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Diagnosis

Diagnosis. based primarily on clinical symptoms and using laboratory test results as a secondary basis. the history of recent travel to high risk areas or history of close contacts with person with SARS Chest x-ray PCR testing, Seroconversion by ELISA or IFA and Virus isolation.

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Diagnosis

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  1. Diagnosis

  2. based primarily on clinical symptoms and using laboratory test results as a secondary basis. • the history of recent travel to high risk areas or history of close contacts with person with SARS • Chest x-ray • PCR testing,Seroconversion by ELISA or IFA and Virus isolation

  3. PCR testing • For PCR testing, there are at least 2 different clinical specimens needed (eg:nasopharyngealand stool.) Besides that, there can also be the same clinical specimen collected on 2 or more days during the course of the illness for example 2 or more nasopharyngeal aspirates are obtained for diagnosis • The peak detection rate for SARS-associated coronavirusdepends on the type of the specimen obtained. • week 2after illness onset for respiratory specimens • weeks 2 to 3 for stool or rectal swab specimens • week 4 for urine specimens. • If a positive PCR result has been obtained, it should be confirmed by repeating the PCR using the original sample or having the same sample tested in a second laboratory. Amplifying a second genome region could further increase test specificity.

  4. Seroconversion by ELISA or IFA: • ELISA or IFA is a negative antibody test on acute serum followed by positive antibody test on convalescent serum. • Antibodies against SARS-CoV become detectable with high sensitivity around 10 days after the onset of infection, but they can be undetectable prior to this by current testing methods. • Positive antibody test results indicate that there has been an infection with SARS-CoV. • Seroconversionfrom negative to positive, or a four-fold rise in antibody titre in the serum of a convalescent patient compared with that patient’s serum during acute illness, denotes a recent infection. • A negative serological result 21 days after onset of symptoms indicates absence of SARS-CoV infection. Cross-reactions with antibodies to other agents (including the human coronaviruses HCoV-229E and HCoV-OC43) are not known. • Antibody determination using IFA or ELISA was the most reliable method for identifying infections with SARS-CoV.

  5. Virus isolation • Patient specimens such as respiratory secretions, blood, or stool can be inoculated in suitable cell lines for growth of the infectious agent. • Vero cells have been used for culture. After isolation, the virus has to be confirmed and this is usually done with nucleic acid based tests. • Positive results indicate presence of viable SARS-CoV, whilst negative cell culture results do not exclude SARS. • These viruses were originally isolated in organ cultures of human embryonic trachea and subsequently grown in tissue culture in fibroblasts. • Although most coronaviruses are highly species specific,ableto employ a larger variety of receptors on the cell surface,showa marked degree of tissue tropisminfluenced by both host cell surface characteristics and by viral S-glycoprotein

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