COVID-19 is caused by Severe acute respiratory syndrome (SARS) coronavirus 2 (SARS-CoV-2), the prototype virus of the family Coronaviridae which preferentially infects respiratory tract cells, but also affect other organs such as; brain, conjunctiva, heart, liver, lungs, kidneys and pharynx (1,2). COVID-19, ‘CO’ stands for ‘corona,’ ‘VI’ for ‘virus,’ and ‘D’ for disease. Formerly, this disease was referred to as “2019 novel coronavirus” or “2019-nCoV”. The first case of pneumonia patient with unknown cause was officially reported on December 8, 2019. Several cases of pneumonia infected by 2019-nCoV were found in Wuhan, Hubei Province. World Health Organization announced its outbreak as 6th public health emergency of international concern in January 2020, but two months later it was declared as pandemic. As a large viral family, the coronaviruses can cause major diseases such as colds, Middle East Respiratory Syndrome (MERS), and severe acute respiratory syndrome (SARS). 2019-nCoV is a kind of new coronavirus which has not been found in human before. It belongs to novel β-coronavirus with an envelope, round or oval particles and is often polymorphic, with a diameter of 60-140nm. WHO stated global number of COVID-19 positive cases have been mounted to 50,266,033 (including 21,730,622 cases from America, 13,366,839 cases from Europe, 9,697,585 in South-East Asia, 3,337,885 in Eastern Mediterranean, 1,362,566 cases in Africa, and 769,795 in Western Pacific) among which 1,254,567 deaths were reported worldwide (3).

The SARS-CoV-2 contain four major structural proteins; nucleocapsid, matrix core protein, envelop, and glycoprotein spike surface. SARS-CoV-2 utilizes angiotensin‐converting enzyme 2 ACE2 receptor expressed on Alveolar type 2 progenitor (AT2) epithelial cells. The virus penetrates host cell through clathrin- and caveolae- independent endocytic pathways and via host cell directed network of G-protein-coupled receptors it may activate c-Jun N-terminal Kinase (JNK) and Janus Tyrosine Kinase (JAK)-Signal Transducer and Activator of Transcription (STAT) pathways, for enhanced viral replication (4).

Those who are infected by COVID-19 often have the symptoms of fever, weakness and dry cough. Few patients have the symptoms of nasal congestion, runny nose, sore throat and diarrhea. Severe patients often suffer from dyspnea and/or hypoxemia one week after onset, and very severe patients rapidly progress to acute respiratory distress syndrome, septic shock, intractable metabolic acidosis and coagulation disorders. Notably, patients with severe or critically ill patients may have moderate to low fever or even no obvious fever. Patients with mild symptoms just have slight fever and weakness without pneumonia. Patient without symptoms have been also reported. When cultured in vitro separately, 2019-nCoV can be found in human respiratory epithelial cells in about 96 hours; when cultured in Vero E6 and Huh-7 cell lines separately, about 6 days. It is known that COVID-19 is mainly transmitted through respiratory droplets and contact. Routes of transmission such as aerosol and digestive tract have yet to be investigated further (3,4).

Rapid diagnostic tests (RDTs) are easy to use, cheaper and safe to use, but there are several potential concerns regarding validation and accurate performance of these diagnostic assays (5). Previously, in comparison to gold-standard PCR positive patients, we showed the sensitivities of nasopharyngeal swab (52%) and saliva based (21%) SARS-CoV-2 antigen based rapid diagnostic kits in Pakistan (6). To validate further the accurate diagnosis of nasopharyngeal swab rapid diagnostic kits we further evaluated COVID-19 antigen based kits.