Modern medicine's gold-standard trial was born from sealed envelopes and random numbers
To test a new tuberculosis drug fairly in 1948, British researchers let chance — not doctors — decide who got it.
When the antibiotic streptomycin arrived, supplies were scarce and Britain had to decide who received it. The Medical Research Council turned that shortage into a rigorous experiment.
In its 1948 trial for pulmonary tuberculosis, patients were assigned to either streptomycin plus bed rest, or bed rest alone, using random sampling numbers — with the allocation hidden in sealed envelopes so no doctor could steer who got the drug. Designed with statistician Austin Bradford Hill, this concealment is what made the comparison genuinely fair.
The James Lind Library calls it a methodological landmark, widely cited as a model for the modern randomised controlled trial.
Randomising and concealing assignment cancels out bias from doctors unconsciously giving promising treatments to healthier patients.
That safeguard still underpins how new drugs are proven today.
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