title: Applying Computerized Adaptive Testing to the Four-Dimensional Symptom Questionnaire (4DSQ): A Simulation Study.
abstract: BACKGROUND
  Efficient screening questionnaires are useful in general practice. Computerized adaptive testing (CAT) is a method to improve the efficiency of questionnaires, as only the items that are particularly informative for a certain responder are dynamically selected.
  
  
  OBJECTIVE
  The objective of this study was to test whether CAT could improve the efficiency of the Four-Dimensional Symptom Questionnaire (4DSQ), a frequently used self-report questionnaire designed to assess common psychosocial problems in general practice.
  
  
  METHODS
  A simulation study was conducted using a sample of Dutch patients visiting a general practitioner (GP) with psychological problems (n=379). Responders completed a paper-and-pencil version of the 50-item 4DSQ and a psychometric evaluation was performed to check if the data agreed with item response theory (IRT) assumptions. Next, a CAT simulation was performed for each of the four 4DSQ scales (distress, depression, anxiety, and somatization), based on the given responses as if they had been collected through CAT. The following two stopping rules were applied for the administration of items: (1) stop if measurement precision is below a predefined level, or (2) stop if more than half of the items of the subscale are administered.
  
  
  RESULTS
  In general, the items of each of the four scales agreed with IRT assumptions. Application of the first stopping rule reduced the length of the questionnaire by 38% (from 50 to 31 items on average). When the second stopping rule was also applied, the total number of items could be reduced by 56% (from 50 to 22 items on average).
  
  
  CONCLUSIONS
  CAT seems useful for improving the efficiency of the 4DSQ by 56% without losing a considerable amount of measurement precision. The CAT version of the 4DSQ may be useful as part of an online assessment to investigate the severity of mental health problems of patients visiting a GP. This simulation study is the first step needed for the development a CAT version of the 4DSQ. A CAT version of the 4DSQ could be of high value for Dutch GPs since increasing numbers of patients with mental health problems are visiting the general practice. In further research, the results of a real-time CAT should be compared with the results of the administration of the full scale.
authors.affiliation: Netherlands Institute for Health Services Research (NIVEL), Utrecht, Netherlands.
authors.forename: Tessa
authors.identifier: http://orcid.org/0000-0002-6029-0906
authors.initials: T
authors.lastname: Magnée
authors.affiliation: Netherlands Institute for Health Services Research (NIVEL), Utrecht, Netherlands.
authors.forename: Derek P
authors.identifier: http://orcid.org/0000-0002-0166-6897
authors.initials: DP
authors.lastname: de Beurs
authors.affiliation: EMGO Institute for Health and Care Research, Department of General Practice and Elderly Care Medicine, VU University Medical Center, Amsterdam, Netherlands.
authors.forename: Berend
authors.identifier: http://orcid.org/0000-0002-8944-5238
authors.initials: B
authors.lastname: Terluin
authors.affiliation: Netherlands Institute for Health Services Research (NIVEL), Utrecht, Netherlands.|Groningen University, University Medical Center Groningen, Department of General Practice, Groningen, Netherlands.
authors.forename: Peter F
authors.identifier: http://orcid.org/0000-0001-5764-3451
authors.initials: PF
authors.lastname: Verhaak
keywords: Four-Dimensional Symptom Questionnaire; computerized adaptive testing; general practice; item response theory; mental health