Parainfluenza Tests

What is a parainfluenza test?

A parainfluenza test checks a fluid sample from your nose or lungs for the four types of parainfluenza viruses (also called human parainfluenza viruses, or HPIVs). These viruses are a common cause of respiratory (breathing) illnesses, especially in spring, summer, and fall.

Parainfluenza viruses aren't the same as flu (influenza) viruses.

However, like the flu, parainfluenza spreads easily from person to person. The most common ways for the virus to spread are:

• Through the air, usually by a person with the infection who coughs or sneezes
• Through touch, usually by touching a surface that has a parainfluenza virus on it, and then touching your mouth, nose, or eyes

The most common way to check for parainfluenza viruses is with a PCR (polymerase chain reaction) test. This is a kind of molecular test that can find very small amounts of genetic material from parainfluenza viruses in the fluid sample from your nose or lungs.

Other tests for parainfluenza virus are used less often. This is because:

• Rapid antigen tests are less accurate and must be done within a week after symptoms begin
• Viral culture tests take much longer than other tests
• Blood tests are mainly used for research

In some cases, parainfluenza testing may be done as part of a respiratory pathogens panel. This is a group of tests that checks for several viruses and bacteria that cause respiratory illnesses.

Other names: human parainfluenza virus test; HPIV test; HPIV-1 test; HPIV-2 test, HPIV-3 test; paraflu 1-4 PCR; parainfluenza 1-4 by PCR; parainfluenza PCR panel; PIV

What is it used for?

Parainfluenza tests are used to see if one of the four parainfluenza viruses is causing an illness that affects your nose, throat, lungs, and bronchial tubes (the airways that carry air to your lungs).

These viruses commonly cause respiratory illnesses such as croup in babies and younger children, but anyone can get sick from them. If you're healthy and have a parainfluenza illness, you'll probably have mild symptoms like those of a common cold, such as a runny nose or cough. You'll also usually get better on your own.

However, if you have a weakened immune system or are an older adult, you're more likely to develop more serious illness from parainfluenza infections. These illnesses include bronchitis and pneumonia.

You can have parainfluenza illnesses more than once in your life.

Why do I need a parainfluenza test?

You or your child may need a parainfluenza test if either of you have:

• Symptoms of a respiratory illness and
• A higher risk of getting seriously sick from a parainfluenza illness

Symptoms of parainfluenza and other respiratory illnesses may include:

• Fever
• Sore throat
• Wheezing
• A long-lasting cough that may sound like barking (croup)
• Shortness of breath
• Too much mucus in the lungs or airways (congestion)
• Rapid breathing

You may be at higher risk of getting seriously sick from a parainfluenza illness if you:

• Have a condition that affects your immune system, such as HIV or certain blood cancers
• Have had blood stem cell, bone marrow, or organ transplants
• Have a heart disorder
• Have a lung disorder such as asthma
• Are in the hospital with community-acquired pneumonia (pneumonia that you catch during your usual daily life, not from spending time in a hospital or other health facility)
• Are an older adult

Young children and infants are also at higher risk of getting seriously sick from a parainfluenza illness.

If you have symptoms of a respiratory illness but aren't at high risk of getting seriously sick, you probably won't need testing. That's because in healthy people parainfluenza illnesses usually get better on their own.

If you have symptoms of a respiratory illness and do have a high risk of getting seriously sick, treatment decisions will depend on whether you have a viral or bacterial infection. Because of this, your provider may order a respiratory pathogens panel, which can check for both infection types.

What happens during a parainfluenza test?

Tests to diagnose parainfluenza viruses are usually done on a sample of fluid from your lungs or airways (such as your nose, mouth, or throat).

A sample from your nose may be used if you've had symptoms between 3 and 7 days. Most tests are done with this type of sample. The sample may be collected using one of these methods:

• Nasal aspirate or wash. To do a nasal aspirate, a health care professional will insert a saline solution (salt water) into your nose and remove it with gentle suction.
• Swab test. A health care professional will use a special swab to take a sample from either:
  • Deep in the back of your nose
  • An inch deep inside both of your nostrils and from your throat using a separate swab inserted through your mouth

A sample from your airways or lungs may be used at any time during your illness. The fluid may be collected with one of these methods:

• Sputum test. Sputum is a thick mucus from the lungs. It is different from saliva (spit). To get a sample, you will be asked to cough up sputum into a special container.
• Bronchoalveolar lavage (BAL). A BAL collects a sample of fluid from your lung. This type of sample is usually used only if you are very ill. A doctor will insert a narrow, flexible tube (a bronchoscope) down your throat and into your lung. A small amount of salt water will be injected through the tube into your lung and then suctioned out. Numbing medicine will be used in your mouth and throat. You may also have medicine to help you relax.

Will I need to do anything to prepare for the test?

If you have a BAL, you may need to fast (not eat or drink) for several hours before the test. You should plan to have someone take you home because you may feel sleepy if you are given medicine to relax.

You don't need any special preparations for other parainfluenza tests.

Are there any risks to the test?

There is very little risk to having a parainfluenza test:

• A nasal aspirate or wash may feel uncomfortable. These effects are temporary.
• Nasal and throat swabs may cause a brief gagging feeling.
• A BAL may cause a sore throat for a few days. Serious problems are rare. They include bleeding in the airways, infection, or a partly collapsed lung.

What do the results mean?

A negative result means that no signs of parainfluenza viruses were found in your sample. Another illness is probably causing your symptoms. But a negative test result doesn't rule out a parainfluenza illness. It's possible that there was too little virus in your sample for the test to find.

A positive result means that you likely have a parainfluenza infection. But it's possible for a PCR test to show signs of a virus even though you don't have enough virus in your body to make you sick.

If you had a respiratory pathogens panel, your results may state which viruses or bacteria were found. If the test found evidence of a bacterial infection, your provider may treat it with antibiotics. There is no cure for parainfluenza viruses, but you can do things to help your symptoms. Talk with your provider about what your test results mean and about what steps you can take to help your symptoms if you have a parainfluenza infection.

Learn more about laboratory tests, reference ranges, and understanding results.