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# Pragmatic and explanatory trials

- Concept

An explanatory trial asks whether something can work under ideal conditions; a pragmatic one, whether it works in everyday practice with real patients.

Updated Nov 13, 2026

## Key points

- Explanatory = efficacy (can it work?); pragmatic = effectiveness (does it work in real life?).
- Pragmatic trials have broad inclusion criteria, flexible delivery and intention-to-treat analysis.
- The effect is usually smaller in pragmatic trials (real adherence, more varied patients) but more applicable.
- Very useful for non-drug interventions: surgery, rehabilitation, education, service organisation.
- It is a continuum: the PRECIS-2 tool describes it across several domains.

## What it is

An explanatory trial measures efficacy: the effect under ideal conditions, with selected patients, expert centres, monitored adherence and precise intermediate outcomes. A pragmatic trial measures effectiveness: the effect in routine practice, with patients like those in any clinic, ordinary staff and outcomes that matter to patients. These are not two closed boxes but a continuum, and each design sits somewhere on it domain by domain.

## Worked example

- Pulmonary rehabilitation programme. Explanatory trial: selected patients, 95 % attendance; admissions at 1 year: 20 % control versus 10 %.
- Explanatory: ARR = 20 − 10 = 10 points; NNT = 1 / 0.10 = 10.
- Pragmatic trial in primary care centres, 60 % attendance: 20 % versus 14 %.
- Pragmatic: ARR = 20 − 14 = 6 points; NNT = 1 / 0.06 = 16.7, rounded up to 17.
- Reading: the programme can work (efficacy), but in real practice 17 people, not 10, must be treated to prevent one admission.

## Domains in which they differ (PRECIS-2 style)

| Domain | More explanatory | More pragmatic |
| --- | --- | --- |
| Participants | Strict criteria, no other diseases | Almost everyone who would be treated in practice |
| Setting and staff | Expert centres | Ordinary clinics |
| Intervention | Rigid protocol | Flexible, as it would be delivered in practice |
| Adherence | Monitored and reinforced | Usual |
| Outcome | Intermediate, precisely measured | Important to the patient |
| Analysis | Sometimes per protocol | Intention to treat |

## Markers

- Efficacy
- Effectiveness
- PRECIS-2
- ITT

## In practice

- Explanatory trials usually come before approval; pragmatic trials inform service and guideline decisions.
- Non-drug interventions depend on the clinician and the setting: there the pragmatic approach matters more.
- Some pragmatic trials use electronic health records to recruit and to measure outcomes.

## Common pitfalls

- Calling a trial ‘pragmatic’ when it has strict inclusion criteria and monitored adherence.
- Expecting the same effect in practice as in an explanatory trial.
- Thinking pragmatic means sloppy: randomisation and outcome measurement remain rigorous.

## Memory aid

Explanatory is the test track; pragmatic is the street. What works on the track must still be tried in traffic.

## Test yourself

Think of the answer, then tap the question to see it.

## What does an explanatory trial measure, and what does a pragmatic one measure?

The explanatory trial measures efficacy under ideal conditions; the pragmatic trial measures effectiveness in routine practice.

## Why is the effect usually smaller in a pragmatic trial?

Because it includes more varied patients, lower adherence and ordinary clinicians, which dilute the effect.

## Which type of analysis is typical of a pragmatic trial?

Intention-to-treat analysis, which keeps each patient in the assigned group even if they did not follow the intervention.

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## Connections

## Related 5

- [Randomised controlled trial](https://durgical.com/en/epidemiology/randomised-controlled-trial/)
- [Intention-to-treat analysis](https://durgical.com/en/epidemiology/intention-to-treat-analysis/)
- [Number needed to treat](https://durgical.com/en/epidemiology/number-needed-to-treat/)
- [Real-world evidence and comparative effectiveness](https://durgical.com/en/epidemiology/real-world-evidence-and-comparative-effectiveness/)
- [Cluster randomised trial](https://durgical.com/en/epidemiology/cluster-randomised-trial/)

[← All of epidemiology](https://durgical.com/en/epidemiology/)

Educational content on epidemiological and statistical methods; the examples use made-up numbers to teach the calculation. Not a clinical or legal guide: current Colombian rules are in the official sources.

Sources: [CONSORT 2025 Statement: updated guideline for reporting randomised trials](https://www.equator-network.org/reporting-guidelines/consort/) (EQUATOR Network, 2025); [Chapter 17: Intervention complexity](https://www.cochrane.org/authors/handbooks-and-manuals/handbook/current/chapter-17) (Cochrane, 2024); [Real-World Evidence](https://www.fda.gov/science-research/science-and-research-special-topics/real-world-evidence) (U.S. Food and Drug Administration, 2026).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/epidemiology/pragmatic-and-explanatory-trials/