Role of IgG and IgM and proinflammatory non-specific markers in the diagnosis and prognosis of COVID-19 patients stratified by number of positive SARS-CoV-2 genes.

BACKGROUND: A prompt set of suitable biomarkers is needed in suspected COVID-19 patients. This study aims to assess patients positive for one or more gene associated with the C reactive protein (CRP) and procalcitonin (PCT) as non-specific pro-inflammatory markers and IgG and IgM kinetic as specific diagnostic and prognostic tools in SARS-CoV-2 RT-PCR positive patients. METHODS: We enrolled 101 patients within a two month time span (March 26th, 2020 to May 31st, 2020). A reverse transcription-Real-Time PCR assay on nasopharyngeal/oropharyngeal swabs was used for SARS-CoV-2 identification. Serum anti-SARS-CoV-2 IgM and IgG were measured by enzyme immunoassay, PCT levels by Enzyme linked fluorescent assay (ELFA)and CRP by nephelometry. RESULTS: We found that older patients were significantly associated with a worse prognosis. Serum IgM levels were significantly lower during the late stage of the disease, regardless of the presence of one or three genes and patients' outcome. On the contrary, IgG levels exhibited a higher concentration in the late phases of the illness, regardless of the gene found or patients' prognosis. With the exception of the very first sample tested, an increase in CRP in surviving patients (both one and three genes) and a time-dependent decrease of deceased patients CRP was found. PCT levels were always within the normal reference range. The difference between one gene and three genes patients was significant during late disease stages regarding IgG levels and also between three genes survivors versus three genes deceased, where the IgG levels were progressively increasing over time. CONCLUSIONS: The relevant finding of the present study is the significant and consistent increase of IgG and IgM in deceased patients. The associated evaluation of antibody kinetics and non specific inflammatory markers (CRP and PCT) in positive patients stratified according to the presence of one gene or three genes could help the clinician in both the diagnosis and prognosis of COVID-19 patients.