The structure of a clinical research study affects what can be concluded from its findings. Grimes and Schulz used a simple algorithm to classify research studies. The authors are from Family Health International in Research Triangle Park (Raleigh-Durham), North Carolina.
Did the investigator assign exposure(s)? |
Type of Study |
yes |
experimental |
no |
observational |
If experimental study, was there random allocation of subjects? |
Type of Study |
yes |
randomized controlled |
no |
nonrandomized controlled |
If observational study, is there a comparison (control) group? |
Type of Study |
yes |
analytical |
no |
descriptive |
If analytical study, how are cause and effect evaluated? |
Type of Study |
people exposed are followed to determine outcome |
cohort study |
people with outcome are studied to determine previous exposures |
case-control study |
exposures and outcomes determined at one time point |
cross-sectional study |
Subtypes of descriptive studies:
(1) case report (a single patient is described)
(2) case series report (two or more patients described)
ICD-10: ,