Serum markers in interstitial pneumonia with and without Pneumocystis jirovecii colonization: a prospective study

BMC Infect Dis. 2009 Apr 22;9:47. doi: 10.1186/1471-2334-9-47.


Background: In patients with chronic respiratory disease, Pneumocystis jirovecii (P. jirovecii) colonization is observed, and may influence disease progression and systemic inflammation. Pneumocystis pneumonia causes interstitial changes, so making a diagnosis of PCP in patients who have interstitial pneumonia (IP) with P. jirovecii colonization is sometimes difficult based on radiography.

Methods: This study investigated the prevalence of P. jirovecii colonization in IP patients and assessed pulmonary injury due to P. jirovecii colonization by measurement of serum markers (KL-6, SP-A, SP-D, and (1-->3) beta-D-glucan (beta-D-glucan)) and the peripheral lymphocyte counts, prospectively. A total of 75 patients with idiopathic pulmonary fibrosis (n = 29), collagen vascular-related interstitial pneumonia (n = 19), chronic bronchitis or pneumonia (n = 20), and Pneumocystis pneumonia (n = 7) were enrolled in this prospective study. P. jirovecii DNA was detected in sputum samples, while serum markers and the lymphocyte count were measured in the peripheral blood.

Results: IP patients (idiopathic pulmonary fibrosis and collagen vascular-related IP) who received oral corticosteroids had a high prevalence of P. jirovecii colonization (23.3%). In IP patients, oral corticosteroid therapy was a significant risk factor for P. jirovecii colonization (P < 0.05). Serum markers did not show differences between IP patients with and without P. jirovecii colonization. The beta-D-glucan level and lymphocyte count differed between patients with Pneumocystis pneumonia or P. jirovecii colonization.

Conclusion: Serum levels of KL-6, SP-A, SP-D, and beta-D-glucan were not useful for detecting P. jirovecii colonization in IP patients. However, the serum beta-D-glucan level and lymphocyte count were useful for distinguishing P. jirovecii colonization from pneumocystis pneumonia in IP patients.

MeSH terms

  • Adrenal Cortex Hormones / therapeutic use
  • Aged
  • Biomarkers / blood*
  • Female
  • Humans
  • Idiopathic Pulmonary Fibrosis / blood
  • Idiopathic Pulmonary Fibrosis / diagnosis*
  • Idiopathic Pulmonary Fibrosis / drug therapy
  • Idiopathic Pulmonary Fibrosis / microbiology
  • Lymphocyte Count
  • Male
  • Middle Aged
  • Pneumocystis carinii / isolation & purification*
  • Pneumonia, Pneumocystis / blood
  • Pneumonia, Pneumocystis / diagnosis*
  • Prevalence
  • Prospective Studies
  • Risk Factors
  • beta-Glucans / blood


  • Adrenal Cortex Hormones
  • Biomarkers
  • beta-Glucans