Document Type : Original article
Authors
1 Department of Internal Medicine, Amir Alam Hospital, Tehran University of Medical Sciences, Tehran, Iran
2 Department of Anesthesiology, Amir Alam Hospital, Tehran University of Medical Sciences, Tehran, Iran
3 Department of Ear, Nose and Throat (ENT) Diseases, Amir Alam Hospital, Tehran University of Medical Sciences, Tehran, Iran
4 Rheumatology Research Center, Tehran University of Medical Sciences, Tehran, Iran
5 Iranian Research Center for HIV/AIDS, Iranian Institute for Reduction of High-Risk Behaviors, Tehran University of Medical Sciences, Tehran, Iran
Abstract
Keywords
Background: Routine blood testing consists of Complete Blood Count (CBC) indices together with Comprehensive Metabolic Panel (CMP) which have significant roles in both diagnosis and prognosis of the novel coronavirus disease 2019 (COVID-19).
Methods: A total number of 942 COVID-19 patients and 400 healthy persons as the control group were enrolled in this study. All patients were admitted to a single center and were divided into two groups according to disease severity (severe or non-severe). Routine laboratory findings of peripheral blood sample were collected and then analyzed.
Results: Neutrophil-Lymphocyte Ratio (NLR) had the highest sensitivity and specificity value for COVID-19 diagnosis. Among patients with different severities of COVID-19, the amount of neutrophil, NLR, platelet, hemoglobin, Red cell Distribution Width (RDW) and total bilirubin was significantly different (p<0.01).
Conclusion: Some indices of complete blood count and comprehensive metabolic panel have diagnostic and prognostic roles in COVID-19 patients, which are helpful in early diagnosis, predicting severity and adverse outcomes of patients with COVID-19.
Keywords: Bilirubin, Blood cell count, Blood platelets, Coronavirus, COVID-19, Erythrocyte indices, Hematologic tests, Humans, Lymphocytes, Neutrophils
Introduction
Over 80 million people were infected by the contagious virus, COVID-19, and nearly 2 million deaths occurred all over the world (1). Person to person potential transmission modes of COVID-19 include airborne, droplet, oral and fecal transmission and contact with contaminated surfaces (2).
Many patients present with fever, chills and myalgia within first days and other symptoms may appear in the following days (3). COVID-19 is known to cause serious respiratory symptoms but it can exclusively affect other body systems like immune, neurological and hematopoietic system (4). COVID-19 causes mild to severe illness ranging from flu-like syndrome and gastroenteritis to more severe diseases such as Acute Respiratory Distress Syndrome (ARDS), metabolic acidosis and coagulopathy leading to multiple organ dysfunction and death. Disease mortality rate is about 1% and mainly due to acute respiratory failure, septic shock and failure of major organs (5,6). Previous studies suggest that diabetes mellitus, hypertension, and old age cause a significant increased risk of mortality among patients with COVID-19 (7).
There are also some potential long-lasting problems caused by COVID-19 Lung and heart injuries, vascular thrombosis, heart attack and brain stroke are the most frequent late complications (8).
The disease is confirmed by detection of SARS-CoV-2 RNA, through nasopharyngeal swab, by reverse transcription Polymerase Chain Reaction (PCR) which gives about 30% false negative results and in such cases, typical findings of chest CT scan may be helpful (6,9). As lungs are not always involved in this disease and both PCR and CT scan are expensive and not always available, clinicians may need other laboratory indices for early diagnosis of COVID-19.
On the other hand, both clinical and laboratory findings at the first visit may help the clinician to detect patients who may develop the severe form and need more intensive care. Blood cell indices and serum levels of C-Reactive Protein (CRP), Erythrocyte Sedimentation Rate (ESR), D-dimers, ferritin, cardiac troponin and IL-6 may reflect the severity of COVID-19 at the early stage (10,11).
Therefore, this study was designed to evaluate the diagnostic and prognostic value of Complete Blood Count (CBC) and metabolic indices as well as Liver Function Tests (LFT) in COVID-19 patients. In fact, an attempt was made to provide laboratory evidence for early diagnosis and treatment of patients and prediction of severe cases that required more intensive care.
Materials and Methods
Study design and participants
In this retrospective case-control study, nine hundred forty-two confirmed COVID patients (whether with PCR or typical findings of chest CT) from March 2020 to January 2021 and 400 age-sex matched healthy persons as the control group were enrolled in this study. All the patients were admitted to a single center (Amir Alam Hospital, Tehran, Iran) and divided into two groups according to the illness severity (Severe or non-severe). The detailed criteria for detecting severe patients were based on the national guidelines, with any of the following listed items: rapid progressive respiratory manifestations with a respiratory rate of ≥30 breaths per minute, the oxygen saturation (SpO2) ≤90% at rest, increase in alveolar-arterial oxygen gradient, PaO2/FiO2≤300 mmHg and >50% lung involvement (12). Routine laboratory findings of peripheral blood smear were collected from all patients and healthy group members and then analyzed.
Ethical approval for this study was obtained from the institutional ethics board of Tehran University of Medical Sciences (IR.TUMS.AMIRALAM.REC.1399.036) and participants signed informed written consent forms.
Statistical analysis
For data analysis, SPSS software v 22 (IBM, USA) was used and a p value <0.05 was considered statistically significant. Normally distributed data were analyzed by t-test and expressed as mean ± SD; non-normally distributed data were analyzed by Mann-Whitney U-test or the Wilcoxon signed-rank test and presented as medians with IQR (P25, P75). A Chi-square test was used to analyze categorical data. Qualitative data were reported as number (%).
Results
Nine hundred forty-two confirmed COVID-19 patients from March 2020 to January 2021 were enrolled in this retrospective case-control study including 602 males (64%) and 340 females (36%) with mean age of 54.7±16.3. Healthy subjects including 260 males (65%) and 140 females (35%) with mean age of 52.15±9.74 were selected as the control group. Patients were divided into two groups according to the need for intensive care (severe or non-severe). Those with severe disease included 167 patients (17.7%) with mean age of 67.1±15.5 years. In non-severe group, there were 775 patients (82.3%) with mean age of 48.6±12.74 years.
There was no significant difference in terms of sex or age among two groups (p>0.05).
In whole blood evaluation, unlike White Blood Cell (WBC), Mean Corpuscular Volume (MCV), Red cell Distribution Width (RDW), the value of Neutrophil (Neut), Lymphocyte (Lymph), Hemoglobin (Hb), platelet, Neutrophil-Lymphocyte Ratio (NLR) and Platelet-Lymph Ratio (PLR) were significantly different (p<0.05) between COVID-19 patients and healthy cases, while NLR had the highest sensitivity and specificity for COVID-19 diagnosis. Alanine Transaminase (ALT), Aspartate Transaminase (AST), ESR and CRP levels were significantly higher in patients rather than healthy control group. Urea, creatinine (Cr), bilirubin, and Alkaline Phosphatase (ALP) levels did not differ between two groups (p>0.1) (Table 1).
Among patients with different severity of COVID-19, the amount of Neut, NLR, PLT, Hb, RDW and total bilirubin was significantly different (p<0.01) (Table 2).
Table 1. The diagnostic value of blood routine test and general biochemical results in baseline laboratory findings of all included patients and healthy controls
|
|
COVID -19 group |
Healthy group |
p-value |
|
WBC (109/L) |
7.81± 1.74 |
6.80± 2.24 |
0.319 |
|
Neutrophil (109/L) |
5.26 ± 1.43 |
4.219 ±0.92 |
<0.01 |
|
Lymphocyte (109/L) |
1.69± 0.98 |
2.69 ± 1.10 |
<0.01 |
|
Neut/ Lymph |
2.5±0.52 |
1.41±0.64 |
<0.01 |
|
Hemoglobin (gr/dL) |
11.9 (10.8, 13.7) |
13.7 (12.5, 15.6) |
<0.01 |
|
MCV (fL) |
83.60 ± 5.865 |
85±5.75 |
0.222 |
|
RDW (%) |
13.29±0.91 |
13.78±1.13 |
0.178 |
|
PLT (109/L) |
211.50 ± 70.16 |
249.90± 59.12 |
<0.01 |
|
PLT/Lymphocyte |
201.44 ± 87.9 |
76.67± 68.44 |
<0.01 |
|
Urea (mg/L) |
37±12.8 |
30±10.9 |
0.189 |
|
Cr (mg/dl) |
1.16±0.5 |
1.07±0.41 |
0.117 |
|
AST (U/L) |
38.5 ± 18.9 |
19.9 ± 7.5 |
<0.01 |
|
ALT (U/L) |
40.4 ± 19.5 |
21.6 ± 10.7 |
<0.01 |
|
|
165.50± 70.6 |
173.40± 70.6 |
0.228 |
|
Bili-T (mg/dL) |
0.7± 0.4 |
0.6± 0.3 |
0.341 |
|
Bili-D (mg/dL) |
0.41 ± 0.2 |
0.36± 0.1 |
0.458 |
|
ESR (mm/hr) |
54.78±24 |
12±4 |
<0.01 |
|
CRP (mg/L) |
56.7±29.8 |
4±2 |
<0.01 |
Table 2. The prognostic value of baseline blood routine test and general biochemical results among patients with different severities of COVID-19
|
|
Non-severe |
severe |
p-value |
|
WBC (109/L) |
7.3 ± 1.3 |
8.2 ± 1.2 |
0.232 |
|
Neutrophil (109/L) |
4.433 ± 1.44 |
6.6419 ± 0.26 |
<0.01 |
|
Lymphocyte (109/L) |
1.96 ± 0.39 |
1.84± 0.64 |
0.429 |
|
Neut/ Lymph |
2.39±0.52 |
3.81±0.64 |
<0.01 |
|
Hemoglobin (gr/dL) |
12.9 ±2.1 |
11.00 ±2.3 |
<0.01 |
|
MCV (fL) |
83.70 ± 2.7 |
83.55 ± 2.5 |
0.155 |
|
RDW (%) |
13.01±0.41 |
14.19±0.54 |
<0.01 |
|
PLT (109/L) |
221.00 ±40.41 |
169.00±46.40 |
<0.001 |
|
PLT/Lymphocyte |
213 ± 169.7 |
159 ± 87.9 |
0.312 |
|
Urea (mg/L) |
36.34 ±12.57 |
40.75±15.76 |
0.100 |
|
Cr (mg/dl) |
1.14±0.55 |
1.24±0.48 |
0.386 |
|
AST (U/L) |
37.56 ± 21.03 |
39.33 ± 12.90 |
0.841 |
|
ALT (U/L) |
39.11 ± 24.54 |
41.02 ± 19.52 |
0.773 |
|
ALP (IU/L) |
169.50 ± 46.6 |
173.40 ± 65.6 |
0.127 |
|
Bili-T (mg/dL) |
1.04± 0.45 |
1.43 ± 0.56 |
<0.001 |
|
Bili-D (mg/dL) |
0.40± 0.15 |
0.42± 0.22 |
0.452 |
|
ESR (mm/hr) |
48.76 ±0.56 |
59.66 ±21.39 |
0.726 |
|
CRP (mg/L) |
43.33 (±19.79) |
54.00 (±24.74) |
0.965 |
To evaluate the diagnostic value of Lymph, Neut and NLR in patients with COVID-19, Receiver Operating Characteristic (ROC) curves were drawn. For diagnosis of the COVID-19, the area under ROC curve of Lymph, Neut and NLR was 0.97, 0.76 and 0.92, respectively. The preoperative Lymph value of 1.298×109/L was the optimal cutoff value for predicting COVID-19 (Sensitivity=90.6%, specificity =92.4%), the preoperative Neut value of 4.41×109/L was the optimal cutoff value for predicting COVID-19 (Sensitivity=63.2%, specificity=86.1%) and the preoperative NLR value of 2.009 was the optimal cutoff value for predicting COVID-19 (Sensitivity=93.4%, specificity=88.1%) (Figure 1). Univariate logistic regression analysis was used to identify COVID-19 patients. ROC curves of lymphocyte, neutrophil and NLR were used for auxiliary diagnosis of patients with COVID-19.
Discussion
This retrospective study of 942 patients with COVID-19 showed that the value of some blood sample indices like CBC, metabolic blood test and LFT were useful in diagnosis and prognosis of these patients and a cutoff value of 1.298×109/L was validated for the lymphocyte as the most sensitive and specific blood test for early diagnosis (Sensitivity = 90.6%, specificity=92.4%).
Recently, some retrospective studies have identified that patients with COVID-19 had significantly higher AST, ALT and LDH levels and these indices had very good accuracy in predicting patients with COVID-19. The differences in HCT, Hb, MCH, MCHC, MCV, Neut, RBC and D-dimer were statistically significant between COVID-19 patients and healthy group (13,14).
Increased Blood Urea Nitrogen (BUN), decreased thrombocytes and increased Interleukin 6 (IL-6) levels were all identified as risk factors for the severity of the disease. Peripheral blood lymphocyte was reduced in COVID-19 patients in comparison to non–COVID-19 patients. Low platelet count and lymphopenia are associated with severity and mortality rate of COVID-19 (15-17). CRP level was positively correlated with lung lesions at the early stage of COVID-19 and associated with COVID-19 severity (18) and the NLR measured at admission can be used to effectively predict the subsequent presence of serious clinical outcomes (19).
In this study, the value of Neut, Lymph, NLR, Hb, PLT and PLR was significantly different between COVID-19 patients and healthy group. AST, ALT, ESR and CRP levels were significantly higher in patients. MCV, RDW, urea, Cr and ALP levels showed no difference between COVID-19 patients and healthy group.
ROC curve analysis confirmed that Lymph, Neut and NLR could be used as indices for distinguishing COVID-19 patients from healthy cases. The cutoff values of Lymph and NLR were optimal for COVID-19 diagnosis. The sensitivity of Neut at the cutoff value was not high; therefore, if only Neut is used as the diagnostic index, it may lead to missed diagnosis of patients with COVID-19. More importantly, those indices can easily be obtained and should be preferentially evaluated for auxiliary diagnosis of patients with COVID-19. Laboratories can provide many biochemical indices for clinicians to assess the effect of treatment and patients’ organ function. Some laboratory findings such as elevated D-dimer, CRP and LDH levels as well as severe lymphopenia were associated with diseases severity, mortality and poor outcomes in hospitalized patients. All in all, a considerable number of comorbidities and biomarkers are associated with severity and presentations of COVID-19 disease, affecting its morbidity and mortality rates (6,20).
Our investigation showed the amount of Neut, NLR, PLT, Hb, RDW and total bilirubin was significantly different among patients with various severities of COVID-19. Unlike these indices, total WBC, Lymph, PLR, MCV, renal and liver function tests (Except for total bilirubin) could not be used to predict disease deterioration and serious clinical outcomes.
The results indicate that multiple indices of analysis of peripheral blood cells are useful for differentiating patients with COVID-19 from healthy cases; for differentiating severity and mortality of COVID-19, clinicians should consider the fact that although these indices are also useful, but the obtained values are different and they should be interpreted with caution.
Limitations
The present study has some limitations. First of all, it describes the potential value of blood cells and biochemistry for risk stratification of admitted patients, so that these results may not be applied to those who are not hospitalized. Second, it was impossible to eliminate the impact of treatments before hospital admission on the outcome. For example, liver function tests may be affected by NSAID therapy. Third, other factors which may have potential association with disease severity, like past medical history or socioeconomic status were not investigated. In addition, disease mortality may affect the performance of blood tests in risk stratification of disease severity and studies in populations with various rates of COVID-19 mortality are warranted. Finally, this cohort study was conducted in Tehran/Iran and may not be representative of other populations.
Conclusion
In conclusion, some indices of complete blood count, comprehensive metabolic panel, and LFT have diagnostic and prognostic roles in detection of COVID-19. As these tests are available and cost-effective, they may have valuable role in predicting the disease severity and early diagnosis.
Conflict of Interest
We declare that we have no conflicts of interest.
Ethical Approval
This study was approved by the institutional ethics board of Tehran University of Medical Sciences (No: IR.TUMS.AMIRALAM.REC.1399.036) and participants signed informed written consent forms.
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