Laboratory parameters of the 1st order – obligatory laboratory tests.
- Blood count – frequently leukocytosis (proliferation of white blood cells) with leftward shift, i.e., shift in granulocytes in favor of younger precursors (e.g., rod-nucleated granulocytes; possibly toxic granulations)
- ESR (blood sedimentation rate) ↑↑↑ or CRP (C-reactive protein) ↑↑↑ [CRP threshold: 30 mg/l; mean: 97] or procalcitonin ↑↑↑ (procalcitonin increases within a few hours (2-3 h) and reaches its maximum after only 24 hours) [neither leukocyte count nor CRP can confirm the diagnosis of pneumonia; procalcitonin can possibly shorten or avoid antibiotic therapy]Note: patients (here: adults) without elevated PCT concentrations usually do not have bacterial infections either; serum PCT concentrations: viral infections had a median of 0.09 ng/ml, infections with atypical bacteria (chlamydia, rickettsia, mycoplasma, legionella) had 0.20 ng/ml, and typical bacterial pneumonia had a median of 2.5 ng/ml. A European study of children and community-acquired pneumonia was able to confirm that a low value was associated with a reduced probability of bacterial-induced community-acquired pneumonia: sensitivity was 86% (percentage of ill patients in whom the disease is detected by the use of the procedure, that is, a positive finding occurs), but the specificity of the test was very unsatisfactory at 45% (probability that actually healthy people who do not have the disease in question are also detected as healthy in the test).
- BNP (brain natriuretic peptide) – prognostic marker; this shows the 30-day mortality risk of patients with community-acquired pneumonia (CAP) [BNP level ≥ 224.1 pg/ml; at this threshold: sensitivity 58.8% (percentage of diseased patients in whom the disease is detected by the use of the test, ie. i.e., a positive test result occurs) and specificity 80.8% (probability that actually healthy individuals who do not have the disease in question are also detected as healthy by the test). ]
Laboratory parameters 2nd order – depending on the results of the medical history, physical examination, etc. – for differential diagnostic clarification.
- Blood gas analysis (BGA)
- Detection of the pathogen from sputum, pleural exudate, bronchial secretions, or lung biopsyIndications for sputum diagnostics in community-acquired pneumonia (AEP; English CAP = community acquired pneumonia): severe course of disease with hospitalization, immunocompromised patients, comorbidities (concomitant diseases), relapse (recurrence of the disease), antibiotic pretreatment, etc. Note: in CAP, sputum tests have low sensitivity (percentage of diseased patients in whom the disease is detected by the use of the test, i.e., a positive test result occurs) and specificity (probability that actually healthy individuals who do not have the disease in question are also detected as healthy in the test); furthermore, the pathogens in question are known
- In case of atypical pneumonia (Chlamydia (Chlamydophila pneumoniae: ornithosis), Mycoplasma (Mycoplasma pneumoniae), Legionella, Pneumocystis carinii, viruses (eg, influenza viruses; parainfluenza, enteroviruses, human coronaviruses), rickettsiae).
- Bacteriology (cultural): respiratory tract secretions (sputum, bronchoalveolar lavage) for pathogens and resistance (also Legionella, Mycoplasma Ag).
- Serology: detection of AK against Chlamydia, Coxiella burnetti, Legionella, Mycoplasma, Pneumocystis carinii.
- Quantitative PCR and immunofluorescence: Detection of Pneumocystis carinii
- Blood cultures (aerobic and anaerobic blood cultures; 2 times 2 or better 3 times 2 blood cultures).
Pneumonia can be caused by the following pathogens:
- Atypical pathogens – Chlamydia, Legionella, Mycoplasma, Rickettsia and others lead to atypical pneumonia.
- Bacteria – Branhamella catarrhalis, Chlamydia pneumoniae, Haemophilus influenzae, Klebsiella pneumoniae* , Legionella, pneumococci, staphylococci, Pseudomonas aeruginosa.
- Viruses – adenoviruses, cytomegalovirus, enteroviruses, Hanta virus, influenza A-B virus, measles virus, parainfluenza virus, respiratory syncytial virus (RSV), varicella zoster virus.
- Fungi – Aspergillus, Blastomyces spp, Candida, Coccidioides, Histoplasma.
- Parasites – Pneumocystis carinii, Toxoplasma gondii.
* Note: If Klebsiella pneumoniae is detected, also consider “Klebsiella pneumoniae associated invasive liver abscess syndrome”, which is rare in Europe and has only been reported in Asia.
