Table 3

Comparison of methods used in Thorax series and Californian EPA reviews

Thorax seriesCalifornian EPA
General approachSystematic search of the literatureUpdate of previous EPA review
ScopeChildren onlyAll ages
Respiratory (including SIDS but not CF)All systems (including SIDS, respiratory and CF)
Inclusions and exclusionsEmphasis on groups of similar studiesInclusion of all, even isolated studies
Disease definitionSpecific outcomes distinguishedBroader groups of diseases
Community versus hospitalDistinguished where possibleUsually combined
Maternal and paternal smokingDistinguished where possibleRarely analysed separately
Prenatal and postnatal exposureRarely possible to distinguishRarely possible to distinguish
ConfoundingAddressed in meta-analysis where possibleDiscussed in text
Publication biasDiscussed and evaluated where possibleNot discussed
SummarisationEmphasis on meta-analysis, less narrativeMore narrative, selective use of meta-analysis3-150
Causal inferenceDiscussedDiscussed
Population attributable risk estimatesNot attemptedIncluded for USA and California
Experimental (chamber) studiesVery limited evidence in childrenLimited evidence, mainly in adults
MechanismsNot discussedDiscussed
  • SIDS = sudden infant death syndrome; CF = cystic fibrosis.

  • 3-150 Only used for asthma induction, including early wheezing illnesses.