Primary care

Randomised comparison of three methods of administering a screening questionnaire to elderly people: findings from the MRC trial of the assessment and management of older people in the community

Liam Smeeth, clinical lecturer in epidemiology, ^a Astrid E Fletcher, professor of epidemiology and ageing, ^a Susan Stirling, research fellow, ^a Maria Nunes, research officer, ^b Elizabeth Breeze, lecturer, ^a Edmond Ng, research fellow, ^a Christopher J Bulpitt, professor of geriatric medicine, ^b Dee Jones, principal research fellow. ^c

^a Centre for Ageing and Public Health, London School of Hygiene and Tropical Medicine, London WC1E 7HT, ^b Section of Care of the Elderly, Imperial College, Faculty of Medicine, Hammersmith Campus, London W12 0NN, ^c Research Team for Care of Elderly People, University Department of Geriatric Medicine, University of Wales College of Medicine, Cardiff CF64 2XX

Correspondence to: L Smeeth liam.smeeth{at}lshtm.ac.uk

Objective: To compare three different methods of administering a brief screening questionnaire to elderly people: post, interview by lay interviewer, and interview by nurse.
Design: Randomised comparison of methods within a cluster randomised trial.
Setting: 106 general practices in the United Kingdom.
Participants: 32 990 people aged 75 years or over registered with participating practices.
Main outcome measures: Response rates, proportion of missing values, prevalence of self reported morbidity, and sensitivity and specificity of self reported measures by method of administration of questionnaire for four domains.
Results: The response rate was higher for the postal questionnaire than for the two interview methods combined (83.5% v 74.9%; difference 8.5%, 95% confidence interval 4.4% to 12.7%, P<0.001). The proportion of missing or invalid responses was low overall (mean 2.1%) but was greater for the postal method than for the interview methods combined (4.1% v 0.9%; difference 3.2%, 2.7% to 3.6%, P<0.001). With a few exceptions, levels of self reported morbidity were lower in the interview groups, particularly for interviews by nurses. The sensitivity of the self reported measures was lower in the nurse interview group for three out of four domains, but 95% confidence intervals for the estimates overlapped. Specificity of the self reported measures varied little by method of administration.
Conclusions: Postal questionnaires were associated with higher response rates but also higher proportions of missing values than were interview methods. Lower estimates of self reported morbidity were obtained with the nurse interview method and to a lesser extent with the lay interview method than with postal questionnaires.