The novel coronavirus SARS-CoV-2 is the seventh known species of coronavirus, infectious to human beings. The pandemic COVID-19 spread all over the world with an unprecedented spreading rate after its first appearance in Wuhan, China. As a novel viral disease there in no antiviral treatment or vaccine for the COVID-19. At present, the early detection and the quarantine of infected patients are the ways to stop the spreading of the disease. This review will discuss about the current invitro diagnostic methods used worldwide for the early and accurate diagnosis of COVID-19. Currently the nucleic acid based polymerase chain reaction is used as the reliable diagnostic platform and antigen/antibody detection immunoassays are playing the role of screening tests for early detection and prognosis in COVID-19 treatment.

Upon SARS CoV-2 infection, humoral immune system triggers production of anti-SARS CoV-2 IgM and IgG antibodies. Currently, antibodies against SARS CoV-2 spike protein receptor binding domain play a central role in disease protection, making them potential target for in vitro diagnostics applications. This study determines the expression level and sustainability of anti-receptor binding domain (RBD) SARS CoV-2 IgG in post COVID-19 patients. Anti-RBD SARS CoV-2 IgG antibodies in patient serum were analysed by standardised indirect ELISA using SARS CoV-2 spike receptor binding domain protein and HRP conjugated anti-human IgG antibody (anti-h IgG). The study was conducted using 35 adult patient samples with confirmed SARS CoV-2 infection. Additionally, correlation between antibody response after each stage and disease symptoms in post COVID-19 patients were studied. Maximum antibody titre was seen at Day 40 and decreased relatively to Day 180 in antibody positive samples when compared with controls. Overall, more IgG antibody expression is observed in patients who suffered from loss of smell and taste at Day 40. 71% of the positive subjects in this study showed high SARS CoV-2 IgG antibody concentration of above 10 ng/mL and 37% showed strong antibody concentration above 20 ng/mL at the peak of seroconversion.

Rationale: COVID-19 patients, especially immunocompromised or severely ill, have a higher probability of suffering from invasive fungal infections. Patient Concerns: A 41-years-old male reported with pain and heaviness in the face for the past 20 days. Patient had tested COVID-19 positive 20 days back and was recently diagnosed with diabetes mellitus. On histopathological examination numerous hyphae resembling mucor and asper fungi were evident. Diagnosis: Chronic invasive aspergillosis with fulminant mucormycosis sparing palate. Treatment: Since the lesion was spreading very rapidly the patient was referred to an isolation facility for further management. Outcomes: We have postulated few hypothesis for the coinfection of aspergillosis and mucormycosis in our patient. Take-away Lessons: It is important for the clinicians to systematically screen post COVID-19 patients for fungal infections, especially in immunocompromised and severely ill patients.