Serum procalcitonin distinguishes CAP due to bacteria, Mycobacterium tuberculosis and PJP

Int J Tuberc Lung Dis. 2006 May;10(5):510-5.


Setting: Procalcitonin (PCT), a propeptide of the hormone calcitonin, is a novel marker of the inflammatory response to infection. It has been used to discriminate between infectious and non-infectious causes of inflammation, and as a marker of severe sepsis in the intensive care unit.

Objective: To evaluate the utility of PCT in distinguishing community-acquired pneumonia (CAP) due to common bacteria, Mycobacterium tuberculosis and Pneumocystis jirovecii in a high human immunodeficiency virus (HIV) prevalence setting.

Methods: Two hundred and sixty-six patients admitted with a diagnosis of CAP were investigated. Serum samples for PCT were collected on admission. PCT levels were measured using a commercial immunoluminometric assay.

Results: A microbiological diagnosis was obtained in 169/266 patients: 44 pulmonary tuberculosis (PTB), 31 P. jirovecii pneumonia (PJP), and 35 bacterial pneumonia. The PCT levels were PTB 4.16 ng/ml (SEM 1.197; 95% CI 1.749-6.579); PJP 1.138 ng/ml (SEM 0.2911; 95% CI 0.543-1.734); and bacterial pneumonia 19.48 ng/ml (SEM 5.64; 95% CI 8.021-30.938, P < 0.0004). Thirty-six had co-infections.

Conclusion: PCT levels differ significantly in patients with CAP due to TB, PJP and bacteria. PCT may be important in distinguishing M. tuberculosis and PJP in a high HIV prevalence setting where atypical presentations often confound the empirical clinical diagnosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analysis of Variance
  • Calcitonin / blood*
  • Calcitonin Gene-Related Peptide
  • Community-Acquired Infections / blood
  • Community-Acquired Infections / epidemiology
  • Community-Acquired Infections / microbiology*
  • Diagnosis, Differential
  • Female
  • HIV Seropositivity / complications
  • HIV Seropositivity / epidemiology
  • Humans
  • Male
  • Mycobacterium tuberculosis*
  • Pneumocystis carinii*
  • Pneumonia, Bacterial / blood
  • Pneumonia, Bacterial / epidemiology
  • Pneumonia, Bacterial / microbiology*
  • Prevalence
  • Prospective Studies
  • Protein Precursors / blood*
  • South Africa / epidemiology
  • Statistics, Nonparametric


  • CALCA protein, human
  • Protein Precursors
  • Calcitonin
  • Calcitonin Gene-Related Peptide