Some Examples of Ontario Screening Programs
Ontario Screening Program Examples
● PKU
○ Genetic condition born with, missing enzyme that breaks down aa, will have
buildup, need little protein intake
● PAP test and cervical cancer
● Mammography and breast cancer
● Colon cancer
Screening worthwhile only if there is a critical point
● Multiple critical points also available for some
● X= critical points before which treatment works better
Screening test and diagnostic test
● Diagnosis
○ Process of identifying a disease, ex) lung cancer
○ Diagnosis may involve assessing symptoms, and signs from physical exam, lab
test, and radiology
○ Symptom= subjective disease evidence(felt by patient)
○ Sign= objective disease evidence (identified by physician)
, ● Steps to diagnosis
○ Result in screening test
○ Search for explanation of symptoms
Q) why not go straight to defective test/ procedure
A) expenses, time invasiveness, discomfort or unacceptable risk- benefit ratio given pre-test
probability(=pre-test assessment of probability that individual is sick)
Clinical diagnosis endpoint
● Start appropriate treatment(for treatable conditions)
● Contact tracing(infectious disease)
● Counseling paliation(terminal disease)
Screening and diagnostic test
● Screening and diagnostic test try to “rule out” or “rule in” disease
● Both do this by probability
● Want to use test which moves probability of disease to either 0% or 100%
● Same Methods used to assess test validity of screening and diagnostic test
● Want to be certain test accomplishes goals of distinguishing the probably ill form the
probably well
● To assess test performance, compare to best estimate of the truth or gold standard
● Gold standard i a test or procedure that we assume provide more definitive or
confirmatory results
Gold standard
● External source of truth. Regarding disease status
● May be another more invasive test
Ontario Screening Program Examples
● PKU
○ Genetic condition born with, missing enzyme that breaks down aa, will have
buildup, need little protein intake
● PAP test and cervical cancer
● Mammography and breast cancer
● Colon cancer
Screening worthwhile only if there is a critical point
● Multiple critical points also available for some
● X= critical points before which treatment works better
Screening test and diagnostic test
● Diagnosis
○ Process of identifying a disease, ex) lung cancer
○ Diagnosis may involve assessing symptoms, and signs from physical exam, lab
test, and radiology
○ Symptom= subjective disease evidence(felt by patient)
○ Sign= objective disease evidence (identified by physician)
, ● Steps to diagnosis
○ Result in screening test
○ Search for explanation of symptoms
Q) why not go straight to defective test/ procedure
A) expenses, time invasiveness, discomfort or unacceptable risk- benefit ratio given pre-test
probability(=pre-test assessment of probability that individual is sick)
Clinical diagnosis endpoint
● Start appropriate treatment(for treatable conditions)
● Contact tracing(infectious disease)
● Counseling paliation(terminal disease)
Screening and diagnostic test
● Screening and diagnostic test try to “rule out” or “rule in” disease
● Both do this by probability
● Want to use test which moves probability of disease to either 0% or 100%
● Same Methods used to assess test validity of screening and diagnostic test
● Want to be certain test accomplishes goals of distinguishing the probably ill form the
probably well
● To assess test performance, compare to best estimate of the truth or gold standard
● Gold standard i a test or procedure that we assume provide more definitive or
confirmatory results
Gold standard
● External source of truth. Regarding disease status
● May be another more invasive test
