Psychometric properties of the Lithuanian version of the NDDI-E in persons with epilepsy and suicidal ideation

Abstract

Background: Suicidality and depression are associated with worse epilepsy outcomes, but their screening in routine clinical practice remains insufficient and may improve with the validation of brief and accessible psychometric tools. We explored the psychometric properties of the Neurological Disorders Depression Inventory for Epilepsy (NDDI-E) in the Lithuanian population, which has one of the highest suicide rates globally.

Methods: We conducted a cross-sectional anonymous survey among adult outpatients visiting a tertiary epilepsy clinic in Vilnius, Lithuania. People with epilepsy (PWE) provided demographic and clinical information and completed the Geriatric depression scale (GDS), the Hospital anxiety and depression scale (HADS), the Beck depression inventory (BDI), the Neurological Disorders Depression Inventory for Epilepsy (NDDI-E) and the Generalized anxiety scale-7 (GAD-7). Suicidal ideation was defined as a non-zero score on the suicide item of the BDI and clinically relevant levels of depression - as a total BDI score of >16. Psychometric properties of the NDDI-E were evaluated by measuring its internal consistency, dimensionality, correlation with other depression scales, and by conducting receiver operating characteristic analysis for the detection of suicidal ideation and symptoms of depression.

Results: The study sample consisted of 246 PWE (average age 39.9 ± 16.3 years, 101 [41.1%] male), of them 31 (12.6%) and 41 (19.5% of those who completed the BDI) were identified with suicidal ideation or significant symptoms of depression, respectively. On average, PWE scored 10.4 ± 4.2 points on the NDDI-E. The instrument had good internal consistency (Cronbach's alpha = 0.863, n = 235), item-item and item-total correlation (>0.30). In factor analysis, its items comprised a single factor distinct from the GAD-7. The NDDI-E strongly correlated with other depression scales (r = 0.657 [GDS, n = 201], r = 0.657 [BDI, n = 201], r = 0.623 [HADS-D, n = 231], p < 0.001 for all). The NDDI-E had good diagnostic properties in discerning suicidal ideation (AUC = 0.858, 95%CI = 0.791-0.925). The isolated suicide item of the NDDI-E had acceptable properties in detecting suicidal ideation (AUC = 0.821, 95%CI = 0.724-0.918) as well.

Conclusion: The Lithuanian NDDI-E was shown to have good psychometric properties comparable to other versions of this scale. The NDDI-E is endorsed as a short and accessible instrument for estimating suicidal ideation among Lithuanian PWE.

Keywords: Anxiety; Depression; Premature mortality; Seizures; Suicidality.