COVID Test Basics

How COVID testing works and what it means for you

a plant with coins in a glass

There are two types of tests

The nucleic acid amplification test (NAAT) or viral “Swab test”, and the immunoglobulin, antibody test or “Blood test.” These are used for very distinct circumstances.

The swab test

If you have signs of an active infection, the test you get is the Swab Test. There are now designated drive through testing sites throughout the city. Many clinics, including myself, have deliberately decided to not perform swab tests in office to minimize risk to other patients who need primary care services. Also, there are now many free drive through testing locations throughout San Antonio.

The antibody test

The second test is the antibody test. An antibody is your immune response so this test will potentially show if you had the infection in the past. There are a couple key things to know about this testing. After reading the following, you may be asking yourself, “Why then would I get the antibody test?” That is a great question and currently I have not pursued this test myself or recommended it to my friends, family, or patients who have not had a COVID-like illness.

  • “It cannot be assumed that presence of antibodies confers protection from reinfection until durability and duration of immunity is established”
  • “Asymptomatic persons who test positive without recent history of compatible illness have low likelihood of active infection and should follow recommendations to prevent infection”
  • “No change to clinical practice or use of personal protective equipment (PPE) should be made…” for people who test positive for antibodies
  • “Here in San Antonio it’s very likely that a positive test is no better than a coin toss.” The reason for this takes time to explain but it has to do with statistics and the terms: pretest probability and test specificity/sensitivity.

Testing in San Antonio, Texas

So the main point: if you have any symptoms, get the swab test. Otherwise, I am still not convinced that the antibody test has much utility in San Antonio but should be looked at on a case by case basis, such as before a surgery. You can find Texas COVID-19 Swab Test Collection Sites here.

New data on COVID 19 comes out daily and I have several clients who work in healthcare, so if you have any information that you would like to add, please send me an email and link to your source:

Sources:,, San Antonio Current. Dr Ruth Berggren with UT Health, Drs. Carlos Cordon-Cardo and Adolfo Garcia-Sastre, Icahn School of Medicine.