Abstract:
Background With the deepen understanding of COVID-19 's diagnosis and disease classification, more attention has been paid to the clinical value of serum antibodies.
Objective To analyze the dynamic changes of specific antibodies in COVID-19 patients and its relationship with the prognosis of critical patients, and explore the immune mechanism of critical patients, so as to provide reference for the diagnosis, early classification and improvement of prognosis of COVID-19 patients.
Methods A retrospective survey was conducted on 1 921 COVID-19 patients (including 952 males and 969 females) admitted to Huoshenshan Hospital in Wuhan City from February 2, 2020 to April 15, 2020. According to the clinical classification criteria in Diagnosis and Treatment Protocol for Novel Coronavirus Pneumonia, the patients were divided into common group (n=1 280), severe group (n=591) and critical group (n=50), and their baseline characteristics and laboratory results were compared. The dynamic changes of antibody positive rate and titer with the course of disease were observed. Furthermore, the relationship between 2019-nCoV antibody expression and laboratory results as well as nucleic acid test results were analyzed.
Results The positive rate of IgM reached a peak of 80.9% at the 6th week after onset, and then showed a downward trend. The positive rate of IgG reached 90.69% at the 4th week, 100% at the 9th week, and remained at a high level. The IgM of common and severe patients increased at first and then decreased while the IgM in critical patients was delayed but strongly reacted, and decreased continuously. The average titer of IgM was severe group > common group > critical group 53.18(27.44, 105.13) > 46.48(23.39, 91.08) > 38.54 (19.6, 64.23), P < 0.05. The IgG of critical patients appeared the latest, and the average titer was significantly lower than the other two groups 102.59(66.48,172.34) vs 154.08 (86.25, 184.87), 153.1 (87.88, 184.6) (P < 0.05). The IgG of the three groups showed a continuous increase. With the aggravation of the severity of the disease, neutrophil count, white blood cell count and procalcitonin increased significantly, but there was no significant difference in nucleic acid negative conversion time among the three groups 36.0 (27.0, 45.0) vs 36.0 (27.0, 44.0) vs 41.0 (29.0, 48.0)(P＞0.05).
Conclusion Antibody detection can supplement nucleic acid detection for diagnosis, and the differential expression of antibodies in common, severe and critical patients is closely related to the immune status of patients. The relationship between nucleic acid negative time and the severity of the disease needs to be further studied.
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