Is my patient suffering clinically significant emotional distress? Demonstration of a probabilities approach to evaluating algorithms for screening for distress.

GOALS OF WORK: Screening oncology patients for clinically significant emotional distress is a recommended standard of care in psycho-oncology. However, principles regarding the interpretation of screening and diagnostic tests developed in other areas of medicine have not been widely applied in psycho-oncology. This paper explores the application of the concepts of likelihood ratios and post-test probabilities to the interpretation of psychological screening instruments and demonstrates the development of an algorithm for screening for emotional distress and common psychopathology.
MATERIALS AND METHODS: Three hundred forty oncology/haematology outpatients at the Calvary Mater Newcastle, Australia completed the Distress Thermometer (DT), the PSYCH-6 subscale of the Somatic and Psychological Health Report and the Kessler-10 scale. The Hospital Anxiety and Depression Scale (HADS) (cutoff 15+) was used as the gold standard. MAIN
RESULTS: Likelihood ratios showed that a score over threshold on the DT was 2.77 times more likely in patients who were cases on the HADS. These patients had a 53% post-test probability of being cases on the HADS compared with the pretest probability of 29%. Adding either the PSYCH-6 (3+) or the Kessler-10 (22+) to the DT (4+) significantly increased this post-test probability to 94% and 92%, respectively. The significance of these improvements was confirmed by logistic regression analysis.
CONCLUSIONS: This study demonstrated the application of probability statistics to develop an algorithm for screening for distress in oncology patients. In our sample, a two-stage screening algorithm improved appreciably on the performance of the DT alone to identify distressed patients. Sequential administration of a very brief instrument followed by selective use of a longer inventory may save time and increase acceptability.