(1–3)-Beta-D-glucan in association with lactate dehydrogenase as biomarkers of Pneumocystis pneumonia (PcP) in HIV-infected patients

Abstract

Pneumocystis pneumonia (PcP) is a major HIV-related illness caused by Pneumocystis jirovecii. Definitive diagnosis of PcP requires microscopic detection of P. jirovecii in pulmonary specimens. The objective of this study was to evaluate the usefulness of two serum markers in the diagnosis of PcP. Serum levels of (1-3)-beta-d-glucan (BG) and lactate dehydrogenase (LDH) were investigated in 100 HIV-positive adult patients and 50 healthy blood donors. PcP cases were confirmed using indirect immunofluorescence with monoclonal anti-Pneumocystis antibodies and nested-PCR to amplify the large subunit mitochondrial rRNA gene of P. jirovecii in pulmonary specimens. BG and LDH levels in serum were measured using quantitative microplate-based assays. BG and LDH positive sera were statistically associated with PcP cases (P ≤ 0.001). Sensitivity, specificity, positive/negative predictive values (PPV/NPV), and positive/negative likelihood ratios (PLR/NLR) were 91.3 %, 61.3 %, 85.1 %, 79.2 %, 2.359, and 0.142, respectively, for the BG kit assay, and 91.3 %, 35.5 %, 75.9 %, 64.7 %, 1.415 and 0.245, respectively, for the LDH test. Serologic markers levels combined with the clinical diagnostic criteria for PcP were evaluated for their usefulness in diagnosis of PcP. The most promising cutoff levels for diagnosis of PcP were determined to be 400 pg/ml of BG and 350 U/l of LDH, which combined with clinical data presented 92.8 % sensitivity, 83.9 % specificity, 92.8 % PPV, 83.9 % NPV, 5.764 PLR and 0.086 NLR (P < 0.001). This study confirmed that BG is a reliable indicator for detecting P. jirovecii infection. The combination between BG/LDH levels and clinical data is a promising alternative approach for PcP diagnosis.

Diagnosis of Pneumocystis pneumonia: evaluation of four serologic biomarkers

“…The present results are consistent with a previous report on the usefulness of BG levels for PcP diagnosis in Portuguese HIV-positive patients in which the sensitivity and specificity of the BG test (cut-off value of 100 pg/ml) were 89.9% and 71.0%, respectively [7]. Even being a structural molecule of P. jirovecii cell wall, BG is not a species-specific marker, presenting a panfungal character, which is one of the explanations for the false-positive cases and the relatively low specificity rates for the diagnosis of PcP [7,18,21]. Additionally, it was suggested by other authors that false-positive cases may also be caused by the administration of certain agents that are filtered through cellulose membranes [22].…”

“…Receiver operating characteristic (ROC) curves, sensitivity, specificity, positive/negative predictive values (PPV/NPV) and the positive/negative likelihood ratios (PLR/NLR) were calculated to assess the utility of BG, KL-6, LDH and SAM serum levels for PcP diagnosis [7,21].…”

“…BG, KL-6, LDH and SAM levels were determined by using the FUNGITELL™ Assay (Associates of Cape Cod, Inc. USA), ELISA assay KL-6 antibody kit (Eisai Co., Japan), Lactate Dehydrogenase Assay Kit (BioVision, USA) and ELISA SAM antibody kit (EIAab Co., China), respectively. The cut-off reference values of the BG (100 pg/ml) and LDH (350 U/l) assays were defined according to a previous a report [7,14,19], while the cut-off values of the KL-6 (580 U/ml) and SAM (50 nmol/l) assays were defined according to the sensitivity/specificity analysis of the present study.…”

“…In the Spanish COPD patients, detection of P. jirovecii was performed by nested-PCR directed to the mtLSU rRNA gene [33]. [2,7,13].…”

“…A clinical diagnosis of PcP was considered when at least two of the following variables were present: symptoms such as unproductive cough, fever and dyspnea; arterial partial pressure of oxygen (PaO 2 ) lower than 65 mmHg; and chest radiographs presenting fine bilateral, perihilar interstitial shadowing [6,7,32].…”