How Coronavirus (COVID-19) Is Diagnosed

As 2020 rages on, the novel COVID-19 has spread worldwide, resulting in growing numbers of infected individuals and mortality throughout the U.S.

Since March, COVID-19 testing availability in the U.S. has increased rapidly, and wait times for results have shortened. Now that researchers have discovered a wide asymptomatic spread of the virus, testing recommendations have vastly changed as well.

Known exposure to someone who has been infected with the virus, experiencing COVID-19 symptoms, or even attending large gatherings may raise concerns and prompt diagnostic testing. Because the virus has spread across the entire U.S., it is likely that a person could have been exposed unknowingly, so monitoring exposure and regular testing is now paramount.

Diagnosis of COVID-19 involves molecular or antigen tests. Once someone has been diagnosed with COVID-19, additional diagnostic tests may be done to determine the severity of the infection.

Who Can Get Tested?

The Centers for Disease Control and Prevention (CDC) continues to issue evolving recommendations for getting tested.

Situations in which they recommend you seek a COVID-19 test include:

• If you have symptoms of COVID-19
• If you have been in close contact (less than 6 feet for a total of 15 minutes or more) with documented SARS-CoV-2 infection and do not have symptoms
• If you are in a high SARS-CoV-2 transmission zone and attended a public or private gathering of more than 10 people (without universal mask-wearing and/or physical distancing)
• If you work in a nursing home
• If you live in or receive care in a nursing home
• If you are a critical infrastructure worker, healthcare worker, or first responder

The CDC adds that there may be other situations in which public health officials or healthcare providers may advise specific people to get tested. If specifically recommended by an official or provider you should get tested. Situations like this can include:

• If you're about to be admitted to the hospital or preparing for a procedure
• If there is significant spread of the virus in your community, your public health department may request significant numbers of asymptomatic “healthy people” to be tested in order to help stop the spread of the virus

Steps to Getting Tested

COVID-19 testing is now much more widely available across the U.S. than at the start of the pandemic. Now you can find testing available at most local pharmacies like Walgreens and CVS, as well as at your doctor's office, or local testing sites.

The CDC recommends contacting your healthcare provider before getting tested. But you can also find up to date information about local and state testing by visiting your state or local health department’s website. Several companies are now offering at-home COVID-19 tests with quick results as well.

If you think you may be sick but haven't talked to a healthcare provider yet, use our printable Doctor Discussion Guide below to help prepare you for your appointment.

Coronavirus (COVID-19) Doctor Discussion Guide

Get our printable guide for your next doctor's appointment to help you ask the right questions.

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Types of Tests

In the U.S., the CDC was the first to offer a COVID-19 test, with private companies soon following suit. These tests can be used to diagnose an infection because they detect the genetic material of the virus itself. There are currently two types of COVID-19 tests that can detect an active infection: diagnostic molecular tests and diagnostic antigen tests. Antibody tests are also available but are only used to determine if you previously had the disease. The FDA has granted Emergency Use Authorization (EUA) to many COVID-19 diagnostic tests. The full list is available on the FDA website.

Diagnostic Molecular Tests

Diagnostic molecular tests, or RT-PCR are the most reliable option available for diagnosing COVID-19. A molecular test can be done on samples from nasal or throat swabs, as well as saliva samples. These tests are performed using a technique known as Polymerase Chain Reaction (PCR), which works by rapidly making millions to billions of copies of viral-related DNA. It can detect even small amounts of this genetic material in the collected sample. Molecular tests are extremely sensitive, so a positive test result is almost never wrong in detecting COVID-19.

Since these types of tests are typically performed in specific labs, getting results back can be a slow process, taking anywhere from 2 days to over a week, depending on cases in your area.

Diagnostic Antigen Tests

Antigen COVID-19 tests, or rapid tests, typically provide results faster than a molecular test, but they also have a higher chance of missing an active infection. They can provide results within minutes, however, compared to a molecular test, more of the virus needs to be present in order to test positive. Sometimes, if an antigen test comes back with a negative result, your healthcare provider may ask you to complete a molecular test to confirm the result.

Antibody Tests

An antibody test is used to look for the body's immune response to SARS-CoV-2. While the blood test typically provides quick results, it is only good for determining if you had the disease not if you have a current infection. Antibody tests should not be used to diagnose an active infection. Experts currently do not know if antibodies give you protective immunity against the virus, so you should not use antibody test results to determine if you have immunity to the virus.

You should not use antibody test results as an indication to stop taking protective measures like social distancing and wearing masks.

Results

If your test is positive: This means that you have been infected by the virus. But it doesn’t necessarily mean that COVID-19 is the only cause of your illness. A co-infection with another virus or bacteria could be causing your symptoms as well.

If your test negative: Other factors are important to help confirm you are truly free of COVID-19, such as your symptom history and clinical examination. You may have been infected by the virus, but its presence could be undetected in your sample, or your test results gave you a false negative. 

Self-Checks

Your own assessment of your risk of infection involves staying up to date on your exposure risk. If you have been to places where the illness has been identified or if you have interacted with people who were infected or exposed to the virus, you could be at risk and should seek out a test.

Again, because the virus is spreading rapidly throughout the United States and the whole world, you could have been exposed without knowing it.

You should monitor your own health for signs of COVID-19 infection. Things to look out for include:

• Fever or chills
• Cough
• Shortness of breath or difficulty breathing
• Fatigue
• Muscle or body aches
• Headache
• New loss of taste or smell
• Sore throat
• Congestion or runny nose
• Nausea or vomiting
• Diarrhea

Keep in mind that some of these symptoms are common and can occur with sinusitis, pneumonia, bronchitis, or any viral or bacterial respiratory infection, including the flu.

Because severe cases of COVID-19 infection can cause pneumonia, acute respiratory distress syndrome, kidney failure, and even death, it is important that you are especially vigilant about any rapid decline in your health or sudden worsening of symptoms. 

The CDC also recommends looking for potential emergency warning signs that require immediate medical attention, including:

• Trouble breathing
• Persistent pain or pressure in the chest
• New confusion
• Inability to wake or stay awake
• Bluish lips or face

Physical Examination

When you go to see your doctor, they will perform a medical history and a physical examination. Your examination will include assessing your breathing. The doctor will also check your temperature for a fever.

Chest Sounds

Your exam will include evaluation of your chest sounds. Lung infections and lung disease can cause characteristic changes in chest sounds such as crackling or wheezing.

Your doctor can hear these sounds with a stethoscope. Keep in mind that the presence or absence of abnormal breath sounds does not confirm or rule out an infection with COVID-19.

Evaluation of Respiratory Distress

Your doctor will check for respiratory distress and signs of dyspnea (shortness of breath). Advanced lung infections can make you short of breath and may make it difficult to breathe.

If you are struggling to breathe, your doctor may notice that you are using accessory muscles to help you as you inhale. This is a sign of advanced lung disease or a severe infection.

Tachypnea

Sometimes lung problems can cause you to breathe rapidly (tachypnea), which is a sign of severe lung disease. A rate above 12 to 20 breaths per minute is considered high for an adult.

Labs and Tests

Depending on your symptoms, additional tests may be needed to evaluate possible complications of your infection. Keep in mind that these tests aren’t used to diagnose COVID-19, but may be needed if the effects become severe.

• Complete blood count (CBC): Measures your white blood cells (WBCs) and red blood cells (RBCs)
• Pulse oximeter: A non-invasive test that can give your doctors a general idea of your oxygen level
• Arterial blood gas (ABG): A blood test that can show more precise measures than a pulse oximeter
• Electrolyte levels: Your doctor may order this test if you are showing signs of severe illness

Imaging 

Chest imaging studies, including chest X-ray and chest computerized tomography (CT) may show changes with COVID-19 infection, but these changes are not specifically diagnostic of this infection, and can be present with other lung conditions like pneumonia and bronchitis.

Both sides of the lungs are usually involved about equally. With COVID-19 infection, the lungs often have the appearance of lung inflammation that is usually described as ground-glass opacity on a CT because it looks like the lungs are obscured by ground glass. This is a relatively common pattern seen with other lung infections too.

Differential Diagnosis

One of the challenges when it comes to COVID-19 infection is that it presents in a way that is very similar to other viral and bacterial respiratory infections, including colds, the flu, and strep throat. The symptoms don’t necessarily distinguish the illnesses from each other.

Your doctor may order a flu test or a test for strep throat if you seem likely to have these other illnesses based on your exposures and risk factors.

A Word From Verywell

While the eventual impact of COVID-19 isn’t certain, testing can help by getting prompt medical care for those who are at high risk of developing a fatal infection. If you have lung disease, heart disease, or a weakened immune system, an infection with COVID-19 is especially dangerous for you.

However, the infection can be severe even if you are otherwise healthy. Keep in mind that you may still be at risk of newly contracting the infection even after you have a negative test that doesn’t show evidence of the virus.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.