Criterion-related validity of the diagnostic criteria for psychosomatic research for Alexithymia in patients with functional gastrointestinal disorders

Background: Because of criticism made against psychiatric assessment of somatization, alternative Diagnostic Criteria for Psychosomatic Research (DCPR) have been proposed by an international group of psychosomatic investigators. One of these criteria concerns the alexithymia construct. The main aim of the present study was to investigate the criterion-related validity of the DCPR for alexithymia syndrome (DCPR-A). A secondary aim was to explore the relationship between alexithymia and depressed mood. Method: The study included 190 consecutive outpatients with functional gastrointestinal disorders. Alexithymia was assessed by means of the DCPR-A and the 20-item Toronto Alexithymia Scale (TAS-20). Depressed mood was assessed on the basis of the Depression subscale of the Hospital Anxiety and Depression Scale (HDS) and the DSM-IV criteria. Results: The sensitivity of the DCPR-A together with the TAS-20 was 70.2%, specificity was 81.6%, positive predictive power 88.9%, negative predictive power 66.0% and overall hit rate 46.8%. DCPR-A positives scored significantly higher than DCPR-A negatives on the TAS-20 scores (t = 9.86, p < 0.001). The TAS-20 was not associated with any measure of depression, while the DCPR-A was significantly associated with the HDS and DSM-IV criteria. Conclusions: The DCPR-A had adequate sensitivity, specificity and accuracy, thus proving that the criterion has good validity. The differences in association found between alexithymia and depression suggest that they may be due to differences in the methods of investigation rather than to the constructs per se.