Monitoring psychotherapeutic progress requires valid and economic measures to detect change of clinical relevance. We addressed validity and sensitivity to change of the 'Klinisch Psychologisches Diagnosesystem 38' (KPD-38, Clinical Psychological Diagnosis System), an instrument for outcome monitoring and quality assurance.
Data from an inpatient sample (n = 1.377) were used to investigate the concurrent validity, the sensitivity to change, and the criterion validity of the KPD-38 in comparison to the Outcome Questionnaire (OQ-45) and the Brief Symptom Inventory (BSI).
Sensitivity-specificity analyses showed similar sensitivity and higher specificity for the KPD-38 scales compared with the BSI and OQ total scores. Change rates on the KPD-38 distress scale (DIS) were found to be lower than on the BSI (KPD-38 DIS: 36.6%, GSI: 67.7%) and the OQ-45 (KPD-38 DIS: 44.3%, OQ tot: 57.1%) total scores. Concordance was low with the BSI ([κ = 0.24] and moderate with the OQ-45 [κ = 0.45]).
Implications for applications in the field of outcome assessment and the challenge of further validation are discussed. The relation between sensitivity to change and criterion validity is highlighted.