Lower Respiratory Tract Infection Risk Assessment

Using procalcitonin to aid in the management and monitoring of lower respiratory tract infections

Acute lower respiratory tract infections (LRTIs) include community-acquired pneumonia (CAP), acute bronchitis, and acute exacerbation of chronic obstructive pulmonary disease (AECOPD). LRTIs are primarily caused by viral or bacterial pathogens. 

It is reported that as many as 75% of patients with acute respiratory tract infections are treated with antibiotics even though the cause is mainly viral.1

The overuse and misuse of antibiotics—such as in cases where the infection is viral, or the clinical conditions are due to non-infectious causes—lowers their efficacy and promotes the spread of antibiotic resistant bacteria.

Procalcitonin (PCT) is a host response biomarker that is sensitive and specific to bacterial infection.2 In patients with suspected or confirmed LRTI, PCT can help to differentiate bacterial infection from other potential causes and aid in decision-making around the initiation and duration of antibiotic therapy.

PCT offers clinicians guidance to:

Initiate antibiotics

It is important to measure PCT levels at the first suspicion of infection to assess the likelihood of bacterial infection and need for antibiotic therapy. This will also help to determine severity of illness and risk for further progression of disease. Monitoring PCT levels helps to determine adequacy of source control and to early detect therapeutic failure.

Determine when it’s safe to discontinue antibiotics

Paired with clinical assessment, B·R·A·H·M·S PCT™ is the only FDA-cleared PCT and CE-certified assay to aid in decisions about initiating and/or discontinuing antibiotic therapy for patients with suspected or confirmed LRTI.5

PCT for differential diagnosis of LRTIs3,4

PCT < 0.10 ng/mL

Indicates absence of bacterial infection.*
The use of antibiotics strongly discouraged, also in the presence of imparted pulmonary reserve in AECOPD.

PCT > 0.10 - < 0.25 µg/L

Bacterial infection unlikely.*
The use of antibiotics is discouraged.

PCT > 0.25 - < 0.5 µg/L

Bacterial infection possible.*
Advice to initiate antimicrobial therapy.

PCT ≥ 0.5 µg/L

Suggestive of the presence of bacterial infection.*
Antimicrobial treatment strongly recommended.

Changes in PCT
plasma concentration

Current PCT
plasma concentration

Decline from peak
PCT > 80%
and clinical improvement


LRTI ≤ 0.25ng/mL
Discontinue antibiotics

Sepsis ≤ 0.50ng/mL
Discontinue antibiotics

PCT-supported therapy has been shown to reduce inpatient antibiotic exposure by 35% for LRTI patients without negative effects for mortality or length of stay.1,5-14

*PCT levels below 0.25 µg/L do not exclude an infection, because localized infections (without systemic signs) may also be associated with such low levels. In addition, if the PCT measurement is done very early after the systemic infection process has started (usually <6 hours), values may still be low. The PCT reference ranges are valuable guidelines for the clinician but they should always be interpreted in the context of the patient’s clinical condition. Antibiotic treatment should be started or continued on suspicion of infection, particularly in high-risk patients.

*PCT values may be elevated in certain conditions independent of bacterial infection. Decisions regarding antibiotic therapy should NOT be based solely on procalcitonin concentrations.23 Important considerations when interpreting PCT results.

Reducing antibiotic prescription rate and duration in LRTI

PCT has been shown to reduce antibiotic prescription rates and duration in LRTI. In the multicentric, randomized  controlled, interventional ProHosp trial (n=1359), antibiotic duration and antibiotic prescription rates were significantly reduced in the PCT group in comparison to the standard-of-care group for community-acquired pneumonia (CAP) (n=925), acute exacerbations of COPD (n=228), and bronchitis (n=151), resulting in an overall reduction of antibiotic exposure by 34.8% versus standard-of-care.1

Evidence has shown PCT to be a valuable tool during the COVID-19 pandemic. The data reports that PCT aids in early identification of patients at low risk of bacterial infection on admission as well as assists in detection of bacterial coinfection in hospitalized patients.

PCT and LRTI guidelines

Infectious Diseases Society of America (IDSA)

Management of adults with hospital-acquired and ventilator-associated pneumonia: 2016 Clinical Practice Guidelines by the Infectious Diseases Society of America and the American Thoracic Society

In section XXIV: Should discontinuation of antibiotic therapy be based upon PCT levels plus clinical criteria or clinical criteria alone in patients with HAP/VAP?15

Recommendation: For patients with HAP/VAP, we suggest using PCT levels plus clinical criteria to guide the discontinuation of antibiotic therapy, rather than clinical criteria alone.15

Second World Health Organization (WHO) Model List of Essential In Vitro Diagnostics

The WHO recognizes that in vitro diagnostics (IVDs) are essential for advancing universal health coverage, addressing health emergencies, and promoting healthier populations, which are the three strategic priorities of the Thirteenth WHO General Programme of Work, 2019-2023.17

Recommendation: PCT to guide antibiotic therapy or discontinuation in sepsis and lower respiratory tract infection (for use only in tertiary care facilities and above)17

European Society of Cardiology (ESC): Acute and Chronic Heart Failure Guidelines

Recommendation: Assessment of PCT levels may be considered in patients with acute heart failure with suspected coexisting infection, particularly for the differential diagnosis of pneumonia and to guide antibiotic therapy, if considered.18,19

Helpful resources

Learn more about implementing procalcitonin testing in your hospital.
Learn more about implementing procalcitonin testing in your hospital.
  1. Schuetz P, Christ-Crain M, Thomann R. Effect of procalcitonin-based guidelines vs standard guidelines on antibiotic use in lower respiratory tract infections: The proHOSP randomized controlled trial. JAMA. 2009 Sep 9;302(10):1059-66.  
  2. Brunkhorst FM, Heinz U, Forycki ZF. Kinetics of procalcitonin in iatrogenic sepsis. Intensive Care Med 1998 Aug;24(8):888-889.
  3. Meisner M. Procalcitonin-biochemistry and clinical diagnosis. Dresden (Germany): UNI-MED-Verlag; 2010.
  4. Christ-Crain M, Jaccard-Stolz D, Bingisser R, Gencay MM, Huber PR, Tamm M, et al. Effect of procalcitonin-guided treatment on antibiotic use and outcome in lower respiratory tract infections: Cluster-randomised, single-blinded intervention trial. Lancet Infect Dis. 2004 Feb 21;363(9409):600-7.
  5. Briel M, Schuetz P, Mueller B, Young J, Schild U, Nusbaumer C, et al. Procalcitonin-guided antibiotic use vs a standard approach for acute respiratory tract infections in primary care. Arch Intern Med. 2008 Oct 13;168(18):2000-7.
  6. Burkhardt O, Ewig S, Haagen U, Giersdorf S, Hartmann O, Wegscheider K, et al. Procalcitonin guidance and reduction of antibiotic use in acute respiratory tract infection. 2010 Sep 1;36(3):601-7.
  7. Christ-Crain M, Stolz D, Bingisser R, Müller CH, Miedinger D, Huber PR, et al. Procalcitonin guidance of antibiotic therapy in community-acquired pneumonia: a randomized trial. Am J Respir Crit Care Med. 2006 Jul 1;174(1):84-93.
  8. Hochreiter M, Köhler T, Schweiger AM, Keck FS, Bein B, von Spiegel T, et al. Procalcitonin to guide duration of antibiotic therapy in surgical intensive care patients: A randomized prospective controlled trial. Crit Care. 2009. Jun;13(3):1-7.
  9. Kristoffersen KB, Søgaard OS, Wejse C, Black FT, Greve T, Tarp B, et al. Antibiotic treatment interruption of suspected lower respiratory tract infections based on a single procalcitonin measurement at hospital admission–a randomized trial. Clin Microbiol. Infect. 2009 May; 15(5): 481-7.
  10. Long W, Deng X, Zhang YU, Lu G, Xie J, Tang J. Procalcitonin guidance for reduction of antibiotic use in low-risk outpatients with community-acquired pneumonia. Respirology. 2011 Jul; 16(5): 819-24.
  11. Nobre V, Harbarth S, Graf JD, Rohner P, Pugin J. Use of procalcitonin to shorten antibiotic treatment duration in septic patients: A randomized trial. Am J Resp Crit Care Med. 2008 Mar 1;177(5):498-505.
  12. Schroeder S, Hochreiter M, Koehler T, Schweiger AM, Bein B, Keck FS, et al. Procalcitonin (PCT)-guided algorithm reduces length of antibiotic treatment in surgical intensive care patients with severe sepsis: Results of a prospective randomized study. Langenbecks Arch Surg. 2009 Mar 1;394(2):221-6.
  13. Stolz D, Christ-Crain M, Bingisser R, Leuppi J, Miedinger D, Müller C, et al. Antibiotic treatment of exacerbations of COPD: a randomized, controlled trial comparing procalcitonin-guidance with standard therapy. Chest. 2007 Jan 1;131(1):9-19.
  14. Stolz D, Smyrnios N, Eggimann P, Pargger H, Thakkar N, Siegemund M, et al. Procalcitonin for reduced antibiotic exposure in ventilator-associated pneumonia: A randomised study. Eur Respir J. 2009 Dec 1;34(6):1364-75.
  15. Kalil AC, Metersky ML, Klompas M, Muscedere J, Sweeney DA, Palmer LB, et al. Management of adults with hospital-acquired and ventilator-associated pneumonia: 2016 clinical practice guidelines by the Infectious Diseases Society of America and the American Thoracic Society. Clin Infect Dis. 2016 Sep 1;63(5):e61-111.
  16. Metlay JP, Waterer GW, Long AC, Anzueto A, Brozek J, Crothers K, et al. Diagnosis and treatment of adults with community-acquired pneumonia. An official clinical practice guideline of the American Thoracic Society and Infectious Diseases Society of America. Am J Respir Crit Care Med. 2019 Oct 1;200(7):e45-67.
  17. Second WHO Model List of Essential In Vitro Diagnostics [Internet]. World Health Organization. World Health Organization; 2020 [cited 2020Dec21]. Available here.
  18. Maisel A, Neath SX, Landsberg J, Mueller C, Nowak RM, Peacock WF, et al. Use of procalcitonin for the diagnosis of pneumonia in patients presenting with a chief complaint of dyspnoea: Results from the BACH (Biomarkers in Acute Heart Failure) trial. Eur J Heart Fail 2012;14: 278–286.
  19. Ponikowski P, Voors AA, Anker SD, Bueno H, Cleland JG, Coats AJ, et al. 2016 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure: The Task Force for the diagnosis and treatment of acute and chronic heart failure of the European Society of Cardiology (ESC) Developed with the special contribution of the Heart Failure Association (HFA) of the ESC. Eur Heart J. 2016 Jul 14;37(27):2129-200.
  20. Thermo Fisher Scientific. B·R·A·H·M·S GmbH, B·R·A·H·M·S PCT sensitive KRYPTOR® Instruction for Use (Version 19.0us) [Internet]. 2018. Available here.
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