Challenges of Estimating Accurate Prevalence of Arm Weakness Early After Stroke.
Lisa A Simpson, Kathryn S Hayward, Moira McPeake and 2 others
PMID 34319189WHAT IT FOUND
Estimates of arm weakness after stroke vary widely depending on how and when you measure it.
A SAFE score at two days found 40% weakness, while an NIHSS score at admission found 59%. The 70% figure often cited is outdated and method-dependent.
Key findings
01Using the SAFE score at a mean of 1.9 days post-stroke, 39.9% of patients had upper limb weakness, compared to 56.6% using the initial NIHSS arm score at admission.
02There was significant disagreement between measures: 22.3% of patients were classified as having little to no weakness by the SAFE score despite showing weakness on the initial NIHSS arm score.
03The severity profile of weakness was bimodal, with 60.1% having little to no weakness and 16.1% having a flaccid arm (SAFE score of 0).
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTsWhat it means for SLPs
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What it does not show
The study was conducted at a single comprehensive stroke centre, so results may not generalize to other settings. The SAFE score threshold for weakness (<=8) excluded individuals with scores of 9, who may still have mild weakness, potentially underestimating true prevalence. Data collection for the SAFE score was retrospective screening data, and some patients were excluded because they were too unwell, discharged early, or had severe aphasia, which may bias the sample away from the most severe cases. The NIHSS arm score only measures antigravity movement without resistance, so it may not capture the full spectrum of weakness compared to multicomponent measures.
Declared interests
The authors declared no potential conflicts of interest. Funding was provided by the Canadian Institutes of Health Research, the Canada Research Chairs Program, the National Health and Medical Research Council of Australia, the Michael Smith Foundation for Health Research, and the Heart and Stroke Foundation of Canada.
The easy way to misread this
Do not interpret the lower prevalence of weakness (40%) found in this study as evidence that stroke is causing less arm weakness today. This figure depends entirely on using the SAFE score at two days post-stroke; using the NIHSS at admission in the same patients yielded 56.6%. The 'true' prevalence is elusive and method-dependent.