Table of Contents

Prospective observational study

An observational study, often longitudinal in nature, for which the consequential outcomes of interest occur after study commencement (including the creation of a study protocol and analysis plan, and study initiation).

Classification

Prospective observational studies collect data forward in time without intervening. They are a key design for real-world clinical research.

🧠 Main Subtypes of Prospective Observational Studies

1. Prospective Cohort Study

  • Follows a defined group (cohort) over time.
  • Groups may be based on exposure or risk.
  • Outcomes are observed without intervention.
  • Example: 100 elderly patients undergoing neurosurgery for brain metastases, followed for complications.

2. Registry-Based Prospective Study

  • Data collected through multi-institutional registries.
  • Reflects real-world practice.
  • May include various exposures and outcomes.
  • Example: Registry of CNS metastases patients receiving different treatments.

3. Prospective Case Series

  • Descriptive follow-up of similar patients.
  • No comparison group.
  • Example: Series of patients undergoing awake craniotomy.

4. Prospective Case-Control Study

  • Participants selected based on future outcomes.
  • Past exposures compared retrospectively.
  • Often nested within a cohort.
  • Example: Patients who develop radiation necrosis vs. those who don’t.

5. Prospective Longitudinal Study

  • Repeated measures over time.
  • Focus on temporal evolution (e.g., function, biomarkers).
  • Example: Tracking cognition for 12 months after surgery.

📊 Summary Table

Subtype Groups Compared? Outcome Over Time? Intervention? Typical Use
Prospective Cohort study Yes Yes No Exposure-outcome analysis
Registry-Based study Optional Yes No Real-world multicenter data
Prospective Case Series No Yes No Descriptive outcomes
Prospective Case-Control Yes Retro from outcome No Risk factors (nested case-control)
Prospective Longitudinal study No/Optional Yes (repeated) No Tracking change over time