screening Flashcards
definition:
early detection of
-
-
-
- disease
- precursors of disease (increase the likelihood of developing a particular disease)
- susceptibility to disease (developing a disease but do not show any signs of disease)
what is the goal of early detection
identify the disease early on before symptoms arise
briefly explain early detection according to WHO
the presumptive identification of those who probably have disease from those who do not have by means of rapidly applied test in apparently healthy individuals (screening test)
[screening of large populations to detect and implement measures]
briefly explain the iceberg of disease
it is the relationship between different levels or stages of a disease within a population
visible tip - clinically apparent cases of the disease that have been diagnosed and treated
submerged portion - many undiagnosed, asymptotic or pre-clinical cases that are not yet visible
in conclusion, the no. of undetected cases in the early stages is much larger than the diagnosed cases. submerged portion is important for prevention, early detection and controlling the overall burden of disease.
briefly explain the pyramid of health and disease
top
(1) diseased, diagnosed and controlled
(2) diagnosed, uncontrolled
(3) undiagnosed, misdiagnosed disease
(4) risk factors for disease [increase their susceptibility to developing disease]
(5) free of risk factors
bottom
when is screening test conducted
the start of preclinical phase - biological onset of disease
briefly explain the pre clinical phase
incubation period - communicable period
latency period - noncommunicable period
[incubation period is the time from exposure to symptom onset, while the latency period is the time from exposure to becoming contagious or infectious to others]
define diagnosis
symptoms has not showed yet but is identified in the screening process
true or false:
there is symptoms during preclinical phase
false - no symptoms
true or false:
in screening test, there is no symptoms and it does not have pathological changes
false - have pathological changes
what is the difference between prescriptive screening and proscriptive screening
detection of disease
prescriptive screening - high risk patient
proscriptive screening - entire population
what are the objectives of screening programs
describe natural history of disease of a condition
prevention of contagion and protection of public’s health
detect of disease precursor of disease a guide to medical care of individual (prescriptive screening)
what are the uses of screening
- case detection - popu tht has high cases (men = prostate cancer, women = breast cancer)
- case/ disease control (covid)
- research (vaccination, development of drugs)
- health edu - for awareness
- prescriptive screening - screening to those who are exposed aka high risk (family history of cancer = screening for that type of cancer)
- proscriptive screening - all the ppl in the community for the benefit of other ppl (covid-19, test kits )
- natural history of disease
- public awareness
briefly explain screening process (based on the diagram)
identify the indiv who potentially have a particular disease from an apparently well population
the process:
1. applied to healthy populations (all)
2. -ve test = dont have disease under study at that time
3. +ve test = potentially have disease or risk at developing in the future
4.+ve cases then undergo diagnostic procedureed to confirm presence or absence of disease
5. those confirmed = implement interventions
6. -ve cases = no diseases, intervention not required
positive on test, no disease =
positive on test, disease present =
positive on test, no disease = false positive
positive on test, disease present = true positive
briefly explain diagnostic and screening test
diagnostic - provide yes/no answer about the presence of a disease (gives final confirmation)
screening - identify indiv who may need further diagnostic evaluation for a suspected condition
identify whether if it is screening test or diagnostic test:
large grp -
single subject -
large grp - screening
single subject - doagnostic
identify whether if it is screening test or diagnostic test:
asymptomatic -
suggestive clinical picture -
asymptomatic - screening
suggestive clinical picture - diagnostic
identify whether if it is screening test or diagnostic test:
it is not costly
screening
identify whether if it is screening test or diagnostic test:
it is for the basis for treatment
diagnostic
identify whether if it is screening test or diagnostic test:
it is conclusive
diagnostic
identify whether if it is screening test or diagnostic test:
it is not accurate
screening
briefly explain the types of screening test
- mass
non selective, large scale, whole population grp covid) - high risk
selective screening, only those who are at high risk - multiphasic
multiple screening, application of 2 or more screening test in combination to a large no. of ppl at one time (blood test, physical examination, nutritional evaluation, cancer screening test)
briefly explain the population approach and high risk strategy
popu approach
- not cost effective: every1 is required as long as u r with the infected person
- large chance to reduce disease incidence
- potential to alter the root cause of disease
- small benefit to indiv
- poor subject motivation
high risk strategy
- cost effective
- fails to deal w root cause of disease
- intervention appropriate to indiv (to find how we got hawa)
- subject motivates
- small chance in reducing the disease incidence
benefits and limitations of screening
benefits
- improve prognosis for some cases detected
- less radical treatment which cures early cases
-reassurance for those w -ve results
limitations
- hazards of screening (venipuncture, radiation)
- resources cost
- false assurance for those with false negative results
- anxiety to those with false positive results
define:
prognosis -
increase of prognosis -
prognosis - improvement of patient
increase of prognosis - patient will get well
briefly explain the criteria for successful screening test
- disease criteria
- present in population screened
- high burden and of high public health concern
- screening and intervention must improve outcome
- known natural history of the disease - test criteria
- simple and inexpensive
- cost effective
- acceptable to subjects and providers
- reliable
- exit strategy
- valid
- v. safe
briefly explain
criteria for successful screening test: reliability
repeatability, reducibility, precision - results r repeated
same results when test repeated in same target indiv in the same setting
briefly explain
criteria for successful screening test: cause of unreliability
own SOP/ protocol:
Standard Operating Procedures or testing protocols = intro inconsistencies and errors
observer variation:
diff in how technicians/ observes interpret, perform or score the screening test = variations in same subject
subject variation:
fluctuations in biomarker levels, physiological response or disease progression rates
technical method error variation:
errors or variation in the technical methods (sample collection, handling process, calibration, machine, temp fluctuations)
briefly explain
criteria for successful screening test: acceptability
test shld not be
- painful
- unsafe
- discomforting/ embarrassing
- socially/ believes not accepted
briefly explain
criteria for successful screening test: validity
able to distinguish btwn who has the disease and who does not
yield
sensitivity
specificity
predictive value
briefly explain the efficiency of a screening test
POSITIIVE
w disease & +ve test = true positive
w/o disease & +ve test = false positive
NEGATIVE
w disease & -ve test = false negative
w/o disease & -ve test = true negative
TOTAL
true positive + false negative = total of unknown cases of disease
false positive + true negative = total person w/o disease
draw ms danna’s table out and write out all the formulas
-
sensitivity =
specificity =
PPV =
NPV =
sensitivity = have sick
specificity = no sick
PPV = positive predictive value
NPV = true negative value
true or false:
PPV and NPV is sometimes inverse proportional
false - always
what are the 2 simultaneous testing
Net Sensitivity Rate
Net Specificity Rate
