Abstract
Objective: We aimed to analyze the clinical diagnostic value of nucleic acid detection and specific IgM and IgG antibodies in COVID-19 patients. According to the patients’ test outcomes of nucleic acid and specific IgM and IgG antibodies, the patients were grouped. Methods: Medical records of 788 COVID-19 patients were collected for retrospective analysis, including demographic data, clinical characteristics, CT outcome and laboratory indicators. According to the patients’ nucleic acid detection and the results of specific IgM and IgG antibodies, the patients were grouped, and the clinical application value of COVID-19 nucleic acid detection and specific IgM and IgG antibodies was analyzed. Results: The main clinical manifestations of COVID-19 patients included in this study were fever (431 cases, 54.7%), cough (404 cases, 51.3%), and fatigue (232 cases, 29.4%), and the main comorbidities were hypertension (201 Cases, 25.4%), diabetes (86 cases, 10.9%), coronary heart disease (39 cases, 4.9%), etc. CT abnormalities mainly manifested as ground glass shadows (731 cases, 92.8%), mesh nodules shadows (413 cases, 52.4%), pulmonary fibrosis (118 cases, 15.0%), etc. The majority of patients were positive for IgM and IgG antibodies. There were 50 patients in the qPCR+IgM-IgG- group (only nucleic acid test result was positive), of which 6 patients (12%) were mild in symptoms, and 39 patients (78%) had mild CT findings. There were 321 patients in the qPCR+IgM+IgG+ group (nucleic acid and specific IgM and IgG antibody test results were positive), of which 49 patients (15.5%) were severe or critically ill, and 78 patients (24.8%) had severe CT findings. There were 291 patients in the qPCR-IgM+IgG+ group (specific IgM and IgG antibody test results were positive), of which 22 (7.5%) were severe or critically ill, and 94 (32.3%) patients had severe CT findings. The sensitivity of antibody detection for COVID-19 was higher than that of qPCR (84.9%, 86.4% vs. 53.9%, P<0.001). There were significant differences between IgM+ patients and IgM- patients in terms of age distribution, gender, sore throat, clinical classification, and CT findings (P<0.05). Conclusion: IgM antibody has a high clinical detection rate, which effectively avoids the missed detection of qPCR and increases the detection rate of COVID-19 patients. There are more severe and critically ill patients with IgM tested positive, which finding has certain guiding significance for clinical diagnosis and treatment.
Keywords: COVID-19, qPCR, IgM, IgG, clinical value
Introduction
According to the latest epidemic data, the number of confirmed cases of new coronavirus pneumonia (COVID-19) worldwide has reached 2,865,938, and the number of deaths has risen to 200,698. COVID-19, a severe acute respiratory syndrome, has many ways of transmission, with rapid speed and wide range [1]. 2019-nCoV (also known as SARS-COV-2) virus is the pathogen, whose key component, the spike protein, causes great harm to human health [2,3]. Timely control of the spread of 2019-nCoV and accurate detection methods are essential, which are of great significance for patient isolation or treatment as well as epidemic prevention and control [4]. At present, the diagnosis methods of COVID-19 include nucleic acid testing (qPCR) and antibody testing (IgM, IgG antibodies). qPCR is the gold standard for the diagnosis of COVID-19. It is a method that uses fluorescent chemicals to measure the total amount of products after each polymerase chain reaction (PCR) cycle in a DNA amplification reaction. However, it has limitations such as slow aging, complex technology, and high risk of sampling contamination. As serological testing indicators, IgM and IgG antibodies have the advantages of non-invasiveness and simple operation, and can provide auxiliary diagnostic value for the identification of COVID-19 [5,6]. Studies have shown that the seropositivity rate of IgM and IgG antibodies is high, while the sensitivity of qPCR detection is low. Antibody detection can be used as an important supplement to qPCR detection [7]. According to reports, as the IgM antibodies appear shortly in early stage, the positive IgM antibodies can indicate early infection, which can contribute to the timely detection and treatment of COVID-19. IgG antibody is produced in the second immune response, later than IgM, and can exist for a long time in the body. The positive IgG indicates that the COVID-19 patient is in the recovery period or belongs to a previous infection [6,8,9]. In addition, the combined detection of qPCR-IgM and qPCR-IgM-IgG has been reported to be of great value for improving the positive detection rate, early diagnosis and treatment of COVID-19 patients [10,11]. The above studies all reflect the importance of antibody testing to fight against the COVID-19 epidemic on the basis of nucleic acid testing. At present, research about the clinical value of COVID-19 diagnostic indicators is rare.
In this study, we analyzed the clinical data related to the diagnosis indicators (qPCR, IgM, IgG) of COVID-19 patients, hoping to provide reference value for the clinical application of the disease, and provide good suggestions for further strengthening the prevention and control of the epidemic.
Materials and methods
Patients
The medical records of 788 COVID-19 patients in our hospital from February 2020 to March 2020 were collected for retrospective analysis, including demographic data, clinical features, CT outcomes and laboratory indicators.
Inclusion criteria: Patients with complete general information; with epidemiological history; patients with positive nucleic acid test or specific IgM and IgG antibody test [12].
Exclusion criteria: Suspected patients and patients with incomplete qPCR or antibody testing.
This study strictly followed the principles of the Declaration of Helsinki and was approved by the ethics committee of our hospital.
Determination of clinical classification
According to the diagnosis and treatment plan for COVID-19, patients with mild clinical symptoms and no pneumonia on imaging were regarded as mild. Patients with symptoms of pneumonia (fever, respiratory symptoms, etc.) and imaging findings were regarded as ordinary. Adults with shortness of breath (respiratory rate ≥30 beats/min), or the oxygen saturation ≤93% in the resting state or the arterial blood oxygen partial pressure/inspired oxygen concentration ≤300 mmHg, were considered as severe. Children 9 years or older with shortness of breath (respiratory rate ≥30 beats/min, except for crying, etc.) or oxygen saturation ≤92% in resting state or groaning, nasal flapping, tri-concave sign, cyanosis, intermittent apnea, drowsiness, convulsions, refusal to eat, or dehydration, were considered as severe. Patients with respiratory failure and requiring mechanical ventilation or shock or other organ failure and requiring ICU treatment were regarded as critical.
Detection methods
2019-nCoV assay kit (fluorescence PCR method, Zhijiang Biotechnology Co., Ltd., Shanghai, China) was used to detect nucleic acid qPCR. 2019-nCoV antibody detection kit (colloidal gold method, Innotek Biotechnology Co., Ltd., Qian’an, China) was adopted for IgM and IgG antibody detection.
Statistical analysis
SPSS 25.0 was used for statistical analysis of the data. Continuous variables were expressed as median and interquartile range, and count data were expressed as n (%). The chi-square test of the R*C table was used for the enumeration data, some outcomes generated from the Fisher’s exact probability method, and Kruskal-Wallis H test results of multiple independent samples were adopted for one-way ordered data. When P<0.05, the difference was statistically significant.
Results
Analysis of clinical characteristics of COVID-19 patients
In this study, 788 COVID-19 patients with a median age of 59.5 years were included. They were mainly females (477 cases, 60.5%). The main symptoms of the patients were fever (431 cases, 54.7%), cough (404 cases, 51.3%), fatigue (232 cases, 29.4%), etc.; mainly accompanied by hypertension (201 cases, 25.4%), diabetes (86 cases, 10.9%), coronary heart disease (39 cases, 4.9%); the clinical classification was classified as common type (656 cases, 83.2%) and severe type (84 cases, 10.7%). Chest CT abnormalities were mainly ground glass shadows (731 cases, 92.8%), reticular nodules shadows (413 cases, 52.4%), and pulmonary fibrosis (118 cases, 15.0%). See Table 1.
Table 1.
Clinical features of the patients with COVID-19
| Characteristics | Patients (n=788) |
|---|---|
| Age | |
| Median (range) | 59.5 yr (9-100 yr) |
| Distribution (n, %) | |
| ≤17 yr | 5 (0.6) |
| 18-44 yr | 149 (18.9) |
| 45-64 yr | 338 (42.9) |
| 65-74 yr | 211 (26.8) |
| ≥75 yr | 85 (10.8) |
| Sex (n, %) | |
| Male | 311 (39.5) |
| Female | 477 (60.5) |
| Contact information (n, %) | |
| Unidentified source of infection | 673 (85.4) |
| Contact with suspected case | 12 (1.5) |
| Contact with confirmed case | 103 (13.1) |
| Signs and symptoms (n, %) | |
| Fever | 431 (54.7) |
| Cough | 404 (51.3) |
| Fatigue | 232 (29.4) |
| Expectaration | 49 (6.2) |
| Asymptomatic | 44 (5.6) |
| Sore throat | 13 (1.6) |
| Shortness of breath | 38 (4.8) |
| Myalgia | 11 (1.4) |
| Chest distress or pectoralgia | 84 (10.7) |
| Headache | 9 (1.1) |
| Dyspnea | 7 (0.9) |
| Nausea and vomiting | 3 (0.4) |
| Diarrhea | 5 (0.6) |
| Rhinorrhea | 3 (0.4) |
| Tachycardia | 3 (0.4) |
| Coexisting disorder (n, %) | |
| Hypertension | 201 (25.4) |
| Diabetes | 86 (10.9) |
| Coronary heart disease | 39 (4.9) |
| Cancer | 20 (2.5) |
| Cerebrovascular disease | 17 (2.2) |
| Chronic bronchitis | 11 (1.4) |
| Hepatitis B infection | 8 (1.0) |
| Asthma | 6 (0.8) |
| Chronic obstructive pulmonary disease | 4 (0.5) |
| Congestive heart failure | 3 (0.4) |
| Chronic renal disease | 3 (0.4) |
| Cirrhosis | 2 (0.3) |
| Clinical classification (n, %) | |
| Mild | 35 (4.4) |
| Moderate | 656 (83.2) |
| Severe | 84 (10.7) |
| Critical | 13 (1.6) |
| Highest axilla-temperature during hospitalization (n, %) (normal range <37.3°C) | |
| Normal | 575 (73.0) |
| Low-grade fever | 187 (23.7) |
| Moderate fever | 18 (2.3) |
| High-grade fever | 2 (0.3) |
| Leucocytes (×109/L; normal range 3.5-9.5) (n, %) | |
| Decrease | 27 (3.4) |
| Normal | 716 (90.9) |
| Increase | 25 (3.2) |
| Neutrophils (×109/L; normal range 1.8-6.3) (n, %) | |
| Decrease | 22 (2.8) |
| Normal | 709 (90.0) |
| Increase | 37 (4.7) |
| Lymphocytes (×109/L; normal range 1.1-3.2) (n, %) | |
| Decrease | 119 (15.1) |
| Normal | 640 (81.2) |
| Increase | 9 (1.1) |
| Monocyte (×109/L; normal range 0.1-0.6) (n, %) | |
| No increase | 716 (90.9) |
| Increase | 52 (6.6) |
| Platelets (×109/L; normal range 125.0-350.0) (n, %) | |
| Decrease | 32 (4.1) |
| Normal | 705 (89.5) |
| Increase | 31 (3.9) |
| Alanine aminotransferase (U/L; normal range 0-55) (n, %) | |
| No increase | 662 (84.0) |
| Increase | 72 (9.1) |
| Aspartate aminotransferase (U/L; normal range 5-34) (n, %) | |
| No increase | 677 (85.9) |
| Increase | 57 (7.2) |
| Erythrocyte sedimentation rate (mm/H; normal range 0-15) (n, %) | |
| No increase | 95 (12.1) |
| Increase | 182 (23.1) |
| Interleukin-6 (pg/mL; normal range 0-10) (n, %) | |
| No increase | 323 (41.0) |
| Increase | 25 (3.2) |
| C-reactive protein (mg/mL; normal range 0-10) (n, %) | |
| No increase | 669 (84.9) |
| Increase | 73 (9.3) |
| Procalcitonin (ng/mL; normal range 0.0-0.05) (n, %) | |
| No increase | 371 (47.1) |
| Increase | 121 (15.4) |
| D-dimer (µg/L; normal range 0.0-1.5) Increased (n, %) | |
| No increase | 451 (57.2) |
| Increase | 43 (5.5) |
| Abnormalities on chest CT-(n, %) | |
| Ground glass shadow | 731 (92.8) |
| Reticulated nodule shadow | 413 (52.4) |
| Pulmonary Fibrosis | 118 (15.0) |
| Consolidation | 49 (6.2) |
| Adjacent pleura thickening | 16 (2.0) |
| Pleural effusion | 6 (0.8) |
| Thickening around the bronchus | 9 (1.1) |
| Normal | 35 (4.4) |
| Lesion area (n, %) | |
| Normal | 35 (4.4) |
| A few lesions | 346 (43.9) |
| Some lesions | 188 (23.9) |
| Many lesions | 151 (19.2) |
| Diffuse lesions | 61 (7.7) |
Note: yr: year; COVID-19: novel coronavirus pneumonia.
Outcomes and characteristics of nucleic acid and specific IgM and IgG antibodies in COVID-19 patients
The patients were divided into seven groups: qPCR+IgM-IgG- (n=50), qPCR+IgM+IgG- (n=25), qPCR+IgM-IgG+ (n=29), qPCR+IgM+IgG+ (n=321), qPCR-IgM+IgG- (n=32), qPCR-IgM-IgG+ (n=40), and qPCR-IgM+IgG+ (n=291), according to different test outcomes. See Figure 1.
Figure 1.
Grouping situation.
There were 20 cases of fever (40.0%), 16 cases of combined hypertension (32.0%), 6 cases of mild (12.0%) symptoms and 39 cases of normal/slightly abnormal (78.0%) CT results in qPCR+IgM-IgG- group.
There were 14 cases of cough (56.0%), 8 cases of combined hypertension (32.0%), 7 cases of severe symptoms (28.0%) and 10 cases of normal/slightly abnormal (41.7%) CT results in qPCR+IgM+IgG- group.
There were 20 cases of cough (69.0%), 6 cases of combined hypertension (20.7%), 5 cases of severe symptoms (17.2%) and 16 cases of normal/slightly abnormal (55.1%) CT results in qPCR+IgM-IgG+ group.
There were 165 cases of fever (51.4%), 82 cases of combined hypertension (25.5%), 42 cases of severe symptoms (13.1%) and 165 cases of normal/slightly abnormal (52.4%) CT results in qPCR+IgM+IgG+ group.
There were 17 cases of cough (53.1%), 8 cases of combined hypertension (25.0%), 2 cases of severe symptoms (6.2%) and 12 cases of normal/slightly abnormal (38.7%) CT results in qPCR-IgM+IgG- group.
There were 26 cases of fever (65.0%), 9 cases of combined hypertension (22.5%), 5 cases of mild and severe symptoms (12.5%) and 18 cases of normal/slightly abnormal (45.0%) CT results in qPCR-IgM-IgG+ group.
There were 177 cases of fever (60.8%), 72 cases of combined hypertension (24.7%), 21 cases of severe symptoms (7.2%) and 121 cases of normal/little abnormal (41.6%) CT results in qPCR-IgM+IgG+ group.
Among them, patients with IgM+IgG+ were the majority (612 cases, 77.7%). They showed fever (342 cases, 55.9%), cough (318 cases, 52.0%), and fatigue (181 cases, 29.6%). Besides, there were 4 cases (8.0%) of pharyngalgia in qPCR+IgM-IgG- group. There were 1-3 cases of headache in the groups except for qPCR+IgM+IgG- group (0 case). There were no cases of tachycardia in the groups except for qPCR-IgM+IgG- group (1 case) and qPCR-IgM+IgG+ group (2 cases). Among the complications, the majority of IgM+ and IgG+ patients were combined with hypertension (154 cases, 25.2%), diabetes (64 cases, 10.5%), and coronary heart disease (29 cases, 4.7%). There were 1 case of congestive heart failure, and 1case of chronic kidney disease in both IgM+ and IgG+ patients. In the clinical classification, there were largest number of severe patients (63 cases, 10.3%) and critical patients (8 cases, 1.3%) in IgM+ and IgG+ groups. See Table 2.
Table 2.
Different nucleic acid and antibody detection results and the clinical type in COVID-19 patients
| qPCR+IgM-IgG- n=50 | qPCR+IgM+IgG- n=25 | qPCR+IgM-IgG+ n=29 | qPCR+IgM+IgG+ n=321 | qPCR-IgM+IgG- n=32 | qPCR-IgM-IgG+ n=40 | qPCR-IgM+IgG+ n=291 | |
|---|---|---|---|---|---|---|---|
| Age | |||||||
| Median (IQR) | 64.50 (45.75, 79.50) | 65.00 (52.50, 74.00) | 61.00 (39.50, 68.50) | 60.00 (50.00, 68.00) | 60.00 (51.25, 66.75) | 57.50 (45.25, 67.00) | 57.00 (48.00, 66.00) |
| Distribution no (%) | |||||||
| ≤17 yr | 1 (2.0) | 0 (0.0) | 1 (3.4) | 2 (0.6) | 0 (0.0) | 1 (2.5) | 0 (0.0) |
| 18-44 yr | 11 (22.0) | 4 (16.0) | 9 (31.0) | 60 (18.7) | 6 (18.8) | 8 (20.0) | 51 (17.5) |
| 45-64 yr | 13 (26.0) | 8 (32.0) | 6 (20.7) | 132 (41.1) | 14 (43.8) | 16 (40.0) | 149 (51.2) |
| 65-74 yr | 10 (20.0) | 8 (32.0) | 10 (34.5) | 89 (27.7) | 11 (34.4) | 12 (30.0) | 71 (24.4) |
| ≥75 yr | 15 (30.0) | 5 (20.0) | 3 (10.3) | 38 (11.8) | 1 (3.1) | 3 (7.5) | 20 (6.9) |
| Sex (n, %) | |||||||
| Male | 26 (52.0) | 12 (48.0) | 13 (44.8) | 107 (33.3) | 14 (43.7) | 19 (47.5) | 120 (41.2) |
| Female | 24 (48.0) | 13 (52.0) | 16 (55.2) | 214 (66.7) | 18 (56.3) | 21 (52.5) | 171 (58.8) |
| Signs and symptoms (n, %) | |||||||
| Fever | 20 (40.0) | 12 (48.0) | 15 (51.7) | 165 (51.4) | 16 (50.0) | 26 (65.0) | 177 (60.8) |
| Cough | 17 (34.0) | 14 (56.0) | 20 (69.0) | 164 (51.1) | 17 (53.1) | 18 (45.0) | 154 (52.9) |
| Fatigue | 11 (22.0) | 8 (32.0) | 7 (24.1) | 88 (27.4) | 14 (43.8) | 11 (27.5) | 93 (32.0) |
| Expectaration | 3 (6.0) | 2 (8.0) | 4 (13.8) | 16 (5.0) | 3 (9.4) | 4 (10.0) | 17 (5.8) |
| Asymptomatic | 5 (10.0) | 4 (16.0) | 1 (3.4) | 27 (8.4) | 0 (0.0) | 0 (0.0) | 7 (2.4) |
| Sore throat | 4 (8.0) | 1 (4.0) | 1 (3.4) | 5 (1.6) | 0 (0.0) | 0 (0.0) | 2 (0.7) |
| Shortness of breath | 2 (4.0) | 2 (8.0) | 1 (3.4) | 7 (2.2) | 2 (6.3) | 0 (0.0) | 8 (2.7) |
| Chest distress or Pectoralgia | 5 (10.0) | 3 (12.0) | 0 (0.0) | 30 (9.3) | 8 (25.0) | 6 (15.0) | 37 (12.7) |
| Dyspnea | 1 (2.0) | 0 (0.0) | 0 (0.0) | 2 (0.6) | 0 (0.0) | 0 (0.0) | 4 (1.4) |
| Myalgia | 0 (0.0) | 0 (0.0) | 0 (0.0) | 6 (1.9) | 0 (0.0) | 0 (0.0) | 6 (2.1) |
| Headache | 1 (2.0) | 0 (0.0) | 1 (3.4) | 3 (0.9) | 1 (3.1) | 1 (2.5) | 2 (0.7) |
| Nausea and vomiting | 0 (0.0) | 0 (0.0) | 0 (0.0) | 2 (0.6) | 0 (0.0) | 0 (0.0) | 1 (0.3) |
| Diarrhea | 0 (0.0) | 0 (0.0) | 0 (0.0) | 3 (0.9) | 0 (0.0) | 0 (0.0) | 2 (0.7) |
| Rhinorrhea | 0 (0.0) | 0 (0.0) | 0 (0.0) | 3 (0.9) | 0 (0.0) | 0 (0.0) | 0 (0.0) |
| Tachycardia | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 1 (3.1) | 0 (0.0) | 2 (0.7) |
| Coexisting disorder (n, %) | |||||||
| Hypertension | 16 (32.0) | 8 (32.0) | 6 (20.7) | 82 (25.5) | 8 (25.0) | 9 (22.5) | 72 (24.7) |
| Diabetes | 8 (16.0) | 2 (8.0) | 2 (6.9) | 38 (11.8) | 4 (12.5) | 5 (12.5) | 26 (8.9) |
| Coronary heart disease | 4 (8.0) | 1 (4.0) | 0 (0.0) | 22 (6.9) | 2 (0.6) | 3 (7.5) | 7 (2.4) |
| Cancer | 0 (0.0) | 1 (4.0) | 1 (3.4) | 11 (3.4) | 1 (0.3) | 0 (0.0) | 6 (2.1) |
| Cerebrovascular disease | 3 (6.0) | 2 (8.0) | 0 (0.0) | 8 (2.5) | 1 (0.3) | 1 (2.5) | 2 (0.7) |
| Chronic bronchitis | 1 (2.0) | 0 (0.0) | 0 (0.0) | 5 (1.6) | 1 (0.3) | 1 (2.5) | 3 (1.1) |
| Hepatitis B infection | 0 (0.0) | 0 (0.0) | 0 (0.0) | 1 (0.3) | 1 (0.3) | 0 (0.0) | 6 (2.1) |
| Asthma | 1 (2.0) | 0 (0.0) | 1 (3.4) | 2 (0.6) | 0 (0.0) | 0 (0.0) | 2 (0.7) |
| Chronic obstructive pulmonary disease | 0 (0.0) | 0 (0.0) | 1 (3.4) | 1 (0.3) | 0 (0.0) | 0 (0.0) | 2 (0.7) |
| Congestive heart failure | 2 (4.0) | 0 (0.0) | 0 (0.0) | 1 (0.3) | 0 (0.0) | 0 (0.0) | 0 (0.0) |
| Chronic renal disease | 1 (2.0) | 0 (0.0) | 0 (0.0) | 1 (0.3) | 0 (0.0) | 0 (0.0) | 1 (0.3) |
| Cirrhosis | 0 (0.0) | 0 (0.0) | 0 (0.0) | 1 (0.3) | 0 (0.0) | 0 (0.0) | 1 (0.3) |
| Clinical classification (n, %) | |||||||
| Mild | 6 (12.0) | 0 (0.0) | 3 (10.3) | 13 (4.0) | 0 (0.0) | 2 (5.0) | 11 (3.8) |
| Moderate | 38 (76.0) | 17 (68.0) | 20 (69.0) | 259 (80.7) | 30 (93.8) | 34 (85.0) | 258 (88.7) |
| Severe | 5 (10.0) | 7 (28.0) | 5 (17.2) | 42 (13.1) | 1 (3.1) | 3 (7.5) | 21 (7.2) |
| Critical | 1 (2.0) | 1 (4.0) | 1 (3.4) | 7 (2.2) | 1 (3.1) | 1 (2.5) | 1 (0.3) |
| Highest axilla-temperature during hospitalization (n, %) | |||||||
| Normal | 33 (68.8) | 11 (44.0) | 15 (55.6) | 243 (75.9) | 24 (75.0) | 31 (77.5) | 218 (75.2) |
| Low-grade fever | 14 (29.2) | 14 (56.0) | 10 (37.0) | 67 (20.9) | 8 (25.0) | 8 (20.0) | 66 (22.8) |
| Moderate fever | 1 (2.1) | 0 (0.0) | 1 (3.7) | 9 (2.8) | 0 (0.0) | 1 (2.5) | 6 (2.1) |
| High grade fever | 0 (0.0) | 0 (0.0) | 1 (3.7) | 1 (0.3) | 0 (0.0) | 0 (0.0) | 0 (0.0) |
| Leucocytes (×109/L) (n, %) | |||||||
| Median (IQR) | 6.05 (5.28, 6.63) | 5.50 (4.10, 6.70) | 6.00 (4.83, 6.80) | 5.80 (4.70, 7.00) | 5.40 (4.40, 6.50) | 6.10 (5.20, 6.80) | 5.50 (4.70, 6.60) |
| Decrease | 2 (4.0) | 3 (8.6) | 1 (3.6) | 11 (3.5) | 1 (3.2) | 1 (2.6) | 8 (2.9) |
| Normal | 47 (94.0) | 30 (85.7) | 26 (92.9) | 294 (93.3) | 30 (96.8) | 36 (92.3) | 263 (93.9) |
| Increase | 1 (2.0) | 2 (5.7) | 1 (3.6) | 10 (3.2) | 0 (0.0) | 2 (5.1) | 9 (3.212) |
| Neutrophils (×109/L) (n, %) | |||||||
| Median (IQR) | 3.83 (2.88, 4.19) | 3.34 (2.48, 4.69) | 3.76 (2.66, 4.42) | 3.49 (2.72, 4.35) | 2.98 (2.29, 3.71) | 3.59 (2.87, 4.31) | 3.31 (2.58, 4.13) |
| Decrease | 0 (0.0) | 1 (4.0) | 1 (3.6) | 12 (3.8) | 2 (6.5) | 1 (2.6) | 5 (1.8) |
| Normal | 47 (94.0) | 22 (88.0) | 26 (92.9) | 287 (91.1) | 28 (90.3) | 35 (89.7) | 264 (94.3) |
| Increase | 3 (6.0) | 2 (8.0) | 1 (3.6) | 16 (5.1) | 1 (3.2) | 3 (7.7) | 11 (3.9) |
| Lymphocytes (×109/L) (n, %) | |||||||
| Median (IQR) | 1.64 (1.16, 2.08) | 1.48 (1.05, 1.68) | 1.59 (1.25, 1.83) | 1.65 (1.32, 2.07) | 1.62 (1.26, 2.14) | 1.69 (1.41, 2.02) | 1.64 (1.29, 1.96) |
| Decrease | 9 (18.0) | 7 (28.0) | 5 (17.9) | 47 (14.9) | 4 (12.9) | 3 (7.7) | 44 (15.7) |
| Normal | 40 (80.0) | 18 (72.0) | 23 (82.1) | 263 (83.5) | 25 (80.6) | 36 (92.3) | 235 (83.9) |
| Increase | 1 (2.0) | 0 (0.0) | 0 (0.0) | 5 (1.6) | 2 (6.5) | 0 (0.0) | 1 (0.4) |
| Monocyte (×109/L) (n, %) | |||||||
| Median (IQR) | 0.38 (0.29, 0.43) | 0.38 (0.26, 0.45) | 0.36 (0.29, 0.48) | 0.37 (0.30, 0.45) | 0.36 (0.30,0.47) | 0.38 (0.32, 0.48) | 0.38 (0.29, 0.47) |
| No increase | 47 (94.0) | 21 (84.0) | 27 (96.4) | 299 (94.9) | 28 (90.3) | 35 (89.7) | 258 (92.1) |
| Increase | 3 (6.0) | 4 (16.0) | 1 (3.6) | 16 (5.1) | 3 (9.7) | 4 (10.3) | 22 (7.9) |
| Platelets (×109/L) (n, %) | |||||||
| Median (IQR) | 218.50 (180.75, 259.25) | 219.00 (179.00, 246.50) | 226.00 (196.25, 287.25) | 217.00 (180.00, 255.00) | 218.00 (174.00, 282.00) | 233.00 (172.00, 261.00) | 221.50 (179.50, 254.75) |
| Decrease | 3 (6.0) | 3 (12.0) | 3 (10.7) | 8 (2.5) | 2 (6.7) | 3 (7.7) | 10 (3.6) |
| Normal | 45 (90.0) | 21 (84.0) | 23 (82.1) | 293 (93.0) | 27 (90.0) | 35 (89.7) | 259 (92.5) |
| Increase | 2 (4.0) | 1 (4.0) | 2 (7.1) | 14 (4.4) | 2 (3.3) | 1 (2.6) | 11 (3.9) |
| Alanine aminotransferase (U/L) (n, %) | |||||||
| Median (IQR) | 16.70 (12.75, 31.70) | 22.40 (14.90, 34.5) | 15.90 (11.90, 26.75) | 18.80 (12.60, 30.38) | 18.05 (12.78, 35.75) | 17.70 (12.50, 33.80) | 23.35 (14.40, 37.53) |
| No Increase | 41 (89.1) | 21 (91.3) | 25 (100.0) | 281 (42.4) | 26 (92.9) | 36 (92.3) | 232 (86.6) |
| Increase | 5 (10.9) | 2 (8.7) | 0 (0.0) | 24 (7.9) | 2 (7.1) | 3 (7.7) | 36 (13.4) |
| Aspartate aminotransferase (U/L) | |||||||
| Median (IQR) | 16.40 (13.18, 20.45) | 18.80 (14.30, 22.70) | 14.10 (10.40, 20.70) | 15.80 (12.20, 20.95) | 16.00 (13.10, 25.78) | 17.90 (13.30, 23.50) | 16.65 (13.03, 22.45) |
| No increase | 42 (91.3) | 23 (100.0) | 25 (100.0) | 281 (92.1) | 26 (92.9) | 36 (92.3) | 244 (91.0) |
| Increase | 4 (8.7) | 0 (0.0) | 0 (0.0) | 24 (7.9) | 2 (7.1) | 3 (7.7) | 24 (9.0) |
| Erythrocyte sedimentation rate (mm/H) (n, %) | |||||||
| Median (IQR) | 22.00 (2.25, 69.00) | 15.00 (7.00, 93.00) | 11.00 (5.00, 26.00) | 29.50 (15.04, 62.00) | 63.00 (20.50, 102.75) | 54.50 (11.50, 77.75) | 24.00 (12.00, 57.00) |
| No increase | 8 (40.0) | 3 (60.0) | 5 (55.6) | 34 (28.8) | 1 (10.0) | 3 (37.5) | 41 (38.3) |
| Increase | 12 (40.0) | 2 (40.0) | 4 (44.4) | 84 (71.2) | 9 (90.0) | 5 (62.5) | 66 (61.7) |
| Interleukin-6 (pg/mL) (n, %) | |||||||
| Median (IQR) | 1.50 (1.50, 2.14) | 1.50 (1.50, 4.89) | 1.50 (1.50, 10.55) | 1.50 (1.50, 1.50) | 1.50 (1.50, 1.50) | 1.50 (1.50, 1.50) | 1.50 (1.50, 1.50) |
| No increase | 16 (100,0) | 13 (92.9) | 13 (76.5) | 138 (92.6) | 6 (85.7) | 13 (92.9) | 124 (94.7) |
| Increase | 0 (0.0) | 1 (7.1) | 4 (23.5) | 11 (7.4) | 1 (14.3) | 1 (7.1) | 7 (5.3) |
| C-reactive protein (mg/mL) (n, %) | |||||||
| Median (IQR) | 1.24 (0.58, 3.24) | 1.61 (5.49) | 0.96 (0.53, 2,87) | 1.29 (0.40, 3.01) | 1.60 (0.42, 3.49) | 1.83 (0.65, 5.32) | 1.31 (0.60, 2.96) |
| No increase | 44 (93.6) | 21 (84.0) | 23 (85.2) | 278 (90.6) | 28 (93.3) | 31 (83.8) | 244 (90.7) |
| Increase | 3 (6.4) | 4 (16.0) | 4 (13.8) | 29 (9.4) | 2 (6.7) | 6 (16.2) | 25 (9.3) |
| Procalcitonin (ng/mL) (n, %) | |||||||
| Median (IQR) | 0.40 (0.04, 0.06) | 0.04 (0.04, 0.05) | 0.04 (0.04, 0.05) | 0.40 (0.40, 0.50) | 0.40 (0.40, 0.60) | 0.40 (0.40, 0.50) | 0.40 (0.40, 0.60) |
| No increase | 22 (73.3) | 10 (83.3) | 17 (81.0) | 159 (78.7) | 13 (65.0) | 23 (79.3) | 127 (71.3) |
| Increase | 8 (26.7) | 2 (16.7) | 4 (19.0) | 43 (21.3) | 7 (35.0) | 6 (20.7) | 51 (28.7) |
| D-dimer (µg/L) (n, %) | |||||||
| Median (IQR) | 0.29 (0.12, 0.58) | 0.47 (0.24, 0.99) | 0.21 (0.16, 0.83) | 0.30 (0.18, 0.56) | 0.31 (0.21, 0.46) | 0.29 (0.17, 0.60) | 0.29 (0.20, 0.68) |
| No increase | 24 (88.9) | 8 (88.9) | 11 (84.6) | 193 (90.6) | 16 (88.9) | 19 (86.4) | 180 (93.8) |
| Increase | 3 (11.1) | 1 (11.1) | 2 (15.4) | 20 (9.4) | 2 (11.1) | 3 (13.6) | 12 (27.9) |
| Abnormalities on chest CT (n, %) | |||||||
| Ground glass shadow | 40 (80.0) | 23 (92.0) | 25 (86.2) | 298 (92.8) | 30 (93.8) | 37 (92.5) | 278 (95.5) |
| Reticulated nodule shadow | 21 (42.0) | 17 (68.0) | 15 (51.7) | 151 (47.0) | 23 (71.9) | 28 (70.0) | 158 (54.3) |
| Pulmonary fibrosis | 3 (6.0) | 6 (24.0) | 5 (17.2) | 42 (13.1) | 8 (25.0) | 9 (22.5) | 45 (15.5) |
| Consolidation | 1 (2.0) | 0 (0.0) | 3 (10.3) | 18 (5.6) | 3 (9.4) | 1 (2.5) | 23 (7.9) |
| Adjacent pleura thickening | 1 (2.0) | 0 (0.0) | 1 (3.4) | 7 (2.2) | 0 (0.0) | 0 (0.0) | 7 (2.4) |
| Thickening around the bronchus | 0 (0.0) | 0 (0.0) | 1 (3.4) | 4 (1.2) | 0 (0.0) | 0 (0.0) | 4 (1.4) |
| Pulmonary edema | 0 (0.0) | 0 (0.0) | 0 (0.0) | 1 (0.3) | 0 (0.0) | 0 (0.0) | 0 (0.0) |
| Pleural effusion | 2 (4.0) | 0 (0.0) | 0 (0.0) | 4 (1.2) | 0 (0.0) | 0 (0.0) | 0 (0.0) |
| Normal | 6 (12.0) | 0 (0.0) | 3 (10.3) | 13 (4.0) | 0 (0.0) | 2 (6.3) | 11 (3.8) |
| Lesion area (n, %) | |||||||
| Normal | 6 (12.0) | 0 (0.0) | 3 (10.3) | 13 (4.1) | 0 (0.0) | 2 (5.0) | 11 (3.8) |
| A few lesions | 33 (66.0) | 10 (41.7) | 13 (44.8) | 152 (48.3) | 12 (38.7) | 16 (40.0) | 110 (37.8) |
| Some lesions | 7 (14.0) | 5 (20.8) | 6 (20.7) | 72 (22.9) | 8 (25.8) | 14 (35.0) | 76 (26.1) |
| Many lesions | 3 (6.0) | 6 (25.0) | 3 (10.3) | 55 (17.5) | 9 (29.0) | 4 (10.0) | 70 (24.1) |
| Diffuse lesions | 1 (2.0) | 3 (12.5) | 4 (13.8) | 23 (7.3) | 2 (6.5) | 4 (10.0) | 24 (8.2) |
Note: Data are presented as medians (interquartile ranges, IQR), n (%). +: Positive. -: Negative; qPCR: reverse transcriptase polymerase chain reaction; IgM: Immunoglobulin M; IgG: Immunoglobulin G; yr: year; COVID-19: novel coronavirus pneumonia; Highest axilla-temperature during hospitalization: normal range <37.3°C; Leucocytes: normal range 3.5-9.5×109/L; Neutrophils: normal range 1.8-6.3× 109/L; Lymphocytes: normal range 1.1-3.2×109/L; Monocyte: normal range 0.1-0.6×109/L; Platelets: normal range 125.0-350.0×109/L; Alanine aminotransferase: normal range 0-55 U/L; Aspartate aminotransferase: normal range 5-34 U/L; Erythrocyte sedimentation rate: normal range 0-15 mm/H; Interleukin-6: normal range 0-10 pg/mL; C-reactive protein: normal range 0-10 mg/mL; Procalcitonin: normal range 0-0.05 ng/mL; D-dimer: normal range 0-1.5 µg/L.
Confirmation of nucleic acid antibodies
The sensitivities of qPCR, IgM, and IgG in COVID-19 patients were analyzed, and the results showed that the sensitivities of qPCR, IgM, and IgG were 53.9%, 84.9%, and 86.4%, respectively. Among them, the sensitivity of antibody detection for COVID-19 was higher than that of qPCR (84.9%, 86.4% vs. 53.9%, P<0.001). See Table 3.
Table 3.
Comparison of nucleic acid and antibody sensitivity of 788 COVID-19 patients
| qPCR | IgM | IgG | ||||
|---|---|---|---|---|---|---|
|
|
|
|
||||
| + | - | + | - | + | - | |
| Number | 425 | 363 | 669* | 119 | 681 | 107 |
| Sensitivity (%) | 53.9 | 84.9 | 86.4 | |||
Note: Compared with positive qPCR;
P<0.001.
Data are presented as n (%). +: Positive; -: Negative; IgM: Immunoglobulin M; IgG: Immunoglobulin G; COVID-19: novel coronavirus pneumonia.
Comparison of clinical characteristics between IgM+ and IgM- COVID-19 patients
The sensitivity of IgM was significantly higher than that of nucleic acid testing, which played an important role after virus infection. IgM antibodies may have important clinical value in COVID-19 patients, so the relationship between IgM antibody detection and the clinical characteristics of COVID-19 patients was analyzed. The results showed that there were significant differences between IgM+ patients and IgM- patients in terms of age distribution, gender, sore throat, clinical classification, and CT findings (P<0.05). See Table 4.
Table 4.
Comparison of clinical characteristics of IgM positive and IgM negative patients with COVID-19
| IgM | P | ||
|---|---|---|---|
|
| |||
| + (n=669) | - (n=119) | ||
| Age | 59.00 (49.00, 67.00) | 62.00 (44.00, 69.00) | |
| Distribution (n, %) | <0.001 | ||
| ≤17 yr | 2 (0.3) | 3 (2.5) | |
| 18~44 yr | 121 (18.1) | 28 (23.5) | |
| 45~64 yr | 303 (45.3) | 35 (29.4) | |
| 65~74 yr | 179 (26.8) | 32 (26.9) | |
| ≥75 yr | 64 (9.6) | 21 (17.6) | |
| Sex (n, %) | 0.025 | ||
| Male | 253 (37.8) | 58 (48.7) | |
| Female | 416 (62.2) | 61 (51.3) | |
| Signs and symptoms (n, %) | |||
| Fever | 370 (55.3) | 61 (51.3) | 0.517 |
| Cough | 349 (52.2) | 55 (46.2) | 0.232 |
| Fatigue | 203 (30.3) | 29 (24.4) | 0.188 |
| Expectaration | 38 (5.7) | 11 (9.2) | 0.138 |
| Asymptomatic | 38 (5.7) | 6 (5.0) | 0.780 |
| Sore throat | 8 (1.2) | 5 (4.2) | 0.048 |
| Shortness of breath | 34 (5.1) | 4 (3.4) | 0.419 |
| Myalgia | 11 (1.6) | 0 (0.0) | 0.386 |
| Chest distress or Pectoralgia | 74 (11.1) | 10 (8.4) | 0.387 |
| Headache | 6 (0.9) | 3 (2.5) | 0.285 |
| Dyspnea | 6 (0.9) | 1 (0.8) | 1.000 |
| Nausea and vomiting | 3 (0.4) | 0 (0.0) | 1.000 |
| Diarrhea | 5 (0.7) | 0 (0.0) | 1.000 |
| Rhinorrhea | 3 (0.4) | 0 (0.0) | 1.000 |
| Tachycardia | 3 (0.4) | 0 (0.0) | 1.000 |
| Coexisting disorder (n, %) | |||
| Hypertension | 170 (25.4) | 31 (26.1) | 0.883 |
| Diabetes | 71 (10.6) | 15 (12.6) | 0.521 |
| Coronary heart disease | 32 (4.8) | 7 (5.9) | 0.611 |
| Cancer | 19 (2.8) | 1 (0.8) | 0.336 |
| Cerebrovascular disease | 13 (1.9) | 4 (3.4) | 0.523 |
| Chronic bronchitis | 9 (1.3) | 2 (1.7) | 0.482 |
| Hepatitis B infection | 8 (1.2) | 0 (0.0) | 0.614 |
| Asthma | 4 (0.6) | 2 (1.7) | 0.497 |
| Chronic obstructive pulmonary disease | 3 (0.4) | 1 (0.8) | 1.000 |
| Congestive heart failure | 1 (0.1) | 2 (1.7) | 0.091 |
| Chronic renal disease | 2 (0.3) | 1 (0.8) | 0.940 |
| Cirrhosis | 2 (0.3) | 0 (0.0) | 1.000 |
| Clinical classification (n, %) | 0.036 | ||
| Mild | 24 (3.6) | 11 (9.2) | |
| Moderate | 564 (84.3) | 92 (77.3) | |
| Severe | 71 (10.6) | 13 (10.9) | |
| Critical | 10 (1.5) | 3 (2.5) | |
| Highest axilla-temperature during hospitalization (n, %) (normal range <37.3°C) | 0.243 | ||
| Normal | 496 (74.4) | 79 (68.7) | |
| Low-grade fever | 155 (23.2) | 32 (27.8) | |
| Moderate fever | 15 (2.2) | 3 (2.6) | |
| High-grade fever | 1 (0.1) | 1 (0.9) | |
| Leucocytes (×109/L; normal range 3.5-9.5) (n, %) | |||
| Median (IQR) | 5.60 (4.70, 6.80) | 6.00 (5.20, 6.70) | 0.869 |
| Decrease | 23 (3.5) | 4 (3.4) | |
| Normal | 607 (93.2) | 109 (94.0) | |
| Increase | 21 (3.2) | 4 (3.4) | |
| Neutrophils (×109/L; normal range 1.8-6.3) (n, %) | |||
| Median (IQR) | 3.37 (2.65, 4.26) | 3.74 (2.83, 4.29) | 0.597 |
| Decrease | 20 (3.1) | 2 (1.7) | |
| Normal | 601 (92.3) | 108 (92.3) | |
| Increase | 30 (4.6) | 7 (6.0) | |
| Lymphocytes (×109/L; normal range 1.1-3.2) (n, %) | |||
| Median (IQR) | 1.63 (1.27, 2.20) | 1.64 (1.29, 1.99) | 0.892 |
| Decrease | 102 (15.7) | 17 (14.5) | |
| Normal | 541 (83.1) | 99 (84.6) | |
| Increase | 8 (1.2) | 1 (0.9) | |
| Monocyte (×109/L; normal range 0.1-0.6) (n, %) | |||
| Median (IQR) | 0.37 (0.30, 0.46) | 0.38 (0.30, 0.46) | 0.713 |
| No Increase | 606 (93.1) | 110 (94.0) | |
| Increase | 45 (6.9) | 7 (6.0) | |
| Platelets (×109/L; normal range 125.0-350.0) (n, %) | |||
| Median (IQR) | 220 (180, 255) | 225.00 (182.00, 261.50) | 0.114 |
| Decrease | 23 (3.5) | 9 (7.7) | |
| Normal | 602 (92.5) | 103 (88.0) | |
| Increase | 26 (4.0) | 5 (4.3) | |
| Alanine aminotransferase (U/L; normal range 0-55) (n, %) | |||
| Median (IQR) | 21.00 (13.35, 34.30) | 16.90 (12.45, 30.75) | 0.332 |
| No Increase | 560 (89.7) | 102 (92.7) | |
| Increase | 64 (10.3) | 8 (7.3) | |
| Aspartate aminotransferase (U/L; normal range 5-34) (n, %) | |||
| Median (IQR) | 16.20 (12.70, 21.68) | 16.00 (12.73, 21.60) | 0.551 |
| No Increase | 574 (92.0) | 103 (93.6) | |
| Increase | 50 (8.0) | 7 (6.4) | |
| Erythrocyte sedimentation rate (mm/H; normal range 0-15) | |||
| Median (IQR) | 26.00 (12.00, 62.00) | 22.00 (8.00, 55.50) | 0.218 |
| No Increase | 79 (32.9) | 16 (43.2) | |
| Increase | 161 (67.1) | 21 (56.8) | |
| Interleukin-6 (pg/mL; normal range 0-10) (n, %) | |||
| Median (IQR) | 1.5 (1.5, 1.5) | 1.50 (1.50, 2.64) | 0.495 |
| No increase | 281 (93.4) | 42 (89.4) | |
| Increase | 20 (6.6) | 5 (10.6) | |
| C-reactive protein (mg/mL; normal range 0-10) (n, %) | |||
| Median (IQR) | 1.31 (0.51, 3.07) | 1.22 (0.60, 3.41) | 0.472 |
| No increase | 571 (90.5) | 98 (88.3) | |
| Increase | 60 (9.5) | 13 (11.7) | |
| Procalcitonin (ng/mL; normal range 0.0-0.05) (n, %) | |||
| Median (IQR) | 0.04 (0.04, 0.58) | 0.40 (0.40, 0.50) | 0.635 |
| No increase | 309 (75.0) | 62 (77.5) | |
| Increase | 103 (25.0) | 18 (22.5) | |
| D-dimer (µg/L; normal range 0.0-1.5) (n, %) | |||
| Median (IQR) | 0.30 (0.20, 0.58) | 0.27 (0.15, 0.54) | 0.210 |
| No increase | 397 (91.9) | 54 (87.1) | |
| Increase | 35 (8.1) | 8 (12.9) | |
| Abnormalities on chest CT (n, %) | |||
| Ground glass shadow | 629 (94.0) | 102 (85.7) | 0.001 |
| Reticulated nodule shadow | 349 (52.2) | 64 (53.8) | 0.745 |
| Pulmonary Fibrosis | 101 (15.1) | 17 (14.3) | 0.819 |
| Consolidation | 44 (6.6) | 5 (4.2) | 0.323 |
| Adjacent pleura thickening | 14 (2.1) | 2 (1.7) | 1.000 |
| Thickening around the bronchus | 8 (1.2) | 1 (0.8) | 1.000 |
| Pulmonary edema | 1 (0.1) | 0 (0.0) | 1.000 |
| Pleural effusion | 4 (0.6) | 2 (1.7) | 0.229 |
| Normal | 24 (3.6) | 11 (9.2) | 0.006 |
| Lesion area (n, %) | 0.001 | ||
| Normal | 24 (3.6) | 11 (9.2) | |
| A few lesions | 284 (42.9) | 62 (52.1) | |
| Some lesions | 161 (24.3) | 27 (22.7) | |
| Many lesions | 141 (21.3) | 10 (8.4) | |
| Diffuse lesions | 52 (7.9) | 9 (7.6) | |
Note: Data are presented as medians (interquartile ranges, IQR), n (%). +: Positive; -: Negative; qPCR: reverse transcriptase polymerase chain reaction; IgM: Immunoglobulin M; IgG: Immunoglobulin G; yr: year; COVID-19: novel coronavirus pneumonia.
Discussion
COVID-19 is a globally spreading respiratory disease, and its spread has reached the level of pandemic, posing a great threat to the global economy and human health [13]. The total mortality is about 3.46%, and the incubation period is long (0-24 days), which causes certain difficulties in the management of COVID-19 [14]. In this study, the clinical value related to the diagnosis indicators of COVID-19 patients was studied, which is of great significance for the diagnosis and effective management.
In this study, 788 COVID-19 patients with a median age of 59.5 years were included. Majority of patients were in the age group over 45 years (80.5%), while patients under 17 years old were the least (0.6%), suggesting that middle-aged and elderly people over 45 were at high risk of COVID-19. It was pointed out that COVID-19 was mainly concentrated in 30-79 years old patients (86.6%), which was similar to our results [15]. In this study, it was found that the main symptoms of patients were fever, cough, and fatigue, which was similar to the research results of Xu et al. [16]. In this study, the patients included were accompanied with comorbidities such as hypertension, diabetes, and coronary heart disease, which were similar to the study of Zhou et al. [17]. What’s more, in this study, ordinary and severe patients accounted for the vast majority (93.9%), while the proportion of mild patients was very small (6.1%).
In addition to analyzing the clinical characteristics of COVID-19 patients, the clinical value related to COVID-19 diagnosis indicators (qPCR and IgM and IgG antibodies) were also focused on in this study. qPCR testing plays a very important role in the diagnosis of COVID-19, and virus testing is mainly performed through nasopharyngeal swabs [18,19]. Serum IgM and IgG are specific antibodies produced during the 2019-nCoV infection period, and can be used as auxiliary diagnostic tools when qPCR is negative [20,21]. Based on the different test results of qPCR and IgM and IgG antibodies, we divided the COVID-19 patients into seven groups for relevant clinical value analysis. The results showed that the qPCR+IgM-IgG- group had more patients with normal appearances and a few lesions in CT results (78.0%), which may be related to the early stage of the disease. Besides, we found that there were as many as 612 (77.7%) patients with both antibodies positive (IgM+IgG+), including 63 (10.3%) severe patients and 8 critically ill patients, which may be related to the acute infection of these patients. There were asymptomatic patients (5.6%) in the double antibody positive group. Asymptomatic patients make the prevention and management of COVID-19 more difficult. The combined detection of qPCR and IgM and IgG antibodies can help avoid the missed detection of asymptomatic COVID-19 [22,23]. As for the analysis of the sensitivities of qPCR, IgM and IgG antibodies to detect COVID-19, the sensitivity of antibody was higher than that of qPCR (84.9%, 86.4% vs. 53.9%). Although the epidemic situation in China has been clearly controlled, the global COVID-19 cases are still increasing rapidly. With insufficient knowledge of new diseases, the prospect of global anti-epidemic is still unknown. When testing resources are sufficient, it is recommended that nucleic acid antibodies are tested at the same time to reduce the missed diagnosis rate, which is of great significance for epidemic prevention and control.
We finally analyzed the relationship between IgM antibodies and the clinical parameters of COVID-19 patients. The data showed that there were significant differences between IgM+ patients and IgM- patients in terms of age distribution, gender, sore throat, clinical classification, and CT findings, suggesting that IgM antibodies had certain guiding significance in the clinical diagnosis and treatment process. Among them, the proportion of sore throat in IgM+ patients was significantly less than that of IgM- patients. It can be explained that the early colonization of the virus occurred in the upper respiratory tract, while IgM antibodies had not yet been produced at this time. CT results showed that there were 629 ground glass shadows in the IgM+ group, accounting for 94.0%, which was significantly higher than that in the IgM- group. The ground glass shadow is a typical CT feature of COVID-19 patients, which may indicate that COVID-19 patients are in the acute infection stage, and the lesions are mainly manifested as acute inflammatory exudation [24]. In addition, 24 cases of IgM+ group had normal CT, accounting for 3.6%, which was significantly lower than that of IgM- group, suggesting that IgM+ group may be related to severe CT manifestations of COVID-19 patients.
Although this study analyzed the clinical value related to the diagnosis indicators of COVID-19 patients, there are still some limitations. First of all, the medical record data came from patients with confirmed COVID-19, and we could only calculate the sensitivity of nucleic acid and antibody detection, but could not provide specificity results. Second, we did not do the comparison of the data of undiagnosed patients, which further limits the clinical value of the analysis. The latest developments of COVID-19 will be continued to follow up in the future, and we will make improvements and perform new research around the above points when conditions permit.
In summary, we analyzed for the first time the relevant clinical value of the diagnostic indicators of COVID-19 patients, including the clinical value of qPCR, IgM and IgG antibodies in clinical features, laboratory indicators, and CT features. We focused on mining clinical value of IgM antibody in COVID-19 patients. The auxiliary diagnostic value of IgM antibody in COVID-19 patients is beneficial to avoid missed diagnosis of qPCR- patients, and its clinical value in COVID-19 patients is of certain importance for the management of COVID-19 patients.
Disclosure of conflict of interest
None.
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