title: Significant discrepancies were found in pooled estimates of searching with Chinese indexes versus searching with English indexes.
abstract: OBJECTIVE
  To assess the impact of search strategies for a different language on systematic review results, using English index searches versus Chinese index searches for Chinese literature pertaining to cerebral palsy (CP) as an example.
  
  
  METHODS
  We conducted two parallel searches with the same search strategy. Both searches looked for studies published in the Chinese language that examined risk factors for CP. The first was conducted in standard English indexes and the second was in standard Chinese indexes. We compared the results using the two searches using a Z-test. Egger's test and Begg's test were used to assess the potential publication bias.
  
  
  RESULTS
  Using the English indexes, nine studies were identified. Using the identical search and inclusion/exclusion criteria in the Chinese indexes, 17 studies were returned. The association between intracranial hemorrhage and CP was much stronger in the studies found in the search by the English indexes (odds ratio [OR] 61.73, 95% confidence interval (CI) 19.48-195.61) than the results from studies identified by the Chinese indexes (OR 9.57, 95% CI 2.42-37.88). The association between hypertension and CP was not significant in studies found using the English indexes (OR 1.67, 95% CI 0.34-8.30) but was significant in studies identified by searching the Chinese indexes (OR 2.25, 95% CI 1.06-4.77). Egger's test suggested that, for the risk factor of preterm birth, some small studies with negative results might have been missed by the search using the English indexes (Egger's test: P = 0.00).
  
  
  CONCLUSIONS
  Searching Chinese literature using English indexes has the potential to fail to identify a substantial number of publications. This bias can result in significant discrepancies in the pooled estimates of risk factors for CP.
authors.affiliation: Department of Medical Records Information, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410000, China; OMNI Research Group, Department of Obstetrics and Gynecology, University of Ottawa Faculty of Medicine, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada; Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada; School of Public Health, Central South University, 87 Xiangya Road, Changsha, Hunan 410000, China; Institute for Hospital Management of Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410000, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Xue
authors.affiliation: OMNI Research Group, Department of Obstetrics and Gynecology, University of Ottawa Faculty of Medicine, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada; Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada; Department of Nephrology, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410000, China.
authors.forename: Wenhang
authors.initials: W
authors.lastname: Chen
authors.affiliation: School of Public Health, Central South University, 87 Xiangya Road, Changsha, Hunan 410000, China.
authors.forename: Lizhang
authors.initials: L
authors.lastname: Chen
authors.affiliation: OMNI Research Group, Department of Obstetrics and Gynecology, University of Ottawa Faculty of Medicine, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada; Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada.
authors.forename: Laura
authors.initials: L
authors.lastname: Gaudet
authors.affiliation: Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada; Department of Medicine, Faculty of Medicine, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada; Faculty of Medicine, School of Epidemiology, Public Health, and Preventive Medicine, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Moher
authors.affiliation: OMNI Research Group, Department of Obstetrics and Gynecology, University of Ottawa Faculty of Medicine, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada; Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada; Faculty of Medicine, School of Epidemiology, Public Health, and Preventive Medicine, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada.
authors.forename: Mark
authors.initials: M
authors.lastname: Walker
authors.affiliation: OMNI Research Group, Department of Obstetrics and Gynecology, University of Ottawa Faculty of Medicine, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada; Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada; School of Public Health, Central South University, 87 Xiangya Road, Changsha, Hunan 410000, China; Faculty of Medicine, School of Epidemiology, Public Health, and Preventive Medicine, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada. Electronic address: swwen@ohri.ca.
authors.forename: Shi Wu
authors.initials: SW
authors.lastname: Wen
mesh_terms: D002547:Cerebral Palsy / Q000209:etiology*; D006801:Humans; D007802:Language; D015201:Meta-Analysis as Topic; D017594:Publication Bias; D012107:Research Design; D012196:Review Literature as Topic; D012307:Risk Factors; D057386:Search Engine
keywords: Cerebral palsy; Chinese; Literature searching; Meta-analysis; Risk factor; Systematic review