Pragmatic trial

Trials sit on a spectrum. An explanatory trial asks whether a treatment can work under ideal conditions: narrow eligibility, specialist centres, tightly controlled dosing, a placebo comparator, frequent scans. A pragmatic trial asks whether it does work in practice: broad eligibility including the older and sicker patients who make up most of the clinic, usual care as the comparator, delivery by the usual staff, follow-up through routine records, and an outcome such as survival or hospital admission rather than a scan-defined surrogate. The PRECIS-2 wheel scores a design on nine such dimensions. Pragmatic trials tend to be large, cheap per patient and publicly funded, because the interventions they test (a generic drug, an exercise programme, a screening schedule, a shorter course) rarely have a commercial sponsor.

The corpus examples are mostly academic. CHALLENGE randomised 889 colon cancer patients after chemotherapy to a coached exercise programme or health-education materials, delivered by physical activity consultants across five countries over three years, and found better disease-free and overall survival; it tested a service, not a molecule. Add-Aspirin randomises 11,000 patients across four cancers in the United Kingdom, Ireland and India to a generic drug or placebo for five years, with publicly funded infrastructure and broad eligibility; it keeps a placebo, so it is pragmatic in scale and setting rather than in every dimension. BWEL delivered a two-year weight-loss programme to more than 3,000 women by telephone. The Indian cluster-randomised screening trials in Kerala, Mumbai and Osmanabad, run through primary health workers in the communities they served, are pragmatic trials at population scale.

The trade-off is precision for relevance. Usual care varies between sites and drifts over a long trial, adherence is lower than in a tightly run trial, and outcomes drawn from routine records are less complete than trial-collected ones, all of which pull the result towards no difference. A pragmatic trial that shows a benefit is therefore persuasive; one that shows none may have diluted a real effect. Pragmatic and explanatory answers are both needed, in that order for a new drug and often in the reverse order for a change in how care is organised.