COVID-19 Diagnosed on CTA Scan in Stroke Patients

October 29, 2020

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A routine scan used to evaluate some acute stroke patients can also detect SARS-CoV-2 infection in the upper lungs, a new study shows.

Dr Charles Esenwa

"As part of the stroke evaluation work-up process, we were able to diagnose COVID-19 at the same time at no extra cost or additional workload," lead author Charles Esenwa, MD, commented to Medscape Medical News. "This is an objective way to screen for COVID-19 in the acute stroke setting," he added.

Esenwa is an assistant professor and a stroke neurologist at the Montefiore Medical Center/Albert Einstein College of Medicine in New York City.

He explained that during the COVID-19 surge earlier this year, assessment of patients with severe acute stroke using computed tomography angiogram (CTA) scans ― used to evaluate suitability for endovascular stroke therapy ― also showed findings in the upper lung consistent with viral infection in some patients.

"We then assumed that these patients had COVID-19 and took extra precautions to keep them isolated and to protect staff involved in their care. It also allowed us to triage these patients more quickly than waiting for the COVID-19 swab test and arrange the most appropriate care for them," Esenwa said.

The researchers have now gone back and analyzed their data on acute stroke patients who underwent CTA at their institution during the COVID-19 surge. They found that the changes identified in the lungs were highly specific for diagnosing SARS-CoV-2 infection.

The study was published online on October 29 in Stroke.

"Stroke patients are normally screened for COVID-19 on hospitalization, but the swab test result can take several hours or longer to come back, and it is very useful for us to know if a patient could be infected," Esenwa noted.

"When we do a CTA, we look at the blood vessels supplying the brain, but the scan also covers the top of the lung, as it starts at the aortic arch. We don't normally look closely at that area, but we started to notice signs of active lung infection which could have been COVID-19," he said. "For this paper, we went back to assess how accurate this approach actually was vs the COVID-19 PCR test."

The researchers report on 57 patients who presented to three Montefiore Health System hospitals in the Bronx, in New York City, with acute ischemic stroke and who underwent CTA of the head and neck in March and April 2020, the peak of the COVID-19 outbreak. The patients also underwent PCR testing for COVID-19.

Results showed that 30 patients had a positive COVID-19 test result and that 27 had a negative result. Lung findings highly or very highly suspicious for COVID-19 pneumonia were identified during the CTA scan in 20 (67%) of the COVID-19–positive patients and in two (7%) of the COVID-19–negative patients.

These findings, when used in isolation, yielded a sensitivity of 0.67 and a specificity of 0.93. They had a positive predictive value of 0.19, a negative predictive value of 0.99, and accuracy of 0.92 for the diagnosis of COVID-19.

When apical lung assessment was combined with self-reported clinical symptoms of cough or dyspnea, sensitivity for the diagnosis of COVID-19 for patients presenting to the hospital for acute ischemic stroke increased to 0.83.

"We wondered whether looking at the whole lung would have found better results, but other studies which have done this actually found similar numbers to ours, so we think actually just looking at the top of the lungs, which can be seen in a stroke CTA, may be sufficient," Esenwa said.

He emphasized the importance of establishing whether an acute stroke patient has COVID-19. "If we had a high suspicion of COVID-19 infection, we would take more precautions during any procedures, such as thrombectomy, and make sure to keep the patient isolated afterwards. It doesn't necessarily affect the treatment given for stroke, but it affects the safety of the patients and everyone caring for them," he commented.

Esenwa explained that intubation ― which is sometime necessary during thrombectomy ― can expose everyone in the room to aerosolized droplets. "So we would take much higher safety precautions if we thought the patient was COVID-19 positive," he said.

"Early COVID-19 diagnosis also means patients can be given supportive treatment more quickly, admitted to ICU if appropriate, and we can all keep a close eye on pulmonary issues. So having that information is important in many ways," he added.

Esenwa advises that any medical center that evaluates acute stroke patents for thrombectomy and is experiencing a COVID-19 surge can use this technique as a screening method for COVID-19.

He pointed out that that the Montefiore Health System had a very high rate of COVID-19. That part of New York City was one of the worst hit areas of the world, and the CTA approach for identifying COVID-19 has only been validated in areas with such a high local incidence of COVID. If used in an area of lower prevalence, the accuracy would likely be less.

"We don't know if this approach would work as well at times of low COVID-19 infection where any lung findings would be more likely to be caused by other conditions, such as pneumonia due to other causes or congestive heart failure. So there would be more false positives," Esenwa said.

"But when COVID-19 prevalence is high, the lung findings are much more likely to be a sign of COVID-19 infection. As COVID-19 numbers are now rising for a second time, it is likely to become a useful strategy again."

The study was approved by the Albert Einstein College of Medicine/Montefiore Medical Center Institutional Review Board and had no external funding. Esenwa has disclosed no relevant financial relationships.

Stroke. Published online October 29, 2020. Full text

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