title: Measuring academic performance for healthcare researchers with the H index: which search tool should be used?
abstract: OBJECTIVE
  To compare H index scores for healthcare researchers returned by Google Scholar, Web of Science and Scopus databases, and to assess whether a researcher's age, country of institutional affiliation and physician status influences calculations.
  
  
  METHODS
  One hundred and ninety-five Nobel laureates in Physiology and Medicine from 1901 to 2009 were considered. Year of first and last publications, total publications and citation counts, and the H index for each laureate were calculated from each database. Cronbach's alpha statistics was used to measure the reliability of H index scores between the databases. Laureate characteristic influence on the H index was analysed using linear regression.
  
  
  RESULTS
  There was no concordance between the databases when considering the number of publications and citations count per laureate. The H index was the most reliably calculated bibliometric across the three databases (Cronbach's alpha = 0.900). All databases returned significantly higher H index scores for younger laureates (p < 0.0001). Google Scholar and Web of Science returned significantly higher H index for physician laureates (p = 0.025 and p = 0.029, respectively). Country of institutional affiliation did not influence the H index in any database.
  
  
  CONCLUSIONS
  The H index appeared to be the most consistently calculated bibliometric between the databases for Nobel laureates in Physiology and Medicine. Researcher-specific characteristics constituted an important component of objective research assessment. The findings of this study call to question the choice of current and future academic performance databases.
authors.affiliation: Department of Surgery and Cancer, Imperial College London, St. Mary's Hospital, London, UK. vanash.patel06@imperial.ac.uk
authors.forename: Vanash M
authors.initials: VM
authors.lastname: Patel
authors.forename: Hutan
authors.initials: H
authors.lastname: Ashrafian
authors.forename: Alex
authors.initials: A
authors.lastname: Almoudaris
authors.forename: Jonathan
authors.initials: J
authors.lastname: Makanjuola
authors.forename: Chiara
authors.initials: C
authors.lastname: Bucciarelli-Ducci
authors.forename: Ara
authors.initials: A
authors.lastname: Darzi
authors.forename: Thanos
authors.initials: T
authors.lastname: Athanasiou
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D015706:Bibliometrics; D035843:Biomedical Research; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009613:Nobel Prize; D011643:Publishing / Q000706:statistics & numerical data*; D015203:Reproducibility of Results