Background: Depressive symptoms among patients with amyotrophic lateral sclerosis (ALS) are usually measured with conventional questionnaires. These measurements do not consider the specific circumstances of the underlying disease. The purpose of this study was to assess the validity of a new short 12 items ALS-Depression-Inventory (ADI-12). We determined convergent, criterion, and concurrent validity. The Structured Clinical Interview (SCID) for DSM-IV was used as the gold standard and the Beck Depression Inventory (BDI) and the WHO Well Being Index (WHO-5) to assess concurrent validity.
Methods: A total of 39 ALS patients in all stages of the disease were interviewed. Convergent validity was estimated by the inter-correlation between the ADI-12 and the BDI. Criterion and concurrent validity were specified with respect to sensitivity, specificity and predictive values. Receiver Operating Characteristics (ROC) and Areas Under the Curves (AUC) were calculated.
Results: All three depression scales showed excellent internal consistencies (Cronbach's alpha: .8-.9). The correlation between the ADI-12 and the BDI was high (r=.80). For the ADI-12 a cut-off of > or = 30 (SE=100%, SP=83%) identified all patients with a current episode of major depression. A more liberal cut-off (> or = 23) identified all patients with any depressive disorder including minor depression at the cost of specificity (60%).
Conclusions: With the ADI-12 ALS patients with depressive disorders can be reliably identified. We recommend the ADI-12 for routine screening in primary care of ALS patients.