Types of Studies by content
In addition to categorization by methodology,
studies can be characterized by content. Most articles under review can be
placed into one of the following categories: evaluation of a new therapy,
evaluation of a new diagnostic test, determination of the etiology of a
condition or prediction of the outcome, or natural course of a condition. Each
of these categories has different criteria for scientific review.
For a new therapy, some of the main issues
include the following:
• Results - The magnitude of treatment
effect and precision of the measurement
• Validity - Was there randomization
into treatment groups, accounting for all study patients, blinding of
participants and personnel, equality of treatment groups at baseline
• Impact - Applicability of results,
benefits versus risk and cost
For a new diagnostic test, some of the main
issues include the following:
• Test results - The presentation of
likelihood ratios and the receiver operating characteristic (ROC) curve
• Validity - Was there blind and
independent comparison to an accepted criterion ("gold") standard,
was the test applied to a wide patient spectrum, what was the effect of
performing the criterion standard, ease of test replication
• Impact - Patient applicability,
effect of clinical management of the patient's condition, effect on patient
care
For a study of the etiology of condition, some
of the main issues include the following:
• Results - Strength of exposure to
outcome, precise risk estimate
• Validity - Group similarity other
than the variable (exposure) of interest, same exposure measurements, strong
temporal relationship, adequate follow-up
• Impact - Results apply to patient
population, magnitude of risk
For a study of the prediction of outcome, some
of the main issues include the following:
• Results - Magnitude of outcome
likelihood, precision of likelihood estimate
• Validity - Representative patient
sample, sufficient follow-up, use of unbiased and objective outcome criteria
Impact - Equivalent patient population for
comparison, effect on therapy choice