Parainfluenza Tests
Parainfluenza tests identify the presence of human parainfluenza viruses (HPIVs), which are common causes of respiratory illnesses like the common cold, croup, and pneumonia.
What is a parainfluenza test?
Parainfluenza viruses are a group of four viruses that cause respiratory illnesses affecting the nose, throat, lungs, and bronchial tubes. These viruses are distinct from the flu (influenza) and are most common in the U.S. during the spring, summer, and fall.
Most healthy people recover from parainfluenza on their own. However, older adults and those with weakened immune systems are at risk for serious conditions like croup, bronchitis, and pneumonia. The most common diagnostic method is a molecular test, such as a PCR (polymerase chain reaction) test, which detects the virus's genetic material.
Why do I need a parainfluenza test?
Testing is generally reserved for individuals at high risk of serious illness, including those with:
- Weakened immune systems (e.g., transplant recipients, blood cancer patients, or those with HIV).
- Heart or lung disorders.
- Community-acquired pneumonia.
- Advanced age.
Symptoms that may prompt testing include fever, sore throat, wheezing, a persistent "barking" cough, shortness of breath, congestion, and rapid breathing.
What happens during a parainfluenza test?
Samples are typically collected from the nose or chest:
- Nasal aspirate or wash: Saline solution is inserted into the nose and removed via gentle suction.
- Swab test: A swab is used to collect fluid from deep in the nose or from the nostrils and throat.
- Sputum test: You are asked to cough up thick mucus from the lungs into a container.
- Bronchoalveolar lavage (BAL): A doctor inserts a bronchoscope (a thin, flexible tube) into the lung to collect fluid. This is typically reserved for very ill patients.
Preparation and Risks
No special preparation is needed for most tests. If you are undergoing a BAL, you may need to fast for several hours beforehand and arrange for someone to drive you home due to the use of sedatives. Risks are minimal, though nasal procedures may be uncomfortable, and a BAL can cause a temporary sore throat or, rarely, more serious complications like bleeding or a partially collapsed lung.
What do the results mean?
- Negative result: No signs of the virus were found. Your symptoms may be caused by another illness, though a negative result does not definitively rule out parainfluenza if the viral load in the sample was too low.
- Positive result: You likely have a parainfluenza infection. Note that PCR tests are highly sensitive and may detect viral material even if the amount is insufficient to cause active illness.