Swine Flu Test (H1N1)

Swine flu test is performed to distinguish the cause of flu and diagnose H1N1 viral infection when symptoms of flu are present. This test is usually performed within three days of the onset of flu symptoms and provides rapid results in detecting viral antigen in the blood.

The signs and symptoms of flu include:

• Cough
• Sore throat
• High-grade fever with chills
• Sneezing, running nose
• Stuffy nose
• Difficulty in breathing
• Headache
• Body ache (muscle pains)
• Weakness
• Fatigue
• Diarrhoea or vomiting

In severe cases or in hospitalised patients, symptoms of respiratory distress (difficulty in breathing, gasping for breath, etc.) are also seen. Swine flu test is more commonly performed for patients who are:

• Hospitalised
• Have weak immunity (on immune suppressive medicines or suffering from HIV infection etc.)
• At high risk for developing complications
• Aged

A swine flu test is also the first test prescribed for ruling out H1N1 infection during the outbreaks of influenza or respiratory illness.

No special preparations are needed for this test.

It is a simple test that takes less than five minutes. An experienced laboratory specialist collects a blood sample from a vein in your arm by inserting a small needle into the vein. A small quantity of blood is withdrawn into a sterile vial or a test tube. A momentary pricking pain is felt when the needle injects but the procedure itself, is otherwise, risk-free.

Some people may experience light-headedness and bruising at the site of injection. However, at most times, these symptoms disappear quickly. Rarely, an infection may occur at the site of blood withdrawal.

Normal results: An absence of H1N1 is considered normal, which indicates that swine flu is not the reason for the ongoing symptoms.                 

A negative result does not necessarily mean an absence of H1N1 strain; sometimes, it means the presence of an insufficient viral load to be detected or poor specimen collection.

Abnormal results: Presence of  H1N1 antigen in blood indicates an ongoing infection with swine flu virus.

Swine flu test holds more significance for children; elderly; immunocompromised patients; or those with pre-existing lung diseases, such as chronic bronchitis and interstitial lung disease, as they are more prone to complications, such as sepsis, pneumonia, encephalitis etc.

The accuracy of this rapid antigen test is about 70%, which means even if the test is negative, the possibility of having swine flu remains; thus, a thorough clinical history, complete blood count and chest X-ray are mandatory, apart from swine flu antigen test.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. This information is purely from an educational perspective and is in no way a substitute for medical advice from a qualified doctor.