TABLE 4-3 Matching the Clinical Question with the Appropriate Evidence

Type of Question

Example of Question

Type of Evidencea

Screening or early diagnosis

Is prostate-specific antigen screening for the detection of prostate cancer in low-risk populations effective in reducing mortality?



Does early diagnosis by use of a PETb scan result in improved cognitive ability for patients with Alzheimer’s disease?



Does smoking cause lung cancer?

Cohort studies, case-control studies

Diagnostic accuracy

Does a PET scan diagnose Alzheimer’s disease more accurately than a standard clinical evaluation?

Case series (RCTs desirable but unlikely)


What is the likelihood for fertility loss in a premenopausal woman receiving chemotherapy for breast cancer?

RCTs, cohort studies


How long do patients remain insulin independent after pancreatic islet cell transplantation for Type I diabetes mellitus?

Cohort studies, case series

Preventive or therapeutic effectivenessc

Is bevacizumab (Avastin) as effective as ranibizumab (Lucentis) in delaying the progression of acute macular degeneration?



How does surgical implantation of an artificial lumbar disc compare with lumbar spinal fusion for pain reduction in patients with degenerative disc disease?



Is external beam radiation more effective than watchful waiting in reducing mortality from prostate cancer?


Safety or potential harm

What proportion of postmenopausal women receiving calcium and vitamin D supplements develop kidney stones?

RCTs, cohort studies, case-control studies


Is robotic-assisted radical prostatectomy more likely to lead to urinary incontinence than laparoscopicic-assisted radical prostatectomy?

RCTs, cohort studies, case-control studies

aSystematic reviews of the “best” evidence are more reliable than evidence from a single study, regardless of the clinical question being asked.

bPET = positron emission tomography.

cIncludes drugs, devices, procedures, physical therapy, counseling, behavior change, and systems change in head-to-head comparisons and comparisons with standard interventions, placebo or sham treatments, or no intervention.

SOURCE: Adapted from the work of Dickersin (2007).

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