In the case of only a short-term cough (up to 8 weeks) in the context of an acute inflammation of the upper respiratory tract, laboratory diagnostics are usually not necessary. If special circumstances are present that are not typical of an acute trivial respiratory tract infection, diagnostics for acute cough should be initiated immediately. See Cough/Symptomatic Complaints/Red flags.
2nd order laboratory parameters – depending on the results of the history, physical examination, and obligatory laboratory parameters – for differential diagnostic clarification.
- Small blood count
- Differential blood count – if infection or immunodeficiency is suspected.
- Inflammatory parameters – CRP (C-reactive protein) or PCT (procalcitonin).
- Bacteriologic examination of sputum, tracheal secretions/pharyngeal swab (nasopharyngeal swab if sputum cannot be produced; bronchial lavage (flushing of bronchi for diagnostic purposes) – if microbial cause is suspectedNote: Send only macroscopically purulent sputum specimens or other deep respiratory materials. Sputum should be obtained by vigorous coughing – preferably in the morning.
- Bordetella pertussis antibodies (IgA, Ig G, IgM) – if pertussis (whooping cough) is suspected.
- IgG, IgA, IgM – for suspected humoral immunodeficiency.
- Ig E – in suspected atopic diathesis, immunodeficiency, allergic bronchopulmonary aspergillosis (ABPA).
- Specific IgE – in suspected cases of sensitization.
- Measles virus antibodies (IgG, IgM) – if morbilli (measles) is suspected.
- Allergy diagnostics
- Sputum cytology – if bronchial carcinoma (lung cancer) is suspected.
- NT-proBNP (N-terminal pro brain natriuretic peptide) – in suspected heart failure.
- Biopsy (tissue sample) – for histological/fine tissue examination.
- Molecular genetic testing – for suspected cystic fibrosis.
