The Norwegian traumatic grief inventory-self report plus (TGI-SR+): a psychometric evaluation in traumatically bereaved people

<b>Background:</b> Prolonged grief disorder (PGD) has been added to the ICD-11 and DSM-5-TR. The Traumatic Grief Inventory-Self Report Plus (TGI-SR+) assesses self-rated PGD intensity as defined in ICD-11 and DSM-5-TR. The TGI-SR + is available in multiple languages, but has not been validated yet in Norwegian.<b>Objective:</b> The aim of this study was to evaluate the psychometric properties of the Norwegian TGI-SR + .<b>Method:</b> Bereaved adults (<i>N</i> = 307) whose child or sibling died ≥6 months ago due to a sudden or violent loss completed the TGI-SR + and measures for posttraumatic stress, depression, and precursor PGD symptoms. We examined the factor structure and internal consistency of the ICD-11 and DSM-5-TR PGD items. Convergent validity and known-groups validity was evaluated. Probable PGD cases, pair-wise agreement between diagnostic scoring rules for both PGD criteria-sets, and cut-off scores were calculated.<b>Results:</b> The 1-factor model for ICD-11 and DSM-5-TR PGD showed the best fit and demonstrated good internal consistency. Convergent validity was supported by strong associations between summed ICD-11 and DSM-5-TR PGD scores and summed posttraumatic stress, depression, and precursor prolonged grief scores. Known-groups validity was supported by PGD intensity being related to educational level and time since loss. The perfect pair-wise agreement was reached using the ICD-11 and DSM-5-TR PGD diagnostic scoring rules. The optimal cut-off score for detecting probable PGD cases, when summing all TGI-SR + items, was ≥73.<b>Conclusions:</b> The Norwegian TGI-SR + seems a valid and reliable instrument to assess ICD-11 and DSM-5-TR PGD intensity after losing a child or sibling under traumatic circumstances.