A new coronavirus, SARS-CoV-2, was identified in Wuhan, China in late 2019. The virus, which causes Coronavirus Disease 2019 (COVID-19), has contributed to significant morbidity (illness) and mortality (death), as well as severe public health and economic effects, among other impacts.
Initial diagnosis in symptomatic patients, should be considered primarily in those with new-onset fever and/or respiratory tract symptoms (eg, cough, dyspnea) smell or taste disturbances, myalgias, and diarrhoea, Resides in or has travelled within the prior 14 days, extrapulmonary complications cardiac injury, ischemic stroke and other thromboembolic events, and inflammatory complications (eg, the multisystem inflammatory syndrome in children).
Real-Time RT-PCR is the gold standard test for detecting cases of COVID-19. The test requires oropharyngeal/nasopharyngeal samples and a specialized laboratory setup with specific biosafety and biosecurity precautions to be followed. The average time taken is around 4-5 hours from receipt of the sample to getting the result. The advantage of this platform lies in its accuracy of detection.
A positive result confirms the diagnosis of COVID-19, however, in some patient’s test may stay positive but does not necessarily indicate ongoing infectiousness.
For many individuals, a single negative NAAT result is sufficient to exclude the diagnosis of COVID-19. However. If initial testing is negative but the suspicion for COVID-19 remains; it is generally performed 24 to 48 hours after the initial test.
For patients who present three to four weeks into the course of illness and have negative NAAT, checking a serologic test may be informative If serology is performed in this setting, we suggest an IgG test; a total antibody test is also likely useful, but data are limited for this situation.
Indeterminate PCR test indicates that only one of the two or more genes that the NAAT test targets was identified. These results can be considered presumptive positive results, given the high specificity of NAAT assays. If the patient is early in the disease course, repeat testing can be helpful to confirm.
The TrueNat and CBNAAT (Cartridge-based Nucleic acid test) systems have also been deployed for diagnosis of COVID-19 in view of the availability of customized cartridges. These platforms have a quick turnaround time (30 -60 minutes) but only 1-4 samples can be tested in one run, limiting the maximum numbers that can be tested to 24-48 samples/day only. The viral lysis buffer that comes with the COVID-19 cartridges inactivates the virus and poses a minimum biosafety hazard. Safety is further augmented by the closed nature of these platforms and minimum sample handling. These features have facilitated the use of these platforms at grass root level thereby increasing access to testing.
Rapid Point-of-Care (PoC) Antigen Detection Test (for diagnosis along with RT-PCR) if reliable would be valuable at field level for early detection of infection and quick containment. Most of such tests have relatively moderate sensitivity but high specificity. A positive test should be considered as a true positive whereas all symptomatic individuals testing negative through the rapid antigen test should be confirmed with a real-time PCR test.
Other investigations like Radiological changes seen in HRCT chest are pure ground-glass opacities (GGOs) and patchy consolidation surrounded by GGOs. Critical cases had multiple consolidation surrounded by a wide range of GGOs distributed in the whole lung fields.
Laboratory investigations show an increase in IL-6 levels has previously been observed in patients with respiratory dysfunction.An increase in D-dimer and fibrinogen concentrations in the early stages of COVID-19 disease a 3 to 4-fold rise in D-dimer levels are linked to poor prognosis
Hence as recommended by CDC testing immediately after the exposure is to quickly identify infection, Track, test, treat and segregate further to prevent the spread of Infection. .
