Conference Coverage

Stroke scale cutoff might not be ideal guide for ordering CTA and detecting large vessel occlusions



In emergency department stroke consultations, the National Institute of Health Stroke Scale (NIHSS) alone does not appear to be a reliable guide for ordering diagnostic tests for a large vessel occlusion (LVO), according to large body of data presented at the 2023 annual meeting of the American Academy of Neurology.

If the goal is not to miss any LVOs, there is no NIHSS score below which these do not occur, according to Theresa Sevilis, DO, regional medical director, TeleSpecialists, Fort Myers, Fla.

For example, her evaluation of a large and nationally representative dataset shows that more than 10% of the LVOs eventually identified and accepted for intervention would be missed with a cutoff of NIHSS score of 6 or higher. Moving the cutoff NIHSS score to 4 or greater, 6% of LVOs among the 23,166 strokes evaluated would have gone undetected.

“The current guidelines do not address low NIHSS score largely due to a paucity of data,” according to Dr. Sevilis, who showed data indicating that there is great variation among institutions in regard to ordering computed tomography angiography (CTA). She indicated that CTA is the current imaging standard for detecting LVO.

Large prospective dataset

The data for this study were derived from the TeleCare database, which captures acute stroke consultations in the emergency departments in 227 facilities in 27 states. Stroke consultations over a 6-month period from July through December 2021 were evaluated. The prospectively collected data were subjected to a multivariate analysis to determine the odds ratio for a CTA performed and LVO found at each NIHSS score of 0 to 5. Scores 6 or above served as the reference.

“Only consults performed within 24 hours [of presentation] were included,” Dr. Sevilis said.

After excluding cases in which no NIHSS score was captured, which represented less than 1% of cases, more than 10,500 cases underwent CTA, providing a rate of 45.5%. The rate of CTA for the whole dataset was 45.5%. Of the study population, 24.6% had a NIHSS score of 6 or above.

“When you are discussing when to perform CTA in patients with a low NIHSS score, you are discussing the majority of patients,” Dr. Sevilis said.

Of those with a NIHSS stroke of 6 or below, 28.2% had a score of 0. Not surprisingly, these were the least likely to have a CTA performed on the basis of an odds ratio of 0.14 and the least likely to have a LVO detected (OR, 0.1). With the exception of a NIHSS stroke score of 1, the likelihood of CTA and LVO climbed incrementally with higher stroke scores. These odds ratios were, respectively, 0.16 and 0.09 for a score of 1; 0.27 and 0.16 for a score of 2; 0.33 and 0.14 for a score of 3; 0.49 and 0.24 for a score of 4; and 0.71 and 0.27 for a score of 5.

In the group with NIHSS score of 6 or above, 24.1% were found to have an LVO. Of these, the proportion accepted for a mechanical thrombectomy was less than half. The intervention acceptance rate for mechanical intervention among LVOs in patients with lower NIHSS scores again fell incrementally by score. The acceptance rate was about 35% among LVO patients with a NIHSS score of 3 or 4 and 25% for those with a score of 0-2.

The interpretation of these data “depends on goals,” Dr. Sevilis said. “If the goal is to not miss a single LVO, then it is important to consider the balance between benefits and risks.”


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