Table 3 Summary of diagnostic tests for Pneumocystis jirovecii pneumonia (PCP)
From: The role of rapid diagnostic tests in managing adults with pneumonia in low-resource settings
Test | Comments | Ref |
|---|---|---|
Microscopy | ||
Cell wall stains (e.g. Toluidine Blue O, calcofluor white) | Identification of cysts or trophozoites in BALF or lung biopsy specimens; ‘gold-standard’ diagnostic method. | |
Trophozoite stains (e.g. Grocott’s methenamine silver, Diff-Quick) | Immunofluorescence more sensitive than cytochemical stains. Only suitable for use with bronchoscopic or induced-sputum specimens. | |
Immunofluorescence | Training needed for accurate and consistent reporting. | |
Molecular assays | ||
PCR | Several genetic loci evaluated (e.g. mtLSUrRNA, HSP70, ITS, DHFR, MSG). | |
nPCR | High assay sensitivity may lead to false positive result if colonised with Pneumocystis; new quantitative assays have improved specificity. | |
qPCR | May be used with oral wash and upper respiratory tract specimens with reasonable sensitivity. | |
Serum assays | ||
1-3-β-D-glucan | Cell wall component of Pneumocystis; highly sensitive marker of PCP. Other invasive fungal infections and some antibiotics may cause false positive results. | |
S-adenosylmethionine | Essential metabolic intermediate; scavenged from host during active Pneumocystis infection such that serum levels are depleted. Poor diagnostic capability. |