title: [Missing data in the somatisation subscale of the scl-90-R due to a 'checklist effect': occurrence in different surveys and results of various imputation methods].
abstract: Item non-response is a potential threat to the validity of study results. Taking the somatisation subscale of the SCL-90-R as an example, we hypothesise a specific response pattern ("checklist-effect") that is characterised by symptom-free persons not checking the "not at all"-category. The present study analyses the extent and relevance of this postulated "checklist-effect". Our data is derived from a survey of n = 228 blue-collar workers who previously had filed applications for medical rehabilitation benefits (A1-study), and two additional surveys as well. We defined the "checklist-effect" by the following response pattern: (1) at least one missing value and (2) at least one valid item response and (3) no "not at all"-responses. Occurrence of the "checklist-effect" in the three datasets differed widely. 75 % of the responders in the A1-Study had complete data, 16.2 % a postulated "checklist-effect". Imputation of missing values under the assumption of a "checklist-effect" led to a reduction of missing data in the somatisation-subscale from 12.3 % to 0.4 %. Ignoring the "checklist-effect" would overestimate the symptom level. Possible explanations for the effect are discussed. However, the validity of this effect has yet to be proven via methodological studies.
authors.affiliation: Institut für Sozialmedizin, Universitätsklinikum Schleswig-Holstein, Campus Lübeck. oskar.mittag@sozmed.uni-luebeck.de
authors.forename: O
authors.initials: O
authors.lastname: Mittag
authors.forename: T
authors.initials: T
authors.lastname: Meyer
authors.forename: R
authors.initials: R
authors.lastname: Deck
authors.forename: T
authors.initials: T
authors.lastname: Kohlmann
authors.forename: C
authors.initials: C
authors.lastname: Matthis
authors.forename: I
authors.initials: I
authors.lastname: Schäfer
authors.forename: H
authors.initials: H
authors.lastname: Raspe
mesh_terms: D015982:Bias; D015897:Comorbidity; D003627:Data Interpretation, Statistical; D005260:Female; D005858:Germany / Q000453:epidemiology; D006801:Humans; D008297:Male; D001523:Mental Disorders / Q000175:diagnosis / Q000453:epidemiology / Q000523:psychology; D008875:Middle Aged; D010146:Pain / Q000175:diagnosis* / Q000453:epidemiology* / Q000523:psychology; D010147:Pain Measurement / Q000379:methods / Q000706:statistics & numerical data*; D010349:Patient Compliance; D010555:Personality Inventory / Q000592:standards*; D011569:Psychiatric Status Rating Scales / Q000592:standards*; D015203:Reproducibility of Results; D012650:Self Disclosure; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires / Q000592:standards*