Missing data due to a 'checklist misconception-effect'.

Objectives: To analyze the extent and relevance of a postulated "checklist misconception-effect" (a specific response pattern characterized by symptom-free persons not checking the "not at all"-category).

Methods: Our data is derived from a survey of blue collar workers (n = 228) who previously had filed in applications for medical rehabilitation benefits. We defined the "checklist misconception-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.

Results: 75% of the responders had complete data, 16.2% a postulated 'checklist misconception-effect'. Substantial co-variations with socio-demographic characteristics or health status indicators could not be found. Additional imputation of missing values under the assumption of a "checklist misconception-effect" led to a reduction of missing data in the somatisation-subscale score from 12.3% to 0.4% compared to a simple manual-based calculation. Correlation with various external criteria (general health perception, level of functioning, depression) remained unchanged.

Conclusions: Ignoring the "checklist misconception-effect" would overestimate symptom load. However, the validity of this effect has still to be proven in methodological studies.