title: Random and systematic errors in case-control studies calculating the injury risk of driving under the influence of psychoactive substances.
abstract: Between 2006 and 2010, six population based case-control studies were conducted as part of the European research-project DRUID (DRiving Under the Influence of Drugs, alcohol and medicines). The aim of these case-control studies was to calculate odds ratios indicating the relative risk of serious injury in car crashes. The calculated odds ratios in these studies showed large variations, despite the use of uniform guidelines for the study designs. The main objective of the present article is to provide insight into the presence of random and systematic errors in the six DRUID case-control studies. Relevant information was gathered from the DRUID-reports for eleven indicators for errors. The results showed that differences between the odds ratios in the DRUID case-control studies may indeed be (partially) explained by random and systematic errors. Selection bias and errors due to small sample sizes and cell counts were the most frequently observed errors in the six DRUID case-control studies. Therefore, it is recommended that epidemiological studies that assess the risk of psychoactive substances in traffic pay specific attention to avoid these potential sources of random and systematic errors. The list of indicators that was identified in this study is useful both as guidance for systematic reviews and meta-analyses and for future epidemiological studies in the field of driving under the influence to minimize sources of errors already at the start of the study.
authors: SWOV, Institute for Road Safety Research, Duindoorn 32, 2262 AR Leidschendam, The Netherlands. sjoerd.houwing@swov.nl
authors: Sjoerd
authors: S
authors: Houwing
authors: Marjan
authors: M
authors: Hagenzieker
authors: René P M
authors: RP
authors: Mathijssen
authors: Sara-Ann
authors: SA
authors: Legrand
authors: Alain G
authors: AG
authors: Verstraete
authors: Tove
authors: T
authors: Hels
authors: Inger Marie
authors: IM
authors: Bernhoft
authors: Kirsten Wiese
authors: KW
authors: Simonsen
authors: Pirjo
authors: P
authors: Lillsunde
authors: Donata
authors: D
authors: Favretto
authors: Santo D
authors: SD
authors: Ferrara
authors: Marija
authors: M
authors: Caplinskiene
authors: Kris L L
authors: KL
authors: Movig
authors: Karel A
authors: KA
authors: Brookhuis
mesh_terms: D000063:Accidents, Traffic / Q000706:statistics & numerical data*; D001334:Automobile Driving; D015982:Bias; D016022:Case-Control Studies; D003627:Data Interpretation, Statistical; D006801:Humans; D016017:Odds Ratio; D011619:Psychotropic Drugs / Q000009:adverse effects*; D018570:Risk Assessment; D015983:Selection Bias; D014947:Wounds and Injuries / Q000453:epidemiology*
chemical_list: D011619:Psychotropic Drugs