Laboratory Diagnosis of COVID-19

COVID-19 is a novel virus and despite the predilection for the respiratory tract, it has the potential of becoming a multi-systemic disease. With its emergence arose the need for prompt and appropriate diagnostic and prognostic molecular tests that cut across all sections of laboratory medicine. A proper laboratory diagnosis is critical in order to aid clinical management and control the disease transmission.

The ideal specimen for the detection of SARS-CoV-2 is bronchoalveolar lavage but this is quite an invasive specimen to obtain. There is a high risk of infecting the caregiver via aerosols generated during the procedure. Instead, the WHO recommends nasal and oropharyngeal swabs for routine testing using flocked nylon swabs. Lung biopsy is reserved for post-mortem cases.

During sample collection, it is crucial that appropriate personal protective equipment (PPE) is worn and that the procedure is performed in a room with adequate ventilation. The best transport medium is the viral transport medium (VTM) stored on ice.

Sample processing should be performed in a biosafety level two (BSL-2) laboratory facility (or higher) due to the high infectivity of the virus. The widely accepted test for the early detection of SARS-CoV-2 RNA is the Nucleic Acid Amplification Test (NAAT) using reverse transcriptase quantitative polymerase chain reaction (RT-qPCR). Other modalities include antigen-based tests and viral cultures.

Concurrently, samples should also be obtained for biochemical tests due to the "cytokine storm" associated with severe COVID-19 infection. Hepatic and renal biomarkers including inflammatory markers such as Interleukin-6 (IL-6) and Tumor Necrosis Factor-
(TNF-
) should be assayed as they could be elevated in severe manifestations of the disease.

The organ in the eye of the storm are the lungs and they were extensively studied during the pandemic. In COVID-19 infection, they may grossly appear to be heavy, congested and edematous with cut sections that show patchy areas of hemorrhage and focal areas of vascular plugging. Generally, the pulmonary pathologic features appear to be consistent with early/organizing diffuse alveolar damage (DAD).

The utility of laboratory tests for screening, diagnosis, monitoring and prognostication of COVID-19 is central to the management of this emerging infectious disease.