Some people are tested negative (false negatives) in a Rapid Diagnostic Test (RDT) and sent home. — .But later, Polymerase Chain Reaction (PCR) report confirmed that they are infected with novel corona-virus. Is it simply due to the timing of the tests or some human and equipment errors are associated with these sorts of reports ?
I think rapid test is not active to discover the true positive case in COVID-19 situation because its affected by many factors such as the storage manner
I think what your are referring to is a story about antibody testing that was in the news today and/or yesterday. Normally these assays test for both IgM (innate) and IgG (adaptive) antibodies present in the individual; if IgM is detected then an active infection is very likely and if IgG is detected then there is evidence of having had the disease. So.. well, yeah, could be timing, as IgM is not present in significant amounts until mid-stages of infection... Could also vary a lot between individuals: some people have naturally a lower count. Insufficient amount of IgG could just mean that longterm immunity was not developed and/or the infection has not yet run its course... In terms of equipment related causes, the sensitivity of the test could be poor. There could also be issues with sampling and time durations, including any kind of pre-treatment such as incubation that may well be factors in all this.
There are chances that these Rapid test may show negative results when the patient is in the window period of infection.
Further, these rapid tests works on lateral flow immunoassay (LFIA), the major drawback of LFIA is less sensitivity. As WHO guidelines says the rapid test results should be reconfirmed with real-time qPCR.
Mikael Franzen mentioned, the median incubation period for IgM is 4-5 days after onset of symptoms. The timing of testing also matters. Further, the intensity of immune response varies between individuals. These test are best to use after 4 weeks from onset of symptoms, where Antibody (IgG) is at high level. For screening the herd immunity.
For more information please refer below link
https://www.biopanda.co.uk/php/products/rapid/infectious_diseases/covid19.php
Early research indicates that a common test for COVID-19 may produce “false negatives” up to 30 percent of the time.Experts say the inaccuracies are probably caused by the collection of samples, not the actual laboratory testing.
The most common form of test used for COVID-19 is a molecular test known as a reverse transcriptase polymerase chain reaction (RT-PCR) test.The notion is that this is a virus that likes to implant itself on the mucous membranes high up in the back of the throat behind the nose. Swab have to put , not at the front of the nose, but rather far back. We can have a false negative if you have very little virus up there or perhaps the specimen was taken inappropriately or It didn’t get up high enough to actually get to the place where the virus was located.