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Careless responding by mental health patients on self-report assessments is rarely investigated in routine care despite the potential for serious consequences such as faulty clinical decisions. We investigated validity indices most appropriate for detecting careless responding in routine outcome monitoring (ROM) in mental health-care. First, we reviewed indices proposed in previous research for their suitability in ROM. Next, we evaluated six selected indices using data of the Brief Symptom Inventory and the Mood and Anxiety Symptom Questionnaire from 3,483 outpatients. Simulations showed that for typical ROM scales the L m a x index, Mahalanobis distance, and inter-item standard deviation may be too strongly confounded with the latent trait value to compare careless responding across patients with different symptom severity. Application of two different classification methods to the validity indices did not converge in similar prevalence estimates of careless responding. Finally, results suggest that careless responding does not have a substantial biasing effect on scale-score statistics. We recommend the l z p person-fit index to screen for random careless responding in large ROM data sets. However, additional research should further investigate methods for detecting repetitive responding in typical ROM data and assess whether there are specific circumstances in which simpler validity statistics or direct screening methods perform similarly as the l z p index.

We applied item response theory based person-fit analysis (PFA) to data of the Outcome Questionnaire-45 (OQ-45) to investigate the prevalence and causes of aberrant responding in a sample of Dutch clinical outpatients. The [Formula: see text] person-fit statistic was used to detect misfitting item-score patterns and the standardized residual statistic for identifying the source of the misfit in the item-score patterns identified as misfitting. Logistic regression analysis was used to predict person misfit from clinical diagnosis, OQ-45 total score, and Global Assessment of Functioning code. The [Formula: see text] statistic classified 12.6% of the item-score patterns as misfitting. Person misfit was positively related to the severity of psychological distress. Furthermore, patients with psychotic disorders, somatoform disorders, or substance-related disorders more likely showed misfit than the baseline group of patients with mood and anxiety disorders. The results suggest that general outcome measures such as the OQ-45 are not equally appropriate for patients with different disorders. Our study emphasizes the importance of person-misfit detection in clinical practice., (© The Author(s) 2014.)