The Two Coronavirus Tests You Need to Know About

Understanding the key differences between diagnostic and antibody tests

In the early stages of the Covid-19 pandemic, much of the conversation focused on diagnostic testing, a crucial tool for identifying people who could transmit the disease. Diagnostic testing is still an enormous priority now, but more recently, a second type of testing has emerged on the scene: antibody testing, a very different tool that provides different information. It can be confusing to keep track of the two, so here’s a brief guide to what makes each important.

Diagnostic tests are used to diagnose people who currently have Covid-19 — and they’re especially important because many people who have the disease show no symptoms. The diagnostic test that the United States currently relies on involves taking a nasal swab from a person and then searching for traces of the virus in that sample using a laboratory technique called polymerase chain reaction, or PCR. This is the gold standard for diagnostic testing, but it takes a long time to complete — about six to eight hours. As a result, there’s a growing backlog of people waiting to get their results.

Diagnostic testing across the United States continues to fall short of what’s needed to effectively track the spread of Covid-19. According to the Covid Tracking Project, roughly 150,000 people have been tested each day over the past week. Recent research from Harvard University suggests that 500,000 to 700,000…