For healthcare professionals only

Endgames Statistical Question

Allocation concealment versus blinding in randomised controlled trials

BMJ 2013; 347 doi: (Published 13 September 2013) Cite this as: BMJ 2013;347:f5518
  1. Philip Sedgwick, reader in medical statistics and medical education
  1. 1Centre for Medical and Healthcare Education, St George’s, University of London, London, UK
  1. p.sedgwick{at}

Researchers investigated the effectiveness of the provision of whole food to enhance the completion of treatment for tuberculosis. A parallel group randomised controlled trial study design was used. The intervention was a nutritious culturally appropriate daily meal (weeks 1-8) and food package (weeks 9-32). Control treatment was nutritional advice alone at enrolment. Both intervention and control groups received standard care throughout the study period. The primary outcome was completion of treatment (clearance of acid fast bacilli from the sputum after treatment or the completion of eight months of treatment, or both).1

Participants were 270 adults (aged over 18 years) with previously untreated and newly diagnosed pulmonary tuberculosis, recruited from primary care clinics in Dili, Timor-Leste. Participants were randomised to treatment group after they had started standard tuberculosis treatment. The randomisation sequence was computer generated. Allocation concealment was ensured by the use of sequentially numbered, opaque, sealed envelopes. An independent observer, blinded to the allocated treatment, assessed the primary outcome.

There was no significant difference between treatment groups in the proportion of participants who achieved the primary outcome (intervention 76% …

View Full Text

Log in

Log in through your institution


* For online subscription