Basic demographic factors and blood biomarkers in the COVID-19 and nonCOVID-19 groups
The median age (range) was 50.56 years (25-82 years) in patients with COVID-19 and 41.87 years (17-85 years) in the controls. And there was no significant difference in the sex ratio between the two groups. As for laboratory findings, COVID-19 patients had significantly lower levels of leukocytes (5.18×109/L), lymphocytes (1.08×109/L), eosinophils (0.01×109/L) compared with the controls. When dichotomized into binary variables, eosinopenia(<0.02×109/L) and lymphocyte(<1.1×109/L) decline were present in 57.2% and 55.7% of COVID-19 patients, much higher than 35.2% and 43.7% of the controls, respectively. Meanwhile, 92.3% of the patients with COVID-19 and 84.0% of the controls had normal or decreased number of leukocytes and/or lymphopenia, two recommended parameters in the guideline.(As shown in Table 1)
Variables COVID cases (n=131) Controls (n=119) P value
|
Clinical features
Age, years-median (range) 50.56(25-82) 41.87(17-85) 0.119
Sex
Male 67(51.1) 50(42.0%)
Female 64(48.9%) 69(58%) 0.149
Blood biomarkers
Leukocyte(109/L) 5.18(3.92-6.79) 6.0(4.82-7.88)
Normal or decreased (≤9.5) 117(89.3%) 56(47.0%) 0.000*
Lymphocyte(109/L) 1.08(0.66-1.55) 1.40(1.05-1.83)
Decreased (<1·1) 73(55.7%) 52(43.7%) 0.001*
Eosinophil(109/L) 0.01(0-0.06) 0.04(0.01-0.09)
Decreased (<0·02) 75(57.2%) 42(35.2%) 0.001*
Guideline parameters
(Normal or decreased leukocyte 121(92.3%) 100(84.0%) 0.04*
and/or decreased lymphocyte)
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Note: Data are presented as n (%) and median (IQR). P values denoted the comparison between COVID cases and Controls. P <0.05 was considered statistically significant.
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Table 1
Comparison of clinical features and blood biomarkers between patients with and without COVID-19
We further evaluated the predictive capacity of those significant blood biomarkers (leukocytes, lymphocytes and eosinophils). Among the 3 biomarkers, we found that the eosinopenia produced the highest specificity (90.4%), PPV (88·3%), and AUC (0.825). We found that the combination of eosinopenia and lymphocyte decline yielded the highest specificity (91.6%), PPV (89.5%), and AUC (0.843).(As shown in Table 2 and Figure 1)
Prediction models
|
AUC
|
SE
|
95%CI
|
Sensitivity
|
Specificity
|
PPV
|
NPV
|
Leu (≤9.5)
|
0.696
|
0.034
|
0.635-0.752
|
56.5%
|
85.7%
|
81.3%
|
64.2%
|
Lym(<1.1)
|
0.794
|
0.027
|
0.739-0.843
|
68.7%
|
75.6%
|
75.6%
|
68.7%
|
Eos (<0·02)
|
0.825
|
0.026
|
0.772-0.870
|
63.4%
|
90.4%
|
88.3%
|
69.7%
|
Eos (<0·02) and Lym (<1.1)
|
0.843
|
0.024
|
0.792-0.886
|
64.9%
|
91.6%
|
89.5%
|
70.3%
|
The unit is 109/L for Leu, Lym, and Eos. AUC, area under the curve; COVID-19, coronavirus disease; Eos: eosinopenia; Lym: Lymphocyte; Leu: normal or decreased number of leukocytes; NPV, negative predictive value; PPV, positive predictive value.
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Table 2
Diagnostic performance of single and combined blood biomarkers on differentiating patients with COVID-19 (n=131) from controls patients (n=119)
Basic demographic factors and blood biomarkers in the nonsevere and severe groups
The median age (range) was 43.6 years (27-72 years) in the nonsevere patients and 68 years (36-82 years) in the severe patients with COVID-19. We found patients in the severe group are significantly older than those in the nonsevere group. And there was still no significant difference in the sex ratio between the two groups. As for laboratory findings, severe patients had significantly higher levels of leukocytes (7.4×109/L) than nonsevere group and had lower levels of lymphocytes (0.45×109/L), eosinophils (0.00×109/L) compared with the nonsevere patients. When dichotomized into binary variables, lymphocyte(<1.1×109/L) and eosinopenia(<0.02×109/L) count decline were present in 83.7% and 91.8% of severe patients, much significantly higher than 37.2% and 43.6% of the nonsevere patients, respectively. (As shown in Table 3)
Variables Nonsevere patients Severe patients P value
|
Clinical features
Age, years-median (range) 43.6(27-72) 68(36-82) 0.000*
>50 year 35(37.2%) 34(91.8%) 0.000*
Sex
Male 49(52.1%) 18(48.6%)
Female 45(47.9%) 19(51.4%) 0.720
Blood biomarkers
Leukocyte(109/L) 4.76(3.63-5.93) 7.40(5.15-10.5)
Normal or decreased (≤9.5) 90(95.7%) 27(72.9%) 0.000*
Lymphocyte(109/L) 1.30(0.92-1.67) 0.45(0.29-0.69)
Decreased (<1·1) 35(37.2%) 31(83.7%) 0.000*
Eosinophil(109/L) 0.03(0.01-0.09) 0.00(0.00-0.01)
Decreased (<0·02) 41(43.6%) 34(91.8%) 0.000*
|
Note: Data are presented as n (%) and median (IQR). P values denoted the comparison between Nonsevere and Severe patients. P <0.05 was considered statistically significant.
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Table 3
Comparison of clinical features and blood biomarkers between nonsevere and severe patients with COVID-19
We further evaluated the predictive capacity of eosinophils differentiating nonsevere and severe patients with COVID-19. We found that the result of specificity (86.2%), PPV (63.9%) and AUC (0.750). (As shown in Table 4 and Figure 2)
Prediction models
|
AUC
|
SE
|
95%CI
|
Sensitivity
|
Specificity
|
PPV
|
NPV
|
EOS (<0·02)
|
0.750
|
0.049
|
0.667-0.822
|
62.2%
|
86.2%
|
63.9%
|
85.3%
|
The unit is 109/L for Eos. AUC, area under the curve; COVID-19, coronavirus disease; Eos: eosinopenia; NPV, negative predictive value; PPV, positive predictive value
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Table 4
Diagnostic performance of Eosinophil on differentiating nonsevere and severe patients with COVID-19
Blood biomarkers dynamic changes of patients with COVID-19
We randomly selected 20 survivors and 20 nonsurvivors from the patients with COVID-19, and analyzed their dynamic changes in blood biomarkers over time. As shown in Figure 3A, although the white blood cell count of the survivors increased temporarily in the early stage, it gradually decreased to the normal level later. The level of white blood cell count of the nonsurvivors increased in the early stage, although it decreased afterwards, but eventually gradually increased to a higher level. In Figure 3B, we found that the lymphocyte count of survivors showed a gradual upward trend with time. In the figure we found that around the 17th day, the cell count rose to normal levels. However, the lymphocyte count of the nonsurvivors has been at a low level, and the increase is not obvious. From Figure 3C, we can see that the eosinophil count of the survivors rose quickly, rose to normal levels around the fifth day, and then continued to increase. However, the eosinophil count of the nonsurvivors continues to be low, below normal levels.
Relationship between blood biomarkers and recovery of patients with COVID-19
In the cured group, there were 75 patients with eosinophil count and 73 patients with lymphocyte count below the lower limit of normal before treatment. In these patients, the average time for eosinophil count to return to normal was 6.2(4.6-7.8) days, the average time for lymphocytes to return to normal levels was 18.5(16.7-20.6) days, and the average time for nucleic acid to turn negative was 17.2(15.5-19.0) days. Data are presented as median (IQR).
In order to study the relationship between blood biomarkers and recovery of COVID-19 patients, we selected two surviving cases. As shown in Figures 4A and B, these are the results of chest CT imaging taken at different times after the patient was admitted to our hospital. Case 1 is a 34-year-old young man and case 2 is a 57-year-old middle-aged male. Figures 4 C and D are the dynamic changes of blood biomarkers in case1 and case2, respectively.
In case 1, the patient was transferred from the external hospital and the chest CT was examined in the external hospital, so there was no imaging examination on the first day of admission. We found that on the 14th day, from the lung CT, the patient's lungs were still very heavy, but the white blood cells had dropped to normal, eosinophils had risen to normal, but the lymphocytes were still below normal. On the 25th and 27th day of admission, the patient's pharyngeal swab was negative for nucleic acid inspection, but the patient's lung CT showed a slight exudative lesion. At this time, the lymphocytes did not increase to the normal range. The lymphocyte count did not reach normal levels until the lung CT showed that the exudative lesions were significantly improved.
In case 2, the patient's lung CT showed exudative lesions after admission, and the lung infection continued to increase until day 26. But through active treatment, the patient's lymphocyte and eosinophil counts continue to rise, and eosinophils have risen to normal levels on about day 7.On day 35 and 37, the patient's throat swab nucleic acid test showed negative results. At this time, the patient's white blood cells have dropped from the previous high level, and the lymphocyte count has gradually increased to normal.
Relationship between recovery of eosinophil count and patient prognosis
Finally, according to the recovery of eosinophils, we divided these patients with COVID-19 into two groups. One group (n=14) is a group with eosinophils continuously lower than normal level, and the other group (n=13) is a group with eosinophils level elevated to normal. We counted the one-month survival of these two group patients and made survival curves, as shown in Figure 5. We found that patients whose eosinophils level has not recovered have significantly shorter survival times than those who recovered.