Retrospective Study

**What it means:** A retrospective study looks **backward in time** at existing data — reviewing past patient records, genetic test results, and clinical outcomes to find patterns. It's less rigorous than a prospective study (which follows patients forward from the start) but is faster, cheaper, and can be done with already-collected data. **The 2025 paper** mentioned in the search results used a retrospective design — collecting information from patients who were already diagnosed at the centre between 2019 and 2024, then searching the literature to summarize clinical features. This type of study is valuable for building the evidence base but can't prove causation on its own.