BACKGROUND: The World Health Organization (WHO) International Classification of Disease (ICD-11) is expected to include a new diagnosis for prolonged grief disorder (ICD-11PGD). This study examines the validity and clinical utility of the ICD-11PGD guideline by testing its performance in a well-characterized clinical sample and contrasting it with a very different criteria set with the same name (PGDPLOS).
METHODS: We examined data from 261 treatment-seeking participants in the National Institute of Mental Health (NIMH)-sponsored multicenter clinical trial to determine the rates of diagnosis using the ICD-11PGD guideline and compared these with diagnosis using PGDPLOS criteria.
RESULTS: The ICD-11PGD guideline identified 95.8% [95% confidence interval (CI) 93.3-98.2%] of a treatment-responsive cohort of patients with distressing and impairing grief. PGDPLOS criteria identified only 59.0% (95% CI 53.0-65.0%) and were more likely to omit those who lost someone other than a spouse, were currently married, bereaved by violent means, or not diagnosed with co-occurring depression. Those not diagnosed by PGDPLOS criteria showed the same rate of treatment response as those who were diagnosed.
CONCLUSIONS: The ICD-11PGD diagnostic guideline showed good performance characteristics in this sample, while PGDPLOS criteria did not. Limitations of the research sample used to derive PGDPLOS criteria may partly explain their poor performance in a more diverse clinical sample. Clinicians and researchers need to be aware of the important difference between these two identically named diagnostic methods.