Weak streak in antigen test: does that mean you got infected?

Home antigen tests have become an integral part of parents’ routine lives, at least for those of them who do make sure to test their children through them. According to the outline that began earlier this month, all children in education up to the age of 18 should undergo a home corona test twice a week.There are quite a few times when the bandwidth that heralds a positive answer can be darker or weaker. What does this mean in terms of the chance that we are indeed verified and why is this happening? “First, it’s important to make clear: every line is a line, so it should not be underestimated,” says Dr. Dudi Steiner, an immunologist, a member of the “Madat” association and former developer of antigen tests. “It is likely that the person whose examination showed two stripes is positive for Corona.”

PCR And antigen – recognize the differences

First, a brief explanation of the difference between a PCR test and an antigen: “A PCR test is actually an example of a short section of the genetic load of the virus and this section is ‘amplified’ in the laboratory. In simple words – billions of copies of it are produced. The virus-specific allows us to detect the virus.

“On the other hand, in the antigen test we do not have such an ‘amplification’ ability – what we test is what is there. The antigen test actually checks for the presence of a protein of the virus. Up to a certain threshold, it is unable to detect the protein, even if it is low. We could increase the amount as in PCR, the sensitivity of the test would increase, but it was a longer and more cumbersome test. ”

How does this relate to the bandwidth of the test? “As mentioned, the antigen test can only detect a protein that is present in a certain amount. Therefore, when it comes to very early stages of infection, the amount is still not large enough and therefore the chance of detecting the virus is small. The protein and with it the strength of the line, which becomes strong and clear, and vice versa – the more the virus is detected at the margins of the time frame of onset of the disease (at the beginning or end), the weaker the line appears.

“In other words – if you have identified a weak line, you can draw two conclusions from this: the first – that you are infected with corona; and the second – that you are at the beginning of the disease or at the end.”

 

Dr. Steiner notes that because of the large difference between the PCR test and the antigen, the PCR test Can detect the virus at an earlier stage than can be detected by antigen testing.

“For example – if someone received a PCR answer that means ‘weak positive’, in an antigen test he still came out negative, and even a weak line will not be shown. It necessarily indicates a negative answer, hence the importance of performing this test every two days from the moment of exposure to a verified patient. ”