Chest
Volume 131, Issue 4, April 2007, Pages 1173-1180
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Original Research
Respiratory Infections
Serum Indicators for the Diagnosis of Pneumocystis Pneumonia

https://doi.org/10.1378/chest.06-1467Get rights and content

Background

The diagnosis of pneumocystis pneumonia (PCP) is difficult because it requires microscopic examination to identify pneumocystis from induced sputum or BAL fluid.

Study objective

To evaluate the usefulness of four serum markers—lactate dehydrogenase (LDH), (1→3) β-D-glucan (β-D-glucan), KL-6, and C-reactive protein (CRP)—in the diagnosis of PCP.

Design

Case-control retrospective study.

Patients and measurements

We reviewed the medical records of 295 consecutive patients who underwent BAL for the diagnosis of PCP. Differential cell counts in BAL fluid and serum levels of LDH, β-D-glucan, KL-6, and CRP were examined. Oxygenation index was determined using arterial oxygen tension and inspiratory oxygen concentration.

Results

Based on the microscopic examination of BAL fluid, 57 patients were PCP positive and 238 patients were PCP negative. There were no significant differences in cell count or differentials in BAL fluid between the positive and negative cases. Serum levels of LDH, β-D-glucan, and KL-6 were significantly higher in PCP-positive patients (p < 0.01). Receiver operating characteristic curves suggest that β-D-glucan was the most reliable indicator. The cut-off level of β-D-glucan was estimated to be 31.1 pg/mL, with which the positive and negative predictive values were 0.610 and 0.980, respectively. In PCP-positive patients, the oxygenation index was decreased and correlated with LDH. Both LDH and β-D-glucan levels were correlated with the proportion of neutrophils in BAL fluid.

Conclusions

Serum β-D-glucan is a reliable marker for the diagnosis of PCP. Since BAL procedure is invasive, measuring β-D-glucan should be considered as a primary modality for a diagnosis of PCP, especially for patients with severe respiratory failure.

Section snippets

Patient Selection

We retrospectively evaluated data from 295 consecutive patients who underwent BAL for the diagnosis of PCP at Keio University Hospital (Tokyo, Japan) during the period from April 1998 until October 2005.

Data Collection

We reviewed the medical records of all the patients evaluated for demographic, BAL, and serum data. The following data were collected: age, sex, and underlying disease. The BAL data included the recovery of the fluid, which is the volume ratio of the saline solution recovered to the saline

Results

During the study period, PCP was diagnosed in 57 patients based on microscopic findings in BAL specimens. A total of 238 patients were PCP negative, 16 of whom were empirically treated with trimethoprim/sulfamethoxazole or pentamidine due to persistent suspicion about PCP or failure of the preceding treatment. Data from these 16 patients were excluded from the analysis because it was thought that they may have had PCP. All of the PCP-positive patients were treated initially with

Discussion

In the present study, we evaluated the roles of the serum markers LDH, β-D-glucan, KL-6, and CRP in the diagnosis of PCP. Although there have been several reports135691013 describing the levels of serum markers in PCP patients, the diagnostic significance of serum markers, including the newly identified β-D-glucan and KL-6, remains to be evaluated in a larger cohort of patients with a variety of underlying diseases.

The results of this study revealed that β-D-glucan is the most reliable

ACKNOWLEDGMENT

We thank Dr. Gregory A. Plotnikoff for review of the manuscript. We also thank Dr. Satoru Fukinbara for contributing to the statistical analysis.

References (19)

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None of the authors have any conflicts of interest to disclose.

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