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Eosinophil Count For Early Detection Of COVID-19

Eosinophil Count For Early Detection Of COVID-19

According to new research in The Journal of the American Osteopathic Association, a rapid laboratory test, the eosinophil count, readily obtained from a routine complete blood cell count (CBC) can aid in the early recognition of COVID-19 in patients, as well as provide prognostic information.

Current testing, which relies on diagnosis of COVID-19 by nasopharyngeal swab PCR assay, remains unreliable due to variable turnaround time and a high false-negative rate.

It was found that the absence of eosinophils on the presentation can aid in early diagnosis, and in general, a persistent low count correlated with a poor prognosis for the patient. A review of the eosinophil count can be a useful tool in deciding whether to promptly isolate someone and initiate specific therapies while waiting for confirmatory test results.

What does the study say?

In the study, eosinopenia correlated with the diagnosis of COVID-19, and its persistence correlated with high disease severity and low rates of recovery. Low eosinophil count, or eosinopenia, is defined as having < 100 cells/microliter. A healthy range is typically between 100-400 cells/microliter.

Researchers compared the eosinophil results of routine CBC from the first 50 admitted COVID-19-positive patients with the eosinophil results of 50 patients with confirmed influenza infection at the time of presentation to the emergency department.


A total of 23 of the 50 patients in the COVID-19 group (46%) passed away. Eighteen out of 21 (86%) deceased patients in the COVID-19 group who initially presented with eosinopenia remained eosinophilic versus 13 out of 26 (50%) survivors who had eosinopenia on presentation.

Existing testing is challenging

The clinical diagnosis of COVID-19 is confirmed by laboratory testing with a reverse-transcription polymerase chain reaction (RT-PCR) assay, which remains a challenge due to limited test availability, variable turnaround time, and low sensitivity of RT-PCR. In many hospitals, test results may take days to return.

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