Predictive value of the NIHSS for ADL outcome after ischemic hemispheric stroke: does timing of early assessment matter?

BACKGROUND AND PURPOSE

Early prediction of future functional abilities is important for stroke management. The objective of the present study was to investigate the predictive value of the 13-item National Institutes of Health Stroke Scale (NIHSS), measured within 72 h after stroke, for the outcome in terms of activities of daily living (ADL) 6 months post stroke. The second aim was to examine if the timing of NIHSS assessment during the first days post stroke affects the accuracy of predicting ADL outcome 6 months post stroke.

METHODS

Baseline characteristics including neurological deficits were measured in 188 stroke patients, using the 13-item NIHSS, within 72 h and at 5 and 9 days after a first-ever ischemic hemispheric stroke. Outcome in terms of ADL dependency was measured with the Barthel Index (BI) at 6 months post stroke. The area under the curve (AUC) from the receiver operating characteristic (ROC) was used to determine the discriminative properties of the NIHSS at days 2, 5 and 9 for outcome of the BI. In addition, at optimal cut-off odds ratio (OR), sensitivity, specificity, positive (PPV) and negative predicted values (NPV) for the different moments of NIHSS assessment post stroke were calculated.

RESULTS

One hundred and fifty-nine of the 188 patients were assessed at a mean of 2.2 (1.3), 5.4 (1.4) and 9.0 (1.8) days after stroke. Significant Spearman rank correlation coefficients were found between BI at 6 months and NIHSS scores on days 2 (r(s)=0.549, p<0.001), 5 (r(s)=0.592, p<0.001) and 9 (r(s)=0.567, p<0.001). The AUC ranged from 0.789 (95%CI, 0.715-0.864) for measurements on day 2 to 0.804 (95%CI, 0.733-0.874) and 0.808 (95%CI, 0.739-0.877) for days 5 and 9, respectively. Odds ratio's ranged from 0.143 (95%CI, 0.069-0.295) for assessment on day 2 to a maximum of 0.148 (95%CI, 0.073-0.301) for day 5. The NPV gradually increased from 0.610 (95%CI, 0.536-0.672) for assessment on day 2 to 0.679 (95%CI, 0.578-0.765) for day 9, whereas PPV declined from 0.810 (95%CI, 0.747-0.875) for assessment on day 2 to 0.767 (95%CI, 0.712-0.814) for day 9. The overall accuracy of predictions increased from 71.7% for assessment on day 2 to 73.6% for day 9.

CONCLUSIONS

When measured within 9 days, the 13-item NIHSS is highly associated with final outcome in terms of BI at 6 months post stroke. The moment of assessment beyond 2 days post stroke does not significantly affect the accuracy of prediction of ADL dependency at 6 months. The NIHSS can therefore be used at acute hospital stroke units for early rehabilitation management during the first 9 days post stroke, as the accuracy of prediction remained about 72%, irrespective of the moment of assessment.