Background: The National Institutes of Health Stroke Scale (NIHSS) is a well-known and validated scale to measure the severity of symptoms associated with stroke. NIHSS item 9, “Best Language”, is often used to ascertain initial aphasia, however, data on how well NIHSS item 9 can discriminate aphasia in stroke patients is incomplete. We investigated if NIHSS item 9 is a reliable tool to diagnose patients with aphasia in the acute phase of first-ever ischemic stroke.
Methods: 56 patients with first-ever acute ischemic stroke were included prospectively and consecutively in the Lund Stroke Register Study. Patients were excluded if they had any of the following characteristics: 1) diagnosed dementia or psychiatric disorders; 2) non-native Swedish language; 3) altered consciousness. Patients were assessed within 7 days after stroke onset by a trained research nurse with the NIHSS item 9 followed by a language evaluation with the Language Screening Test (LAST, range 0-15, where 0-14 indicate aphasia) within 24 hours of the NIHSS item 9 assessment, by a licensed speech and language pathologist. Data were analyzed using LAST as a ‘gold standard.’
Results: Of 56 first-ever ischemic stroke patients (median age 79 years; n=37 female, n= 19 male) 9 patients (16%) had aphasia according to NIHSS item 9 (the distribution of scores 1-3 were n=6, n=1, and n=2, respectively). When using LAST 17 patients (30%) had aphasia (score ≤14) with a median LAST score of 13 (IQR 10-14). The median LAST score for patients with NIHSS item 9 with a score of 0, but LAST ≤ 14 (n= 10) was 14 (IQR 13-14). Assuming LAST as gold standard, NIHSS item 9 gave 10 false negatives for aphasia (LAST scores ranging from 12 to 14) and 2 false positives (both with NIHSS item 9 score of 1) for aphasia, translating into a sensitivity of 34% and a specificity of 95%.
Conclusions: Our results indicate that the sensitivity of NIHSS item 9 is low compared to more in depth testing by a speech and language pathologist. Using NIHSS item 9 as a diagnostic tool for aphasia after stroke can misclassify patients with mild to moderate aphasia.