Background: The objectives of this systematic review are to examine how researchers report missing data in questionnaires and to provide an overview of current methods for dealing with missing data.
Methods: We included 262 studies published in 2010 in 3 leading epidemiologic journals. Information was extracted on how missing data were reported, types of missing, and methods for dealing with missing data.
Results: Seventy-eight percent of the studies lacked clear information about the measurement instruments. Missing data in multi-item instruments were not handled differently from other missing data. Complete-case analysis was most frequently reported (81% of the studies), and the selectivity of missing data was seldom examined.
Conclusions: Although there are specific methods for handling missing data in item scores and in total scores of multi-item instruments, these are seldom applied. Researchers mainly use complete-case analysis for both types of missing, which may seriously bias the study results.
From the aDepartment of Epidemiology and Biostatistics, VU University Medical Center, Amsterdam, The Netherlands; bEMGO Institute for Health and Care Research, Amsterdam, The Netherlands; cDepartment of Methodology and Applied Biostatistics, Faculty of Earth and Life Sciences, Institute for Health Sciences, VU University, Amsterdam, The Netherlands; and dDepartment of Public Health, University Medical Center Groningen, Groningen, The Netherlands.
Submitted 12 October 2011; accepted 24 February 2012; posted 11 May 2012.
Supported by EMGO Institute of Health and Care Research. The authors reported no other financial interests related to this research.
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Correspondence: Iris Eekhout, Department of Epidemiology and Biostatistics, VU University Medical Center (room MF D439), Van der Boechorststraat 7, 1081 BT, Amsterdam, The Netherlands. E-mail: firstname.lastname@example.org.