.0- if RR = 1.53, then comparator group is at 53% INC risk
- > 2.0- if RR = 6.18, then comparator group is at 6.18X GREATER odds
- <1.0- if HR = 0.73, then comparator group has a 27% DECREASED probability
