====== Primary study ======
Primary [[study]] can observe the patient [[evolution]] after [[therapy]] ([[observational study]]) or if the investigator performs an intervention ([[interventional study]]). The case series is a descriptive and [[noncomparative study]], while the [[cross-sectional study]] and [[randomized clinical trial]]s are analytical and comparative studies.

[[Descriptive study]] or [[Noncomparative study]].

[[Analytical study]] or [[Comparative study]]:

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