Pneumonia laboratory findings
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Alejandro Lemor, M.D. [2]
Overview
Laboratory findings such as leukocytosis are helpful for the diagnosis of bacterial pneumonia or to assess the status of the patient. Sputum samples need to be collected from every patient and gram staining and culture need to be performed to determine the exact pathogen causing the pneumonia. Other tests include urine antigen test, PCR, C-reactive protein and procalcitonin.
Laboratory Tests
| Diagnostic Test | Indications | ||
|---|---|---|---|
| Sputum Culture |
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| Blood Culture |
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| Urinary Antigen Test for Pneumococcus |
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| Urinary Antigen Test for Legionella |
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| Adapted from IDSA/ATS Guidelines for CAP in Adults[1] | |||
Routine Tests
Findings in routine blood tests are based on the severity of the disease and the cause, they can include the following:[2]
- Leukocytosis with left shift (in cases of bacterial pneumonia)
- Leukopenia (in cases of atypical pneumonia)
- Eosinophilia (in cases of eosinophilic pneumonia)
- Anemia
- Hyponatremia
- Thrombocytopenia
- Elevated BUN
- Findings of lactic acidosis (decreased HCO3, increased lactic acid levels)
- ABG: may show hypoxia and/or hypercapnea
Sputum Gram Stain and Culture
- Sputum samples should be obtained of all patients with productive cough.
- Gram-stain and culture should be performed to assess the causative agent and guide the therapy.
- In more than 80% of cases of pneumococcal pneumonia the sputum culture is positive.[3]
Blood Culture
- Blood cultures should be obtained for patients with severe disease, patients that require hospitalization, and patients in which antibiotic therapy failed.
- Blood culture may be positive in cases of hematogenous spread, such as S. aureus pneumonia, and in around one fourth of patients with pneumococcal pneumonia.
Other Laboratory Tests
Urine Antigen Test [4]
- Usually used to diagnose Legionella disease.
- Useful also in the diagnosis of pneumonia caused by Streptococcus pneumoniae, with a sensitivity of 74.6% and an association with worst clinical outcome.[5]
- The presence of the antigen in urine can be detected in 24 hours since the onset of the symptoms
- The severity of Legionella disease increases the sensitivity of the urinary antigen test.
- Urinary antigen test is not recommended in the diagnosis of pneumococcal pneumonia in children due to the high rate of false-positive results.[6]
Polymerase Chain Reaction
- Polymerase chain reaction (PCR) is more useful in the diagnosis of viral and mycoplasma pneumonia.
C-Reactive Protein
- C-reactive protein (CRP) may be helpful to differentiate between bacterial from viral pneumonia.
- It has been reported that CRP is elevated (> 100 mg/L) in cases of bacterial pneumonia.[7]
Procalcitonin
- Procalcitonin levels are associated with the severity of the pneumonia and the etiology.
- This biomarker also helps to differentiate between bacterial and non-bacterial disease.[8]
References
- ↑ Mandell, L. A.; Wunderink, R. G.; Anzueto, A.; Bartlett, J. G.; Campbell, G. D.; Dean, N. C.; Dowell, S. F.; File, T. M.; Musher, D. M.; Niederman, M. S.; Torres, A.; Whitney, C. G. (2007). "Infectious Diseases Society of America/American Thoracic Society Consensus Guidelines on the Management of Community-Acquired Pneumonia in Adults". Clinical Infectious Diseases. 44 (Supplement 2): S27–S72. doi:10.1086/511159. ISSN 1058-4838.
- ↑ Solomon, Caren G.; Wunderink, Richard G.; Waterer, Grant W. (2014). "Community-Acquired Pneumonia". New England Journal of Medicine. 370 (6): 543–551. doi:10.1056/NEJMcp1214869. ISSN 0028-4793.
- ↑ Musher, Daniel M.; Thorner, Anna R. (2014). "Community-Acquired Pneumonia". New England Journal of Medicine. 371 (17): 1619–1628. doi:10.1056/NEJMra1312885. ISSN 0028-4793.
- ↑ Couturier MR, Graf EH, Griffin AT (2014). "Urine antigen tests for the diagnosis of respiratory infections: legionellosis, histoplasmosis, pneumococcal pneumonia". Clin Lab Med. 34 (2): 219–36. doi:10.1016/j.cll.2014.02.002. PMID 24856525.
- ↑ Zalacain R, Capelastegui A, Ruiz LA, Bilbao A, Gomez A, Uranga A; et al. (2014). "Streptococcus pneumoniae antigen in urine: diagnostic usefulness and impact on outcome of bacteraemic pneumococcal pneumonia in a large series of adult patients". Respirology. 19 (6): 936–43. doi:10.1111/resp.12341. PMID 24976113.
- ↑ Bradley JS, Byington CL, Shah SS, Alverson B, Carter ER, Harrison C; et al. (2011). "The management of community-acquired pneumonia in infants and children older than 3 months of age: clinical practice guidelines by the Pediatric Infectious Diseases Society and the Infectious Diseases Society of America". Clin Infect Dis. 53 (7): e25–76. doi:10.1093/cid/cir531. PMID 21880587.
- ↑ Flanders, Scott A; Stein, John; Shochat, Guy; Sellers, Karen; Holland, Miles; Maselli, Judith; Drew, W.Lawrence; Reingold, Art L; Gonzales, Ralph (2004). "Performance of a bedside c-reactive protein test in the diagnosis of community-acquired pneumonia in adults with acute cough". The American Journal of Medicine. 116 (8): 529–535. doi:10.1016/j.amjmed.2003.11.023. ISSN 0002-9343.
- ↑ Johansson, Niclas; Kalin, Mats; Backman-Johansson, Carolina; Larsson, Anders; Nilsson, Kristina; Hedlund, Jonas (2014). "Procalcitonin levels in community-acquired pneumonia – correlation with aetiology and severity". Scandinavian Journal of Infectious Diseases. 46 (11): 787–791. doi:10.3109/00365548.2014.945955. ISSN 0036-5548.