COVID Testing

Options and Accuracy

Wondering if you have been exposed to COVID-19? Curious if that was the reason you were sick in the past few months? If so, maybe you’re considering getting tested. But which test should you get?

There are two main options for testing:
1. Reverse-transcription polymerase chain reaction test, or RT-PCR.
2. Antibody testing

Both tests have their strong points and weak points. The RT-PCR test is best for those that are currently symptomatic. This test uses a swab to collect a sample from the nasopharynx. This is the test the CDC most commonly recommends. But NP swab samples are technically challenging to obtain, and a suboptimal collection may reduce test sensitivity and increase the likelihood of obtaining a false-negative result in a patient with the virus.

The COVID-19 antibody tests look at two forms of antibodies: IgM which is most prominent around the time of symptoms begin to appear and the IgG which occurs about 14 days following symptom onset. Although the IgM antibodies may start to fade as the infection clears, the IgG antibodies will stick around, providing “memory” antibodies against future infections. In studies, antibody tests that detected both IgG and IgM were positive in 90% of symptomatic individuals by days 11-24. 1,2. However, in those with mild symptoms, the level of antibodies formed may be less than in those with significant symptoms.

So what is the sensitivity and specificity of these test and what does sensitivity and specificity mean?

A sensitive test will correctly identify people with the disease. Sensitivity measures correct positive results.

If a test is 90 percent sensitive, it will correctly identify 90 percent of people who are infected. This is called a true positive. However, 10 percent of people who are infected and tested would get a false negative result. This means they have the virus, but the test said they don’t. A specific test will accurately identify people without the disease. Specificity measures correct
negatives.

If a test is 90 percent specific, it will correctly identify 90 percent of people who are not infected. This is called a true negative. However, 10 percent of people who are not infected will test positive for the virus. These 10% are said to be false positive.

To reiterate: Sensitivity measures positive accuracy; specificity measures negative accuracy. After doing some research, we have decided to offer antibody testing to our clients. We have teamed up with one of our labs and to provide COVID-19 antibody testing which is 97.5% specificity and 95.6% sensitivity. Although there is no perfect test, we are offering this antibody test at Essex Medspa as we feel it is the better option, with less variability due to timing of infection and adequate sample collection. If you are interested please call to schedule an appointment.

COVID Testing

Options and Accuracy

Wondering if you have been exposed to COVID-19? Curious if that was the reason you were sick in the past few months? If so, maybe your considering getting tested. But which test should you get?

There are two main options for testing:
1. Reverse-transcription polymerase chain reaction test, or RT-PCR. 
2. Antibody testing

Both tests have their strong points and weak points. The RT-PCR test is best for those that are currently symptomatic. This test uses a swab to collect a sample from the nasopharynx. This is the test the CDC most commonly recommends. But NP swab samples are technically challenging to obtain, and a suboptimal collection may reduce test sensitivity and increase the likelihood of obtaining a false-negative result in a patient with the virus. The COVID-19 antibody tests look at two forms of antibodies: IgM which is most prominent around the time of symptoms begin to appear and the IgG which occurs about 14 days following symptom
onset. Although the IgM antibodies may start to fade as the infection clears, the IgG antibodies will stick around, providing “memory” antibodies against future infections. In studies, antibody tests that detected both IgG and IgM were positive in 90% of symptomatic individuals by days 11-24. 1,2. However, in those with mild symptoms, the level of antibodies formed may be less
than in those with significant symptoms.

So what is the sensitivity and specificity of these tests and what does sensitivity and specificity mean?

A sensitive test will correctly identify people with the disease. Sensitivity measures correct positive results.

If a test is 90 percent sensitive, it will correctly identify 90 percent of people who are infected. This is called a true positive. However, 10 percent of people who are infected and tested would get a false negative result. This means they have the virus, but the test said they didn’t. A specific test will accurately identify people without the disease. Specificity measures correct
negatives.

 

If a test is 90 percent specific, it will correctly identify 90 percent of people who are not infected. This is called a true negative. However, 10 percent of people who are not infected will test positive for the virus. These 10% are said to be false positive. To reiterate: Sensitivity measures positive accuracy; specificity measures negative accuracy. After doing some research, we have decided to offer antibody testing to our clients. We have teamed up with one of our labs and to provide COVID-19 antibody testing which is 97.5% specificity and 95.6% sensitivity. Although there is no perfect test, we are offering this antibody test at Essex Medspa as we feel it is the better option, with less variability due to the timing of infection and adequate sample collection. If you are interested please call to schedule an appointment.