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(Stroke. 2006;37:920.)
© 2006 American Heart Association, Inc.
Research Reports |
From the Department of Neurology (A.B., L.S.W.), Roudebush VA Medical Center (L.S.W.), and Section of Biostatistics (C.S.), Department of Medicine, Indiana University School of Medicine, Indianapolis.
Correspondence to Askiel Bruno, MD, Department of Neurology, Indiana University School of Medicine, 1050 Wishard Blvd, Room R-6105, Indianapolis, IN 46202. E-mail abruno{at}iupui.edu
| Abstract |
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Methods We analyzed data from the acute stroke treatment trial Trial of Org 10172 in Acute Stroke Treatment (TOAST). Using logistic regression analysis, we modeled the probability of the TOAST predefined very favorable outcome (VFO; both Glasgow Outcome Scale 1 and modified Barthel Index 19 to 20) at 3 months. Within-subject changes (baseline3 months) on the National Institutes of Health Stroke Scale (NIHSS) was the main predictor of interest.
Results The baseline median NIHSS for the entire TOAST cohort was 7, and it improved by 4 points (interquartile range 3 to 6) among 603 patient with VFO and by 2 points (interquartile range 1 to 5) among 638 patients without a VFO (P<0.001). The odds for VFO increased by 2.29 (95% CI, 2.06 to 2.54; P<0.001) for each 1-point improvement on the NIHSS. In receiver operating characteristic analysis, final NIHSS
2 was a good predictor of VFO, but no single NIHSS change cut point was a good predictor of VFO.
Conclusions NIHSS change appears to be a useful outcome measure for acute stroke trials and is not fully comparable to dichotomized functional outcomes.
Key Words: outcome recovery of function stroke, acute
| Introduction |
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| Patients and Methods |
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Logistic regression analysis modeled for VFO. Our primary objective was to assess the effect of within-subject NIHSS change after adjusting for significant covariates. Wilcoxon rank sum test compared NIHSS change between subjects with and without VFO. Subjects who died were assigned the highest possible NIHSS score. We also compared the NIHSS change by treatment group in the TOAST subgroups showing a significant treatment effect in the TOAST trial (Table). Receiver operating characteristic (ROC) analysis assessed sensitivities and specificities of the NIHSS change and the final 3-month NIHSS in predicting VFO.
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| Results |
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Despite good correlation between NIHSS change and VFO in logistic regression analysis, ROC analysis did not find a specific cut point for NIHSS change with sufficiently high sensitivity and specificity to reliably predict VFO (area under curve 0.65; 95% CI, 0.62 to 0.68). However, analysis of the NIHSS score at 3 months as a predictor of VFO showed that a score of
2 is a good predictor of VFO (area under curve 0.91; 95% CI, 0.90 to 0.93; sensitivity 82.8%; specificity 84.6%).
| Discussion |
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As to reliably predicting the dichotomized VFO, no single NIHSS change cut point has sufficient sensitivity and specificity. This is because greater NIHSS changes are needed to achieve VFO in severe than in mild strokes. This is indicated by ROC analysis showing that a final 3-month NIHSS score dichotomized at
2 is a good predictor of VFO. Thus, to best predict VFO, a patient with a baseline NIHSS of 10 needs to improve by
8 points and a patient with a baseline of 5 by
3 points.
NIHSS change did not detect the treatment effects seen in secondary analyses in the TOAST trial (Table). At least 2 explanations for this are possible. One, NIHSS change might be a less sensitive outcome measure than the VFO. Alternatively, improvements in subjects with severe strokes who did not reach the VFO may have been such that they countered the result seen in TOAST when tested according to NIHSS change. Several acute stroke treatment trials report NIHSS change as a secondary outcome, largely in agreement with dichotomized functional outcomes.1015 NIHSS change appears to be a useful outcome measure in acute stroke trials and should be studied further.
Received November 28, 2005; revision received December 16, 2005; accepted December 20, 2005.
| References |
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