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  5. Does the flu show up in blood work?

Does the flu show up in blood work?

Yes, when we take samples from a vein and perform serology tests, the flu shows up. There are many tests performed to diagnose Influenza or flu in various ways, i.e., by taking samples from the respiratory tract or by taking a blood sample.

How?

When we take blood samples, flu shows by the formation of antibodies in the blood, but the appearance of antibodies takes time, so that is why it does not help so much in the diagnosis of flu, but it is used to check the prior infection.  

Influenza tests: 

Serology tests measure antibodies to the influenza virus in a blood sample or patient’s serum. Antibodies are developed as part of the immune reaction in response to viral infection. Time is taken for antibodies to form, so serology tests are used to identify a prior infection.

What is Influenza?

Influenza is commonly knowns as flu. It is a viral disease that affects the upper or lower respiratory tract i.e., nose, throat, and sometimes lungs. It is caused by influenza viruses and is a mild to severe illness.

Types of Influenza:

  • Influenza A
  • Influenza B
  • Influenza C 
  • Influenza D 

In the United States, every winter season, Human Influenza A and B viruses cause seasonal epidemics of disease, which is called flu season.

Symptoms: 

  • Runny nose
  • Sore throat
  • Dry, persistent cough
  • Fever and chills
  • Sneezing
  • Feeling tired and weak
  • Headache
  • body aches etc.

How to diagnose Influenza?

Most diagnoses of Influenza are made on clinical grounds; laboratory tests are available. Serological tests (Detection of antibodies in the patients’ serum) include:

  • Influenza A and B Antibodies Test, Quantitative
  • Cold Agglutinin Titer Blood Test, Quantitative

Influenza A and B Antibodies Test, Quantitative:

This test is designed to diagnose the two influenza viruses i.e., Influenza A virus (which causes a worldwide pandemic of Influenza) and influenza B (which causes significant influenza outbreaks) viruses. It is a serological test.

Test details:

  • It is used to detect antibodies of influenza A and B.
  • The specimen is blood serum.
  • The volume of the specimen should be 1ml and a minimum of 0.5ml.
  • The container that contains the serum is the Red-top tube or gel-barrier tube.
  • The specimen should be refrigerated for storage.
  • The methodology is complement fixation.
  • The turnaround time is about 4-5 days.

Note: This test is not used to detect the H1N1 Influenza A virus.

Reference rages:

  • Influenza type A antibody is <1:8 titer
  • Influenza type B antibody is <1:8 titer

(titer is the measure of the level of the antibodies in the blood sample)

Cold Agglutinin Titer Blood Test, Quantitative:

A Cold Agglutinin Titer Blood Test is designed to diagnose Influenza as well as pneumonia, gangrene, hemolytic anemia, some other viral and infectious diseases, etc. It is a serological test.

Test details:

  • It is used to detect the presence of cold agglutinins. 
  • Specimen is blood serum.
  • The volume of the specimen should be 1ml and a minimum of 0.5ml.
  • Container that contains the serum is a Red-top tube or gel-barrier tube.
  • Collect the blood sample, transport it immediately to the laboratory and incubate it to clot. After clotting, separate the serum from the red blood cells.
  • Store the separated serum in the refrigerator.
  • Refrigeration of serum before separation from red blood cells causes rejection. 
  • Methodology is hemagglutination.
  • Turnaround time is about 4 to 5 days.

Reference range:

  • Negative: <1:32 

Reliability and interpretation of tests:

The reliability of diagnostics tests for Influenza depends on the conditions under which they are used. Proper interpretation of test results is the most important step for accurate clinical management of the patients who are suspected of Influenza. Having basic knowledge avoids false positive and negative results.

Conclusion:

By performing serology tests ,flu shows up. Influenza (flu) is a viral disease caused by an influenza virus. This disease can be worse with time if not diagnosed and treated earlier. There are many diagnostic tests for Influenza. Some basic serologic tests are explained above i.e., Influenza A and B Antibodies Test, Cold Agglutinin Titer Blood Test.

References: