title: Serum procalcitonin distinguishes CAP due to bacteria, Mycobacterium tuberculosis and PJP.
abstract: METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Medicine, Nelson R Mandela School of Medicine, Faculty of Health Sciences, University of KwaZulu-Natal, Durban, South Africa.
authors.forename: K
authors.initials: K
authors.lastname: Nyamande
authors.forename: U G
authors.initials: UG
authors.lastname: Lalloo
mesh_terms: D000704:Analysis of Variance; D002116:Calcitonin / Q000097:blood*; D015740:Calcitonin Gene-Related Peptide; D017714:Community-Acquired Infections / Q000097:blood / Q000453:epidemiology / Q000382:microbiology*; D003937:Diagnosis, Differential; D005260:Female; D006679:HIV Seropositivity / Q000150:complications / Q000453:epidemiology; D006801:Humans; D008297:Male; D009169:Mycobacterium tuberculosis; D045363:Pneumocystis carinii; D018410:Pneumonia, Bacterial / Q000097:blood / Q000453:epidemiology / Q000382:microbiology*; D015995:Prevalence; D011446:Prospective Studies; D011498:Protein Precursors / Q000097:blood*; D013019:South Africa / Q000453:epidemiology; D018709:Statistics, Nonparametric
chemical_list: C000606589:CALCA protein, human; D011498:Protein Precursors; D002116:Calcitonin; D015740:Calcitonin Gene-Related Peptide