Influenza (Flu): Test and Diagnosis

In most cases, physical examination and precise information about the onset of the disease and symptoms are sufficient for the physician.2nd order laboratory parameters – depending on the results of the medical history, physical examination, etc. – for differential diagnostic clarification

• Antibodies against influenza viruses (A and B) – antigen detection: respiratory tract secretions (sputum, bronchial secretions, pharyngeal lavage, tracheal secretions).
• In severe courses or complications, the virus should be detected by laboratory diagnosis. This is done by taking pharyngeal lavage fluid within the first two days of illness. For rapid diagnosis, direct detection of viral antigens is performed by ELISA or rapid test. Further typing and genome detection is performed in specialized laboratories (influenza A seasonal (H3N2) and A (H1N1) pdm09; influenza B).
• If new influenza (swine influenza) or avian influenza (avian influenza; H5N1) is suspected, a nasal/pharyngeal swab should be performed; PCR for nucleic acid detection (specific RT-PCR) is performed from these.Laboratory diagnosis must be performed by at least one of the following three methods:
  • Nucleic acid detection (specific RT-PCR).
  • Serological differentiation or molecular typing (molecular genetic testing).
  • Fourfold increase in titer of the specific influenza antibody.

The flu is subject to mandatory reporting. That is, as soon as the laboratory results determine that it is the influenza, the doctor gives notification of this to the relevant health department. This is to prevent further spread of the disease.

Vaccination status – checking vaccination titers