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Quantitative real-time PCR and the (1→3)-β-D-glucan assay for differentiation between Pneumocystis jirovecii
1Department of Clinical Laboratory Medicine, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Abstract:
We evaluated whether quantitative PCR (qPCR) and (1 → 3)-β-d-glucan assays could be used to differentiate Pneumocystis pneumonia (PCP) from Pneumocystis jirovecii colonization in immunocompromised patients with pulmonary infiltrates. A total of 40 bronchoalveolar lavage samples and 107 induced sputum samples from 147 patients who were suspected of having PCP were obtained for PCR detection of P. jirovecii. Diagnoses of definite PCP, probable PCP, pneumonia with P. jirovecii colonization (colonization) and pneumonia without colonization (non-colonization) were made in 11, 42, 15 and 60 patients, respectively. A PCP diagnosis was undetermined in 19 patients. The copy numbers, determined using qPCR, were significantly higher in definite PCP and probable PCP patients than in colonized patients. The area under the receiver-operating characteristic curve (AUC), sensitivity and specificity for discriminating definite PCP from colonization were 0.96, 100.0% and 80.0%, respectively, at a cut-off value of 1300 copies/mL. The values for discriminating probable PCP from colonization were 0.71, 66.7% and 73.3%, respectively, at a cut-off value of 340 copies/mL. β-d-glucan levels were significantly higher in patients with both definite PCP and probable PCP than in colonized patients. The AUC, sensitivity and specificity for discriminating definite PCP were 0.91, 100.0% and 80.0%, respectively, at a cut-off value of 15.6 pg/mL. The values for discriminating probable PCP were 0.78, 76.2% and 73.3%, respectively, at a cut-off value of 6.0 pg/mL. Both qPCR and the β-d-glucan assay displayed high accuracy for discriminating colonization from definite PCP and displayed moderate accuracy for discriminating colonization from probable PCP.
Insights
Quantitative PCR (qPCR) and β-d-glucan assays accurately differentiate Pneumocystis pneumonia (PCP) from colonization in immunocompromised patients. These methods show high accuracy for definite PCP and moderate accuracy for probable PCP, aiding diagnosis.
Area of Science:
- Medical diagnostics
- Clinical microbiology
- Infectious diseases
Background:
- Pneumocystis pneumonia (PCP) is a serious opportunistic infection.
- Differentiating PCP from colonization is crucial for appropriate treatment in immunocompromised patients.
- Pulmonary infiltrates in immunocompromised individuals necessitate accurate etiological diagnosis.
Purpose of the Study:
- To evaluate the utility of quantitative PCR (qPCR) and (1 → 3)-β-d-glucan assays in distinguishing PCP from Pneumocystis jirovecii colonization.
- To determine the diagnostic accuracy, sensitivity, and specificity of these assays for definite and probable PCP cases.
Main Methods:
- Analysis of bronchoalveolar lavage and induced sputum samples from 147 patients suspected of PCP.
- Detection and quantification of Pneumocystis jirovecii using qPCR.
- Measurement of (1 → 3)-β-d-glucan levels in patient samples.
- Statistical analysis including ROC curve analysis to assess diagnostic performance.
Main Results:
- qPCR copy numbers were significantly higher in definite and probable PCP patients compared to colonized patients.
- The qPCR assay showed high accuracy (AUC 0.96) for definite PCP vs. colonization at 1300 copies/mL.
- β-d-glucan levels were significantly elevated in PCP patients versus colonized patients, with high accuracy (AUC 0.91) for definite PCP at 15.6 pg/mL.
Conclusions:
- Both qPCR and β-d-glucan assays are valuable tools for differentiating Pneumocystis pneumonia from colonization.
- These assays demonstrate high accuracy in distinguishing definite PCP from colonization.
- Moderate accuracy was observed for differentiating probable PCP from colonization, suggesting their utility in clinical decision-making.
