Objective: Clinical studies are often facing missing data. Data can be missing for various reasons, for example, patients moved, certain measurements are only administered in high-risk groups, and patients are unable to attend clinic because of their health status. There are various ways to handle these missing data (e.g., complete cases analyses, mean substitution). Each of these techniques potentially influences both the analyses and the results of a study. The first aim of this structured review was to analyze how often researchers in the field of otorhinolaryngology/head & neck surgery report missing data. The second aim was to systematically describe how researchers handle missing data in their analyses. The third aim was to provide a solution on how to deal with missing data by means of the multiple imputation technique. With this review, we aim to contribute to a higher quality of reporting in otorhinolaryngology research.
Design: Clinical studies among the 398 most recently published research articles in three major journals in the field of otorhinolaryngology/head & neck surgery were analyzed based on how researchers reported and handled missing data.
Results: Of the 316 clinical studies, 85 studies reported some form of missing data. Of those 85, only a small number (12 studies, 3.8%) actively handled the missingness in their data. The majority of researchers exclude incomplete cases, which results in biased outcomes and a drop in statistical power.
Conclusions: Within otorhinolaryngology research, missing data are largely ignored and underreported, and consequently, handled inadequately. This has major impact on the results and conclusions drawn from this research. Based on the outcomes of this review, we provide solutions on how to deal with missing data. To illustrate, we clarify the use of multiple imputation techniques, which recently became widely available in standard statistical programs.
1Department of Otorhinolaryngology and Head & Neck Surgery, 2Department of Epidemiology, Leiden University Medical Center, Leiden, The Netherlands; 3Department of Developmental Psychology, Leiden University, Leiden, The Netherlands; 4Dutch Foundation for the Deaf and Hard of Hearing Child, Amsterdam, The Netherlands; and 5Leiden Institute for Brain and Cognition, Leiden, The Netherlands.
The authors have no conflicts of interest to disclose.
Received March 22, 2016; accepted May 13, 2016.
Address for correspondence: Anouk P. Netten, Department of Otorhinolaryngology and Head & Neck Surgery, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands. E-mail: firstname.lastname@example.org