Combination of β‐(1, 3)‐D‐glucan testing in serum and qPCR in nasopharyngeal aspirate for facilitated diagnosis of Pneumocystis jirovecii pneumonia

Abstract

Summary Background Currently, the biological diagnosis of Pneumocystis jirovecii pneumonia (PjP infection) usually relies on microbiological investigations in bronchial‐alveolar lavage fluid (BALF) by conventional staining methods and/or molecular biology. However, bronchial‐alveolar lavage is sometimes complicated to manage, especially in weakened patients. Therefore, alternative clinical samples—easier to collect—are warranted in such specific contexts. Objective Over a four‐year period, diagnostic performance of an original method based on combination of quantitative real‐time polymerase chain reaction (qPCR) in nasopharyngeal aspirate (NPA) with measurement of β‐(1, 3)‐D‐glucan antigen (BDG) in serum was prospectively assessed in a single centre. Patients/methods Results were compared with those obtained in BALF through direct staining methods and qPCR. True positives were defined by an independent committee based on clinical, radiological and biological data. Overall, 48 individuals with a definitive diagnosis of PjP infection were included, and 48 controls were selected upon matching for age, sex and underlying disease(s). Results qPCR results were strongly correlated between BALF and NPA (P < .0001). Altogether, greater diagnostic performance was achieved when establishing the positive cut‐off of BDG antigen at 143 pg/mL. In such conditions, sensitivity of the testing based on either positive BDG measurement or positive qPCR in NPA was then calculated at 93.75%, 95%CI [82.37%‐98.40%], and specificity at 97.87%, 95%CI [87.66%‐100.00%]. Conclusions Further validation through multicentre studies is now required, especially for establishing clear cut‐offs. However, one could already state that combination of qPCR in the NPA with BDG measurement in serum may be a valuable substitute for BALF examination.

Non-invasive diagnosis of Pneumocystis jirovecii pneumonia: a systematic review and meta-analysis

“…Nasopharyngeal aspirate and oral wash PCR sensitivities were both numerically lower than induced sputum PCR, at 89% and 77% (compared to 99%), respectively, but had similar J o u r n a l P r e -p r o o f specificities. It is important to recognize that studies reporting on nasopharyngeal aspirates [35,56] consisted of true aspirates (as opposed to swabs); thus, the diagnostic accuracy of nasal swab PCR still requires separate investigation. Oral wash PCR performed similarly to what has been described previously in a smaller meta-analysis of 4 studies [77] when compared with our studies.…”

“…It has been suggested that quantitative PCR (qPCR) or realtime PCR (RT-PCR) could be used to discern active infection from colonization, although this has yet to be proven [79]. Owing to the lower fungal burden in minimally invasive samples compared to BAL [35], one could hypothesize that the risk of false positive might be lower using a minimally invasive specimen compared to BAL, but this needs to be specifically investigated. This could explain why the specificities for non-invasive PCR appeared to be higher (94-98%) than those reported for BAL PCR (91%) [9], as has been described previously [78].…”

Diagnostic accuracy of serum (1-3)-β-D-glucan for Pneumocystis jirovecii pneumonia: a systematic review and meta-analysis

“…The overall specificity of 79% is lower that the subgroup-specific specificity for HIV (83%; 95%CI 69e92%) and non-HIV (83%; 95%CI 72e90%). This is because there are five studies [22,25,33,36,42] included in the overall estimates that include HIV-positive patients but do not provide stratified data.…”

Diagnostic accuracy of (1→3)-β-D-glucan to predict Pneumocystis jirovecii pneumonia in non-HIV-infected patients

“…26 It was recently shown that serum (1→3)-β-D-glucan levels of 143 pg/mL can be used to distinguish PCP from colonisation with P. jirovecii. 28 To diagnose and treat PCP you have to have a lot of experience. 29 Our results were not concordant with latter studies because we measured much higher (1→3)-β-D-glucan levels in the patients with true PCP.…”