Which of the following is the correct sequence of steps in a Randomized Controlled Trial (RCT)?

Explanation

## Correct Answer: B. Randomisation → Manipulation → Follow-up → Assessment The correct sequence of an RCT follows a strict methodological order that ensures validity and minimizes bias. **Randomisation** must occur first—after baseline eligibility assessment but before any intervention—to ensure unbiased allocation of participants to treatment and control groups. This random allocation breaks the link between participant characteristics and group assignment, preventing selection bias. **Manipulation** (the intervention itself) follows randomisation; participants receive their assigned treatment. **Follow-up** comes next, during which researchers monitor adherence, collect safety data, and track outcomes over the study period. Finally, **Assessment** of outcomes occurs at predetermined endpoints to measure the intervention's efficacy. This sequence is critical because it prevents knowledge of group assignment from influencing baseline measurements, ensures comparable groups at baseline, and allows blinded outcome assessment. In Indian RCTs (e.g., RNTCP trials, vaccine efficacy studies), this sequence is mandated by ICMR guidelines and ethical review boards. Deviating from this order introduces bias: assessing before randomisation risks selection bias, manipulating before randomisation violates the randomisation principle, and assessing before follow-up prevents adequate outcome measurement. ## Why the other options are wrong **A. Manipulation → Assessment → Follow-up → Randomisation** — This sequence is fundamentally flawed because manipulation occurs before randomisation, violating the core principle of RCTs. Randomisation must precede intervention to ensure unbiased group allocation. Assessing before randomisation introduces selection bias. This sequence would render the trial non-randomised and observational, defeating the purpose of an RCT. **C. Assessment → Randomisation → Follow-up → Manipulation** — While assessment before randomisation is acceptable (baseline characteristics), manipulation must follow randomisation, not precede follow-up. This sequence places follow-up before the intervention, which is illogical—you cannot follow up on an intervention that hasn't been delivered yet. This violates the temporal logic of RCT design. **D. Follow-up → Manipulation → Assessment → Randomisation** — This sequence is completely reversed and nonsensical. Randomisation must occur first to allocate participants; follow-up cannot precede the intervention. Placing assessment before randomisation and randomisation last destroys the entire RCT framework. This represents a fundamental misunderstanding of RCT methodology. ## High-Yield Facts - **Randomisation** must occur FIRST (after baseline eligibility check) to ensure unbiased allocation and prevent selection bias in RCTs. - **Manipulation** (intervention delivery) follows randomisation; this temporal order is non-negotiable in RCT design. - **Follow-up** phase monitors adherence, safety, and intermediate outcomes during the intervention period. - **Assessment** of primary and secondary outcomes occurs at pre-specified endpoints after adequate follow-up duration. - ICMR guidelines mandate this sequence for all RCTs conducted in India; deviation requires ethical justification and regulatory approval. ## Mnemonics **RAN-MAN-FAN-PLAN** **RAN**domisation → **MAN**ipulation → **FAN** Follow-up → **PLAN** Assessment. Memory hook: 'Randomise, Manipulate, Follow, then Plan your analysis.' **RMFA Sequence** **R**andomise → **M**anipulate → **F**ollow-up → **A**ssess. Think: 'Randomise first, then do everything else in order.' ## NBE Trap NBE commonly pairs RCT sequence questions with distractor options that reverse the order or place assessment before randomisation, exploiting students who confuse baseline assessment (which occurs before randomisation) with outcome assessment (which occurs after follow-up). The trap is conflating "assessment" as a single step rather than recognising baseline assessment precedes randomisation while outcome assessment follows follow-up. ## Clinical Pearl In Indian vaccine trials (e.g., rotavirus efficacy studies under RNTCP), strict adherence to this sequence is critical: eligible children are randomised first, then receive vaccine or placebo (manipulation), followed by surveillance visits (follow-up), and finally antibody titres or disease incidence are assessed (assessment). Any deviation compromises the trial's credibility and regulatory approval. _Reference: Park's Textbook of Preventive and Social Medicine (Ch. 10 - Research Methodology); ICMR Guidelines for Biomedical Research on Human Subjects_