Setareh Salehi Omran, MD
Mistry EA, Yeatts S, de Havenon A, Mehta T, Arora N, De Los Rios La Rosa F, Starosciak AK, Siegler III JE, Mistry AM, Yaghi S, Khatri P. Predicting 90-Day Outcome After Thrombectomy: Baseline-Adjusted 24-Hour NIHSS Is More Powerful Than NIHSS Score Change. Stroke. 2021.
Endovascular therapy (ET) is the recommended treatment for acute ischemic stroke due to a large vessel occlusion. Early neurological improvement and recovery, most commonly measured using the 24-hour National Institutes of Health Stroke Scale score (NIHSS), can occur in some patients undergoing thrombolysis or ET. Early measurements of NIHSS are associated with a favorable long-term functional outcome1-4 and are frequently used as an outcome measure in ET trials. Despite its utility, there appears to be a lack of consensus on the definition of early neurological recovery. An absolute decrease in NIHSS score of 4,5 8,6 or 107 or binary NIHSS outcomes have all been used to reflect early neurological recovery in various trials. However, a change in NIHSS from baseline and an arbitrarily chosen dichotomous outcome both have limitations. A change in NIHSS (from baseline to 24-hour) does not account for the baseline NIHSS and its accompanying deficits. While dichotomization can simplify statistical analyses, it also comes with several major drawbacks. Dichotomization of continuous variables such as NIHSS may lead to the loss of critical clinical information and a reduction in statistical power, underestimation of the degree of variation in outcomes between groups, and a concealment of non-linearity between the variable and outcome. Given the lack of a standardized approach, it is important to identify the best early NIHSS-based outcome measure to predict the 90-day functional outcome in ischemic stroke patients.
Mistry et al.8 performed a post-hoc analysis using data from a prospective, multicenter cohort (Blood Pressure after Endovascular Stroke Therapy) of adults receiving ET for anterior circulation acute ischemic strokes to compare the ability of different measurements of early neurological recovery in predicting 90-day functional outcome. The authors explored 5 different NIHSS-based definitions of early clinical outcomes: 1) 24 hour-NIHSS as a dichotomous measure; 2) change in NIHSS within 24 hours of ET (DNIHSS) as a dichotomous measure; 3) 24-hour NIHSS as a continuous measure, adjusted for baseline NIHSS; 4) DNIHSS as a continuous measure; 5) percent change from baseline (DNIHSS/baseline NIHSS x 100). The primary outcome was modified Rankin Scale score at 90 days. The strength of association was assessed using logistic regression (mRS score 0-2) and ordinal regression model while adjusting for age, admission glucose, history of hypertension, baseline NIHSS, Alberta Stroke Program Early CT Score, time to recanalization, recanalization status, and intravenous thrombolysis administration. Spearman r was used to determine the potential predictive power of each covariate for all models for 90-day mRS.
Of the 462 included patients, an absolute 24-hour NIHSS, adjusted for baseline score in multivariable modeling, had the highest predictive power for dichotomous mRS 0-2 (adjusted odds ratio [aOR] 0.79; 95% Confidence Interval [CI], 0.75-0.84) and ordinal mRS (aOR 0.84; 95%CI, 0.80-0.86) at 90 days. A dichotomous 24-hour NIHSS of £7 was the second best predictor (aOR 12.5; 95% CI, 7.14-20), with 80.1% sensitivity and 80.4% specificity. Through these analyses, the authors identified a nonlinear relationship between NIHSS and mRS, and were able to develop a prediction tool to calculate the probability of 90-day mRS score of 0-2 based on the baseline and 24-hour NIHSS values. This prediction tool, validated by the authors using the IMS-III trial data set, is available at https://redcap.vanderbilt.edu/surveys/?s=734P978D9E.
The authors’ findings are supported by prior studies, including a German Stroke Registry study that found an association between 24-hour NIHSS £8 and favorable outcome after ET for anterior circulation stroke (similar to the second best predictor of 24-hour NIHSS £ identified by Mistry et al.).9 This study takes a novel approach in measuring early neurological recovery by using a continuous NIHSS-based outcome measure rather than a dichotomous NIHSS, thereby eliminating the limitations of dichotomous outcome measures. Additionally, the authors were able to form a prediction tool that can be used to calculate the probability of 90-day mRS score of 0-2. The study has noteworthy limitations, including unknown applicability for patients outside the inclusion criteria (patients who received thrombolysis alone, stroke patients who had no acute stroke intervention, posterior circulation strokes). Additionally, the authors only included a limited number of covariates within their prediction tool, although they adjusted for most established predictors of outcome. Study results should be confirmed in analyses of prior large ET trials.
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8. Mistry EA, Yeatts S, Havenon Ad, Mehta T, Arora N, Rosa FDLRL, et al. Predicting 90-day outcome after thrombectomy. Stroke. 2021.
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