Table 1.

Description of the study.

Study Types
  1. Clinical descriptive: a study in which the aim is to define a certain clinical feature such as a symptom, a laboratory or a clinical finding, or the disease course under different conditions

  2. Clinical hypothesis-testing: any human study in which the aim is testing a clinical hypothesis

  3. Pure epidemiology: any field survey in which the main aim is to search for the prevalence or incidence of the disease by formal, population-based methods

  4. Epidemiology—other: any epidemiologic study that is not a true population-based field survey. This group includes, among others, attempts at diagnostic and classification criteria

  5. Controlled drug trial: any controlled trial of a drug

  6. Drug use— other: any human drug study other than a controlled drug trial

  7. Mainly laboratory: any experimental study in humans that is not a genetic association study

  8. Genetic association: any study in which the association between a disease or disease phenotype and a genetic polymorphism or mutation was studied

  9. Animal studies: any study based on animal experimentation

  10. Other: any study that does not meet any of the descriptions above

Time Elements
  1. Cross-sectional study: in which the patients are seen/evaluated only once during the study period

  2. Longitudinal study (prospective or retrospective): in which a patient was followed by at least 2 patient visits during the study period

  3. Retrospective longitudinal study: surveying the fate of a cohort at the present time with a historical inception point in the past