Diagnosing Pneumocystis jirovecii pneumonia: A review of current methods and novel approaches

Abstract

Pneumocystis jirovecii can cause life-threatening pneumonia in immunocompromised patients. Traditional diagnostic testing has relied on staining and direct visualization of the life-forms in bronchoalveolar lavage fluid. This method has proven insensitive, and invasive procedures may be needed to obtain adequate samples. Molecular methods of detection such as polymerase chain reaction (PCR), loop-mediated isothermal amplification (LAMP), and antibody-antigen assays have been developed in an effort to solve these problems. These techniques are very sensitive and have the potential to detect Pneumocystis life-forms in noninvasive samples such as sputum, oral washes, nasopharyngeal aspirates, and serum. This review evaluates 100 studies that compare use of various diagnostic tests for Pneumocystis jirovecii pneumonia (PCP) in patient samples. Novel diagnostic methods have been widely used in the research setting but have faced barriers to clinical implementation including: interpretation of low fungal burdens, standardization of techniques, integration into resource-poor settings, poor understanding of the impact of host factors, geographic variations in the organism, heterogeneity of studies, and limited clinician recognition of PCP. Addressing these barriers will require identification of phenotypes that progress to PCP and diagnostic cut-offs for colonization, generation of life-form specific markers, comparison of commercial PCR assays, investigation of cost-effective point of care options, evaluation of host factors such as HIV status that may impact diagnosis, and identification of markers of genetic diversity that may be useful in diagnostic panels. Performing high-quality studies and educating physicians will be crucial to improve the rates of diagnosis of PCP and ultimately to improve patient outcomes.

Detection of Pneumocystis jirovecii and Other Agents in Bronchoalveolar Lavage Samples of HIV- Negative Immuncompromised Patients

“…Pneumocystis pnömonisi, HIV negatif genel durumu bozuk hastalarda mortalitesinin yüksek olması nedeniyle önemlidir. Yapılan çalışmalarda, HIV pozitif hastalarda mortalite %7-20'iken, HIV negatif genel durumu bozuk hastalarda mortalite %29-60 olarak bulunmuştur (25) . Bu nedenle, üçüncü basamak hastanelerde solunum yolu örneklerinde, özellikle altın standart olan BAL örneklerinde P. jirovecii'nin aranması gerekir.…”

A New PCR-Based Assay for Testing Bronchoalveolar Lavage Fluid Samples from Patients with Suspected Pneumocystis jirovecii Pneumonia

“…These findings would be consistent with the lower Ct values observed in these samples, which might reflect a smaller burden of PJ organisms, thus resulting in false-negative results at the microscopic examination. Six of seven patients were patients not living with HIV ( Table 1 ), which is a condition notoriously associated with a larger burden of PJ organisms in respiratory samples [ 3 ]. Therefore, we did not interpret the seven IFA negative results as falsely PCR positive results but as the results of patients who had benefited from the molecular rather than the microscopic diagnosis of PCP [ 4 ].…”

“…The non-specificity of either respiratory symptoms or imaging features necessitates differentiation among possible infectious etiologies as well as between infectious and non-infectious respiratory abnormalities [ 1 ]. Molecular-based methods for detecting pneumonia agents in multiple or single assays have been developed to overcome the limits of conventional (microscopy- or culture-based) identification methods, which are familiar in medical mycology [ 2 ] especially with PJ organisms [ 3 ].…”

Diagnostic Performance of Bronchoalveolar Lavage (1,3)-β-d-Glucan Assay for Pneumocystis jirovecii Pneumonia

“…This appears to be an even greater problem when BALF is tested, as noted in our study, and reported by others [ 12 ]. The reasons for false positive results are related, in part, to the sharing of similar glucans among various fungi and to similar substances on cellulose membranes, gauze packing material, and Gram-negative bacterial cell walls [ 14 ]. Why specificity is lower in BALF than serum is not clear.…”