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Presented at a course on screening Faculty of Medicine, Riyadh on 06 March 2019. By Prof. Omar Hasan Kasule Sr. MB ChB (MUK), MPH (Harvard) DrPH (Harvard). Chairman, Institutional Review Board - KFMC
BENEFIT
vs HARM
} Mass screening for disease has advantages (benefits) and disadvantages
(harms).
} Benefits may be public (e.g. decreases health budget), private (benefit
some groups), or individual (protect individual health).
} Examples of benefits are: early detection followed by early treatment and
longer real survival.
} Examples of harms: longer psychological morbidity for untreatable
disease, unnecessary diagnostic and treatment procedures for false positive
disease, late diagnosis for false negative screen tests.
} In general, the benefit of screening must outweigh the harm. We are
ethically required to minimize the harm.
EXAMPLES
of BENEFITS of SCREENING PROGRAMS
} TB screening has a public benefit in that cases of infectious disease are
identified and are treated so that they pose no further danger to the public.
} HIV screening has a private benefit for insurance companies that adjust
their premiums and decide who to insure and who to exclude; the companies do
not share this information with the public or the individual screened.
} Screening may have a direct benefit to the individual by improving
prognosis, enabling earlier treatment with less radical therapy.
} Screening has psychological advantages. If negative it reassures.
EXAMPLES
of DISADVANTAGES of SCREENING - 1
} Screen-detected cases whose disease cannot be cured suffer from a longer
period of morbidity.
} Borderline lesions may be over-treated when if left alone they would not
progress to serious disease.
} Over-diagnosis and under-diagnosis.
} The results of genetic screening may have several adverse consequences
such as stigmatization, discrimination, abortion, and psychological stress.
} Screening programs may create an ethical issue by diverting resources
away from other health programs.
} Failure to obtain informed consent is a serious ethical violation.
} Screening without prior consultation is a serious ethical violation
because returning results can be psychologically traumatic.
EXAMPLES
of DISADVANTAGES of SCREENING - 2
} Screening tests have their own risks and costs. e.g. colonoscopy may
cause intestinal perforation.
} False-negative results create a false sense of security. False negative
patients get false reassurance that will discourage them from seeking care when
early symptoms appear.
} False positive results create unnecessary distress. False-positive
patients live with anxiety longer than necessary. False positives undergo
unnecessary medical intervention.
} True negative effects may cause complacency.
} True positive results lead to worry and anxiety.
LACK
of ACCESS to SCREENING AMONG the LOW SOCIO-ECONOMIC CLASS
} Low awareness/knowledge of screening benefits and do not seek it or
accept it if offered.
} No access to screening sites because they are too far away from their
residence.
} They cannot afford the cost of obtaining screening.
} They have no access to treatment even if they get screened positive, so why
bother?
} Should mass screening for some diseases be free and mandatory?
COMMON
SCREENING PROGRAMS
} Pap smear for cervical cancer.
} Mammography for breast cancer.
} Colonoscopy for colon cancer.
} PSA for prostate cancer.
OTHER
SCREENING PROGRAMS
} PPD for tuberculosis.
} Beck depression for depression.
} Ultrasound for fetal abnormalities.
} Ophthalmoscopy for diabetic retinopathy.
} Vision and hearing screening in schools.
MISINTERPRETATION
of TEST RESULTS
} Lead-time bias: Apparent increase in survival due to earlier screen
detection of the disease without change in time of death.
} Length-time bias: slower going less dangerous disease is more likely to
be detected because it stays around longer.