Acute respiratory infection case definitions for young children: a systematic review of community-based epidemiologic studies in South Asia.
OBJECTIVE
To explore the variability in childhood acute respiratory infection case definitions for research in low-income settings where there is limited access to laboratory or radiologic investigations.


METHODS
We conducted a systematic review of community-based, longitudinal studies in South Asia published from January 1990 to August 2013, in which childhood acute respiratory infection outcomes were reported. Case definitions were classified by their label (e.g. pneumonia, acute lower respiratory infection) and clinical content 'signatures' (array of clinical features that would be always present, conditionally present or always absent among cases). Case definition heterogeneity was primarily assessed by the number of unique case definitions overall and by label. We also compared case definition-specific acute respiratory infection incidence rates for studies reporting incidence rates for multiple case definitions.


RESULTS
In 56 eligible studies, we found 124 acute respiratory infection case definitions. Of 90 case definitions for which clinical content was explicitly defined, 66 (73%) were unique. There was a high degree of content heterogeneity among case definitions with the same label, and some content signatures were assigned multiple labels. Within studies for which incidence rates were reported for multiple case definitions, variation in content was always associated with a change in incidence rate, even when the content differed by a single clinical feature.


CONCLUSIONS
There has been a wide variability in case definition label and content combinations to define acute upper and lower respiratory infections in children in community-based studies in South Asia over the past two decades. These inconsistencies have important implications for the synthesis and translation of knowledge regarding the prevention and treatment of childhood acute respiratory infection.
Centre for Global Child Health, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, Canada.|Division of Paediatric Medicine, Department of Paediatrics, University of Toronto and Hospital for Sick Children, Toronto, Canada.
Daniel E
DE
Roth
Centre for Global Child Health, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, Canada.|Dalla Lana School of Public Health, University of Toronto, Toronto, Canada.
Michelle F
MF
Gaffey
Centre for Global Child Health, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, Canada.
Evelyn
E
Smith-Romero
Centre for Global Child Health, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, Canada.|Dalla Lana School of Public Health, University of Toronto, Toronto, Canada.
Tiffany
T
Fitzpatrick
Centre for Global Child Health, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, Canada.|Dalla Lana School of Public Health, University of Toronto, Toronto, Canada.|Division of Infectious Diseases, Department of Paediatrics, University of Toronto and Hospital for Sick Children, Toronto, Canada.
Shaun K
SK
Morris
D000208:Acute Disease; D001208:Asia / Q000453:epidemiology; D002648:Child; D006801:Humans; D015994:Incidence; D011203:Poverty; D012107:Research Design; D012111:Residence Characteristics; D012141:Respiratory Tract Infections / Q000145:classification* / Q000150:complications / Q000175:diagnosis / Q000453:epidemiology*
South Asia; bronchiolitis; children; developing countries; diagnosis; epidemiology; pneumonia; respiratory infections