Flu Diagnosis and Diagnostic Tests Are Important
Influenza Rapid and Standard Tests and the Signs and Symptoms of Flu
May 11, 2009
During epidemics or pandemics there are many patients and problems. It is important to treat each correctly-diagnosed infectious disease in an appropriate manner. To sort out what is happening during an infectious disease outbreak such as flu, diagnostic tests sometimes are used. These tests fall into two categories: screening tests and definitive tests.
Signs, Symptoms and Basic Therapy of Viral Respiratory Diseases
During an epidemic, multiple viruses and bacteria may be circulating in the diseased population. There are rhinoviruses, adenoviruses, and influenza among the culprits that make people sick. The goal is simple: treat the disease in the right way to help patients recover and get back to normal. For upper, respiratory infections, the signs and symptoms may be very similar, even with different viruses, or some bacteria:
- fever
- cough
- throat pain
- headache
- body ache.
Most viral respiratory treatments are similar: adequate fluids, acetaminophen, cough medicines as needed, and, of course, bed rest. Occasionally, influenza drugs are used. Regardless, normal, host immune system strengthening and recovery is always important.
Flu Diagnostic Testing Helps Define the Disease and the Viruses
In suspected flu epidemics it is desirable to answer these questions:
- Is this influenza?
- If so,what strain?
- Is this an older, known strain, or is it new?
New vaccines may need to be prepared if there is a new strain. Often, knowing what is happening is important. That is why screening and definitive tests are sometimes used.
Flu Rapid Diagnostic Tests Are Helpful Sometimes
Typical, viral upper respiratory tract infectious diseases are treated similarly as indicated above. There are occasions when screening tests are done to determine what is happening. Nursing home and military settings are of particular interest because of the large number and significance of the people involved. There are about a dozen, rapid diagnostic screen tests for influenza. Both the US Centres for Disease Control (Rapid Diagnostic Tests For Influenza, 2009) and the US Food and Drug Administration (Cautions in Using Diagnostic Tests for Rapid Influenza Diagnosis, 2009) recommend caution and wisdom in the use of tests. A summary and analysis follows:
- nasal, nasopharyngeal or throat swabs are typically used.
- results are obtained typically in about 15 minutes or less.
- flu rapid diagnostic tests have an overall have a 50-70 % sensitivity and reliability level compared to standard rigorous RT-PCR and culture lab tests.
- there will be some false positives and negatives.
- rapid tests define only type A or B types, not the specific subtype or strain, such as H1N1, H5N1, H3N2.
Epidemic Strain Identification and Characterization
The following tests help define the actual types and subtypes or strains involved in 2-4 hrs:
- RT-PCR, or reverse transcriptase polymerase chain reaction, (types and subtypes).
- IFA, Indirect Fluorescent Antibody staining, (types and HA subtypes).
Flu and other viral epidemics , therefore, can be defined and followed. This is important when one considers the effects that epidemics have on businesses, commerce, education, recreation and just ordinary living. A better understanding of the nature of epidemics and pandemics, and the available epidemiological tools, is important for all.
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