Epidemiology and Infection

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Epidemiology and Infection (2010), 138:264-269 Cambridge University Press
Copyright © Cambridge University Press 2009

Original Papers

Climate and infection

Recall errors in a weekly survey of diarrhoea in Guatemala: determining the optimal length of recall

S. N. ZAFARa1 c1, S. P. LUBYa2 and C. MENDOZAa3

a1 Aga Khan University, Karachi, Pakistan, & Jinnah Postgraduate Medical Center, Pakistan
a2 Centers for Disease Control and Prevention, Atlanta, GA, USA
a3 Universidad del Valle de Guatemala, Medical Entomology Research and Training Unit, Guatemala City, Guatemala
Article author query
zafar sn [PubMed]  [Google Scholar]
luby sp [PubMed]  [Google Scholar]
mendoza c [PubMed]  [Google Scholar]


We measured the recall error, optimal recall length and factors associated with diarrhoea in a weekly survey. Data was taken from a year-long randomized controlled trial in which characteristics of diarrhoeal episodes were recorded weekly. We labelled the recall period as days 1–6; day 1 being the day before the visit. Recall error was the percentage difference between the number of episodes reported to begin on a particular day and the mean for days 1 and 2. Generalized estimating equations were used to determine associations. Recall error was 37% on day 3 and 51% on day 5. The error was less in younger children (by 10%), severe episodes (by 29%) and when blood was present in the stool (by 18%). Diarrhoea was underreported when the recall period extended beyond 2 days. Surveys that use longer recall periods risk underestimating diarrhoea incidence and selectively capturing more severe episodes.

(Accepted June 29 2009)

(Online publication August 05 2009)

Key Words:Bias; diarrhoea; recall; survey


c1 Author for correspondence: Dr S. N. Zafar, M-79 Khayaban-e-Ittehad Phase 7 DHA, Karachi, Pakistan. (Email: zafar.nabeel@gmail.com)