Eosinopenia and COVID-19 patients: So specific ?

To The Editor

During the COVID-19 pandemic, eosinopenia was described by Li et al. as a hallmark of this infection in patients presenting with fever [1]. For the prediction of positive SARS-CoV-2 cases (diagnosis based on RT-PCR), eosinopenia has a sensitivity of 74.7% and specificity of 68.7% with the area under the curve AUC of 0.717. The combination of eosinopenia and raised hs-CRP yielded a sensitivity of 67·9% and specificity of 78·2% (AUC = 0·730).

Up until end of March 20, Seasonal Influenza and COVID-19 were simultaneously present in Europe. These two infections share similar clinical and biological features and co-infections can exist [2]. We reviewed the laboratory results of two cohorts of SARS-CoV-2 (N = 50) and Influenza A (N = 41) patients (diagnosis confirmed by RT PCR). On admission, 69 patients (76% of both groups) had a total eosinophil count lower than 50/µl and 44 patients (48% of both groups) had an undetectable eosinophil count (see Table 1). Upon closer examination, in the COVID-19 group, there were more reported cases of complete eosinopenia. Moderately low basophils and monocytes count were also a common finding.

Table 1

Epidemiological and laboratory characteristics of the study population*.

	Whole population (n = 91, 48 M/43 F)	COVID 19 (n = 50, 31 M/19 F)	Type A Influenza (n = 41, 17 M/24 F)	p-value⁎⁎
Age (years)	63.0 ± 16.0	63.2 ± 12.8	62.9 ± 19.4	NS
Hb (g/dL)	12.3 ± 2.0	12.6 ± 1.8	11.9 ± 2.2	NS
WBC (103/µL)	8043 ± 3953	7029 ± 3852	8239 ± 4410	NS
Neutrophils (/µL)	6201 ± 3665	5712 ± 3395	6075 ± 3880	NS
Lymphocytes (/µL)	828 ± 377	894 ± 415	998± 893	NS
Monocytes (/µL)	529 ± 417	449 ± 298	716 ± 515	0,003
Eosinophils	32 ± 84	27 ± 75	49 ± 72	NS
(Eo) (/µL)	10	0	10	0.01ᶧ
Median (/µL)	44 (48%)	30 (60%)	14 (34%)
Eo Not measurable (n=,%)	69 (76%)	43 (86%)	26 (63%)
Eo < 50/µL	22 (24%)	7 (14%)	15 (37%)
(n=,%)
Eo ≥ 50/µL
(n=,%)
Basophils
(/µL)	21 ± 18	19 ± 20	31 ± 29	0,01
Platelets
(103/µL)	222 ± 110	218 ± 112	208 ± 96	NS
CRP (mg/L)	164 ± 125	133.9 ± 101.1	96 ± 118	NS

ICU= intensive care unit, M= males, F= females, SD= standard deviation, WBC= white blood cells, CRP= C-reactive protein.

Mean Value ± SD.

T-test, ᶧ chi-squared test for percentage comparison.

As such from the above, we can reach to the conclusion that complete eosinopenia is a common finding in both COVID-19 and Seasonal Influenza infections. Thus result could imply that eosinopenia could be considered as a potential biological indicator of either Influenza or SARS-COV-2 infections. This could be very useful when both diseases are prevalent at the same time. Moreover, as shown by Li et al., severe cases of eosinopenia should raise the suspicion of a COVID-19 infection, outside of the flu season.

Contribution:

YJC, CH, FA wrote the manuscript

FA and YJC: data collection

Declaration of Competing Interest

No conflict of interest for all authors