Critical appraisal: a practical guide to judging medical research

Seen a claim that a drug or supplement works wonders and wondered if it's true? Critical appraisal is the skill that turns headlines into useful facts. You don’t need a PhD to spot questionable studies — you need a clear checklist and a bit of practice.

Start by asking one simple question: what type of study is this? Randomized controlled trials (RCTs) and systematic reviews sit higher on the evidence ladder than single case reports or industry press releases. If a claim is based on a small, uncontrolled study, treat it as preliminary, not proof.

Quick checklist to read a study fast

Use these five quick checks before you trust a headline or ad:

  • Question and population: Does the study ask something relevant to you? A study on young athletes may not apply to older patients with multiple conditions.
  • Design: RCT? Cohort? Case-control? Each design limits what you can conclude — RCTs can show causation, observational studies usually cannot.
  • Size and duration: Small studies and short follow-ups often miss rare harms or long-term issues. Bigger and longer usually mean more reliable results.
  • Outcome measures: Are they measuring real benefits (fewer hospitalizations, lives saved) or soft endpoints (lab numbers, symptom scores)? Real outcomes matter more.
  • Statistics and effect size: Look past p-values. Ask how big the benefit is in real terms — absolute risk reduction and number needed to treat tell you that.

One practical example: a study reports a 50% relative reduction in risk. That sounds huge until you see the absolute risk dropped from 2% to 1% — a 1% absolute reduction. Knowing that makes decision-making clearer.

Red flags and where to dig deeper

Watch for these warning signs: industry funding without clear conflict-of-interest statements, missing blinding, selective reporting of outcomes, and heavy reliance on surrogate markers. If the paper omits methods or has oddly high drop-out rates, be skeptical.

Where to check facts: trusted sources like PubMed, Cochrane Reviews, and clinical guidelines (e.g., NICE, WHO) summarize the best evidence. For drug safety and approvals, check regulators like FDA or EMA. For online pharmacy claims or product reviews, cross-check with official prescribing information and regulator warnings.

Final practical tip: apply findings to the person, not the paper. Ask: will this benefit the patient I’m thinking of? Do risks change based on age, other meds, or existing conditions? If you’re unsure, a short chat with a pharmacist or clinician who reads evidence regularly usually clears things up fast.

Use this guide the next time a flashy health headline pops up. It takes a few minutes to use these checks, and you’ll save time — and stress — down the road.