Open Access Open Badges Research article

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

Yasuo Shimizu134*, Noriaki Sunaga1, Kunio Dobashi2, Makoto Fueki3, Naoto Fueki3, Sohei Makino34 and Masatomo Mori1

Author Affiliations

1 Department of Medicine and Molecular Science, Gunma University Graduate School of Medicine, 3-39-15 Showa-machi, Maebashi Gunma 371-8511, Japan

2 Gunma University School of Health Sciences, 3-39-15 Showa-machi, Maebashi Gunma 371-8511, Japan

3 Jobu Hospital for Respiratory Disease 586-1 Taguchi-machi, Maebashi, Gunma 371-0048, Japan

4 WHO Collaborating Center of Prevention and Control of Chronic Respiratory Diseases, Dokkyo University, (DU-WCC) 880 Kitakobayashi Mibu Shimotsuga-gun, Tochigi 321-0293, Japan

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BMC Infectious Diseases 2009, 9:47  doi:10.1186/1471-2334-9-47

Published: 22 April 2009



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.


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) β-D-glucan (β-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.


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 β-D-glucan level and lymphocyte count differed between patients with Pneumocystis pneumonia or P. jirovecii colonization.


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