DISEASE DETECTIVES: TERMS YOU NEED TO KNOW

descriptive epi

generate hypothesis. what, when, where, and who (distribution)

analytic epi

test hypothesis. why and how. (determinants)

clinical approach

diagnosis and treatment of individuals, medical care, immunization etc.

public health approach

control & prevent disease in population

descriptive studies

generate hypothesis. examine patterns of occurrence. focus on person, place, and time.

analytic studies

test hypothesis. use comparison groups to identify/quantify association and identify causes

experimental studies

proves causation. studies through trials, introduces variables, and study effects.

randomized control trial

human experiment. distributing treatments to individuals. proves causation.

double-blind

both participants and experimenter blind

gold standard

randomized control trial w/ double blind

triple-blind

patients, administrators of treatment, and experimenter are blind

single-blind

only participants blind

observational studies

study exposure status. observe people without changing anything. work backwards or forwards.

cross-sectional study

survey. snapshot in time/

case-control study

mostly retrospective. compare people with & without disease to find common exposures.

cohort

compare people exposed and unexposed to see if people develop disease.

attrition bias

people who drop out of study differ from those who remain in study

acquiescence bias

respondents tend to agree with the statement when given options like “agree or disagree” or “yes or no”

base rate fallacy/false pos paradox

ignoring base rate (statistics) in favor of distinguishing details. ex. librarians are shy, so steve must be a librarian.

berkson’s paradox

taking control group from a hospital. bc of this, results from study are show negatie association btwn risk factor and disease

ceiling effect

when drug reaches maximum effect, so can not observe effectiveness.

channeling bias

groups decided based on prognosis/severity of illness

courtesy bias

reluctance to give negative feedback to person asking questions

confounding bias

3rd variable distorts other variables associated with outcome

effect modification

independent and dependent variable affected because disease modified for varying levels of 3rd variable

confirmation bias

process, look for, and interpret information based on their beliefs

detection bias

differences between groups in how outcomes are determined. ex. ppl w/ disease are more likely detected due to more intense follow up

berkson’s bias

if controls are hospitalized bc exposure that is related to health outcome under study, then measure of effect may be weakened

confounding bias

related both to independent & dependent, primary exposure of interest is distorted by other 3rd variable associated w/ outcome

responding bias

When respondents have tendency to choose highest/lowest response available

Golem Effect

When lower expectations are placed upon individuals which leads to poorer performance by individuals

healthy participant bias

ppl who report having treatment may have lower frequency of disease as they care more abt their health

hawthorne effect

change in bahavior because they know they are being watched

length time bias

overestimation of survival bc relative excess of cases detected that are slow progressing, fast progressing cases are detected after symps

maternal recall bias

mothers of children w/ birth defects are more likely to remember drugs they took during pregnancy rather than mothers of normal children

non-response bias

low response to survey → underestimate results

Pygmalion/Rosenthal effect

high expectations lead to improved performance

researcher bias

Researcher’s beliefs/expectation influence research design/data collection process

Response/survey bias

# of diff situs where respondents wrong/false answer to self-report questions

Recall bias

differences in way subjects remember or report exposures or outcomes.

reporting bias

systematic difference btween reported & unreported data

self report bias

difference between self reported data and the true data

selection bias

systematic difference in method of choosing study groups; groups of subjects differ in ways other than exposure, mostly w/ volunteers

Simpson’s/amalgamation Paradox/Yule Simpson Effect

trend or result that is present when data is put into groups that reverses/disappears when data is combined

type 1 error (false pos)

rejecting the null hypothesis when its true

type 2 error (false neg)

failure to reject the null hypothesis

Control

public policy to restrict spread of agent to acceptable level before ppl begin to protect against agent. Ex:malaria, diarrhea

Elimination

reduce to 0 incidence, 0 incidence of disease in particular area bc efficient efforts. Continued interven required. Ex measles, polio, neonatal tetanus

Eradication

permanent 0 of worldwide incidence. intervention no longer needed Only small pox

Extinction

Agent no longer exists in nature and lab

Consistency

repeatable in diff populations, in diff study designs & @ diff times

Specificity

specific cause can only cause 1 specific outcome

Analogy/Alternative explanation

consider multi hypo before making conclusions abt if association is causal

Strength of association

relation between risk factor & outcome. Strong association, more likely causal relation. Measures like odds ratio

Temporality

exposure must precede outcome

Dose response/ Biological gradient

more exposure = more disease

Biological plausibility

biological research supports conclusions made

Coherence

exposure is ALWAYS associated w outcome

Experiment

state can be altered, either prevented/accelerated, by appropriate experimental process

Passive surveillance

(provider-initiated)gather diseases reported by healthcare pros, w/o prompting, receive reports

Active surveillance

(health department-initiated)health agencies contact health providers seeking reports

sentinel surveillance

specific area which trends are observed & analyzed, healthcare providers agree to report cases of specific diseases. Data signals trends, monitor burden of disease in community

syndromic surveillance

focuses on symptoms for any abrupt changes that could signify potential outbreak

contact tracing

ind ppl who recently been in contact w/ sick ppl

agent

organisms that cause disease.

reservoir

where agents thrive/reproduce.

portal of exit

where agent leaves reservoir.

mode of transmission

method of transfer by which organism moves from 1 place to another

portal of entry

opening allowing microorganism to enter host

Susceptible host

someone who cannot resist organism invading body, resulting in infection

stage of susceptibility

exposure/enough factors sufficient for disease process to begin in susceptible host

stage of subclinical disease

after disease process triggered, pathological changes occur, disease is asymptomatic(

stage of clinical disease

most diagnoses are made @ early stage, disease is symptomatic.

stage of recovery, disability, death

end of disease process

secular trend

occurrence of disease over prolonged period,usually years

seasonal trend

periodic variation in the occurrence of disease over time

active immunity

long-term; occurs when person is exposed to live pathogen, develops disease, & becomes immune as result of primary immune response.

passive immunity

short-term immunization by injection of antibodies, like gamma globulin, that are not produced by recipient's cells.

herd immunity

protecting whole community from disease by immunizing critical mass of its population

acquired

develops after exposure to particular antigen /after antibodies are transferred from 1 indi to another(used in vaccs)

innate immunity

defense system your’e born w/, protects against all antigens. Ex:mucus traps flu, keeping out of lungs

adaptive immunity

destroy invading pathogens & toxic molecules produced

infectivity

proportion of exposed persons who become infected(ability of infectious agent to cause infection/ability of pathogen to establish infection)

pathogenicity

proportion of infected persons who develop clinical disease(ability to cause disease)vacc Effectiveness(Risk of unvaccinated ppl MINUS risk of vaccinated ppl)OVER risk of unvaccinated ppl/# of ppl infected over population

virulence

proportion of persons w/ clinical disease who become severely ill/die(ability of infectious agent to cause severe disease/ability of pathogen to harm host, can be described using morbidity/mortality)

endemic

disease present in population @ all times. Ex: HIV sub-saharan africa, malaria SA, cholera SE Asia

hypoendemic

Constantly present @ low incidence, small populations; outbreaks where transmission occurs all yr long. Ex:hookworm in US

hyperendemic

All ppl in population are affected, high rate, all age groups affected, ex:dengue fever

holoendemic

Not equally present in all age groups, everyone infected @ some point in time, ex:malaria. high prevalence in children

mesoendemic

disease w/ moderate rate of infection, often used to describe prevalence of malaria in a local area

enzootic

low level of disease constantly in animal population similar to endemic for humans

outbreak

(localized epidemic)uptick in incidence of disease above historical/typical levels for time/place/person

epidemic

 large #s of ppl over wide geographic area affected

mixed epidemic

Outbreak is spread from same source and/or person-person(common source + propagated)

epizootic

outbreak in large animal population similar to epidemic in humans

pandemic

epidemic occurring over very wide area(several countries/ continents)& usually affecting large proportion of population

cluster

aggregation of cases over particular per esp. cancer & birth defects closely grouped in time & space regardless of whether # is more than expected #.(often expected # of cases isn't known)

sporadic

disease that occurs infrequently & irregularly. Ex. tetanus, rabies, plague

idiopathic

disease w/ unknown cause that arises spontaneously