Diagnosis of Pneumocystis jirovecii pneumonia with serum cell-free DNA in non-HIV-infected immunocompromised patients

Computed tomography-based radiomics improves non-invasive diagnosis of Pneumocystis jirovecii pneumonia in non-HIV patients: a retrospective study

BACKGROUND

Pneumocystis jirovecii pneumonia (PCP) could be fatal to patients without human immunodeficiency virus (HIV) infection. Current diagnostic methods are either invasive or inaccurate. We aimed to establish an accurate and non-invasive radiomics-based way to identify the risk of PCP infection in non-HIV patients with computed tomography (CT) manifestation of pneumonia.

METHODS

This is a retrospective study including non-HIV patients hospitalized for suspected PCP from January 2010 to December 2022 in one hospital. The patients were randomized in a 7:3 ratio into training and validation cohorts. Computed tomography (CT)-based radiomics features were extracted automatically and used to construct a radiomics model. A diagnostic model with traditional clinical and CT features was also built. The area under the curve (AUC) were calculated and used to evaluate the diagnostic performance of the models. The combination of the radiomics features and serum β-D-glucan levels was also evaluated for PCP diagnosis.

RESULTS

A total of 140 patients (PCP: N = 61, non-PCP: N = 79) were randomized into training (N = 97) and validation (N = 43) cohorts. The radiomics model consisting of nine radiomic features performed significantly better (AUC = 0.954; 95% CI: 0.898-1.000) than the traditional model consisting of serum β-D-glucan levels (AUC = 0.752; 95% CI: 0.597-0.908) in identifying PCP (P = 0.002). The combination of radiomics features and serum β-D-glucan levels showed an accuracy of 95.8% for identifying PCP infection (positive predictive value: 95.7%, negative predictive value: 95.8%).

CONCLUSIONS

Radiomics showed good diagnostic performance in differentiating PCP from other types of pneumonia in non-HIV patients. A combined diagnostic method including radiomics and serum β-D-glucan has the potential to provide an accurate and non-invasive way to identify the risk of PCP infection in non-HIV patients with CT manifestation of pneumonia.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT05701631).

Accuracy of Pneumocystis jirovecii Plasma Cell-Free DNA PCR for Noninvasive Diagnosis of Pneumocystis Pneumonia

Pneumocystis pneumonia (PCP) caused by Pneumocystis jirovecii is a serious infection in immunocompromised hosts which requires prompt diagnosis and treatment. The recommended specimen for diagnosis of PCP is bronchoalveolar lavage (BAL) fluid, which is invasive and may not be possible in unstable patients. The aim of this study was to evaluate the accuracy of noninvasive P. jirovecii plasma cell-free DNA (cfDNA) PCR using recently optimized preanalytical and analytical methods. Adult patients undergoing clinical testing for PCP with direct fluorescent antibody stain (DFA), respiratory PCR, and/or β-d-glucan were included in this study. Sensitivity and specificity P. jirovecii plasma cfDNA PCR was determined in PCP suspects categorized as proven and probable. A total of 149 patients were included in this study, of which 10 had proven and 27 had probable PCP. Most patients (95.9%, 143/149) were immunocompromised, including hematological malignancies (30.1%), bone marrow transplant (11.2%), solid organ transplantation (47.6%), and HIV/AIDS (4.2%). P. jirovecii plasma cfDNA PCR showed sensitivity and specificity of 100% (10/10; 95% confidence interval [CI], 69.2 to 100) and 93.4% (127/136; 95% CI, 87.8 to 96.9), and 48.6% (18/37; 95% CI, 31.9 to 65.6) and 99.1% (108/109; 95% CI, 94.9 to 100) in proven and proven/probable cases, respectively. P. jirovecii cell-free DNA PCR was similar in sensitivity but with substantially improved specificity over β-d-glucan (sensitivity, 60.0% [18/30; 95% CI, 40.6 to 77.3]); specificity, 66.7% [22/33; 95% CI, 48.2 to 82.0]) in patients with proven/probable PCP. Plasma cfDNA PCR offers a noninvasive testing option for early and accurate diagnosis of PCP, particularly in patients who cannot tolerate bronchoscopy.

Liquid Biopsy for Promising Non-invasive Diagnostic Biomarkers in Parasitic Infections

BACKGROUND

Liquid biopsy refers to the sampling and molecular analysis of body fluids such as blood, saliva, and urine in contrast to conventional tissue biopsies. Liquid biopsy approach can offer powerful non-invasive biomarkers (circulating markers) for diagnosis and monitoring treatment response of a variety of diseases, including parasitic infections.

METHODS

In this review, we concentrate on cell-free DNA (cfDNA), microRNA (miRNA), and exosomes in the published literature.

RESULTS

Considering the high prevalence and severity of parasitic infections worldwide, circulating biomarkers can provide a new insight into the diagnosis and prognosis of parasites in the near future. Moreover, identifying and characterizing parasite- or host-derived circulating markers are important for a better understanding of the pathogenesis of parasite infection and host-parasite relationship at the molecular level. Profiling of biomarkers for parasitic diseases is a promising potential field, though further studies and optimization strategies are required, both in vitro and in vivo.

CONCLUSION

In this review, we discuss three approaches in the liquid biopsy including circulating cfDNA, miRNAs, and exosomes for diagnosis and evaluation of parasites and summarize circulating biomarkers in non-invasive samples during parasitic infections.

Pneumocystis pneumonia and rheumatic disease: diagnostic potential of circulating microbial cell-free DNA sequencing

Objectives

The aim of this study was to explore the clinical utility of circulating microbial cell-free DNA (cfDNA) sequencing as a non-invasive approach for diagnosis of Pneumocystis jirovecii pneumonia (PJP) in immunocompromised patients with rheumatic disease (RD).

Methods

The study included 72 RD patients with suspected lung infections admitted to Renji hospital. Eighteen individuals were diagnosed with PJP, and 54 patients without PJP were enrolled as the control group. All patients had undergone pulmonary CT scans, and blood and respiratory tract specimens had been subjected to metagenomic next-generation sequencing (mNGS) and conventional microbiological tests. The clinical and laboratory parameters were collected, and the efficacy of circulating microbial cfDNA of P. jirovecii was evaluated.

Results

Of the 18 patients with PJP, the average age was 53.0 years, and the median time between RD diagnosis and PJP presentation was 126.0 days (interquartile range 84.0–176.3 days). Low circulating CD4⁺ cell counts and a lack of PJP prophylaxis were observed in the patients. Metagenomic NGS of circulating microbial cfDNA was performed in 69 patients, including 15 cases with PJP and 54 controls. Twelve (80%) of 15 analysed blood samples contained P. jirovecii sequences in the PJP group, with P. jirovecii not detected among controls. There was a significant difference between PJP and non-PJP groups (P < 0.001), with a sensitivity of 83.3% and specificity of 100% when using plasma cfDNA sequencing. Higher β-D-glucan levels were found in patients with positive results for P. jirovecii in plasma cfDNA sequencing.

Conclusion

Metagenomic NGS of circulating microbial cfDNA is a potential tool for diagnosis of PJP in RD patients.

Clinical Application of Metagenomic Next-Generation Sequencing in Patients with Hematologic Malignancies Suffering from Sepsis

Background: Sepsis remains a common but fatal complication among patients with immune suppression. We aimed to investigate the performance of metagenomic next-generation sequencing (mNGS) compared with standard microbiological diagnostics in patients with hematologic malignancies. Methods: We performed a prospective study from June 2019 to December 2019. Adult patients with hematologic malignancies and a clinical diagnosis of sepsis were enrolled. Conventional diagnostic methods included blood cultures, serum galactomannan for Aspergillus, cryptococcal antigen and cytomegalovirus (CMV) viral loads. Blood samples for mNGS were collected within 24 h after hypotension developed. Results: Of 24 patients enrolled, mNGS and conventional diagnostic methods (blood cultures, serology testing and virus RT-PCR) reached comparable positive results in 9 cases. Of ten patients, mNGS was able to identify additional pathogens compared with conventional methods; most of the pathogens were virus. Conclusion: Our results show that mNGS may serve as adjunctive diagnostic tool for the identification of pathogens of hematologic patients with clinically sepsis.

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

BACKGROUND

Pneumocystis jirovecii pneumonia (PCP) is an opportunistic infection commonly affecting immunocompromised people. Diagnosis usually requires invasive techniques to obtain respiratory specimens. Minimally invasive detection tests have been proposed, but their operating characteristics are poorly described.

OBJECTIVES

To systematically review and meta-analyse the performance of minimally invasive PCP detection tests to inform diagnostic algorithms.

DATA SOURCES

Medline, Embase, Cochrane Library (inception to 15 October 2020).

STUDY ELIGIBILITY CRITERIA

Studies of minimally invasive PCP detection tests were included if they contained a minimum of ten PCP cases.

PARTICIPANTS

Adults at risk of PCP.

TESTS

Non-invasive PCP detection tests.

REFERENCE STANDARD

Diagnosis using the combination of clinical and radiographical features with invasive sampling.

ASSESSMENT OF RISK BIAS

Using the QUADAS-2 tool.

METHODS

We used bivariate and, when necessary, univariate analysis models to estimate diagnostic test sensitivity and specificity.

RESULTS

Fifty-two studies were included; most studies (40) comprised exclusively human immunodeficiency virus (HIV) -infected individuals; nine were mixed (HIV and non-HIV), two were non-HIV and one study did not report HIV status. Sampling sites included induced sputum, nasopharyngeal aspirate, oral wash and blood. The four testing modalities evaluated were cytological staining, fluorescent antibody, PCR and lactate dehydrogenase. Induced sputum had the most data available; this modality was both highly sensitive at 99% (95% CI 51%-100%) and specific at 96% (95% CI 88%-99%). Induced sputum cytological staining had moderate sensitivity at 50% (95% CI 39%-61%) and high specificity at 100% (95% CI 100%-100%), as did fluorescent antibody testing with sensitivity 74% (95% CI 62%-87%) and specificity 100% (95% CI 91%-100%).

CONCLUSION

There are several promising minimally invasive PCP diagnostic tests available, some of which may reduce the need for invasive respiratory sampling. Understanding the operating characteristics of these tests can augment current diagnostic strategies and help establish a more confident clinical diagnosis of PCP. Further studies in non-HIV infected populations are needed.

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

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.

Rapid and sensitive identification of pleural and peritoneal infections by droplet digital PCR

Pleural and peritoneal infections cause substantial morbidity and mortality. Traditional diagnostic methods rely on the cultivation of clinical samples, which usually takes days to obtain report and holds a low detection sensitivity. In this study, we evaluated a 5-fluorescent-channel droplet digital PCR (ddPCR) system and 5 assay panels for culture-independent rapid pathogen detections directly from pleural and peritoneal fluid samples. Traditional culture of the same sample was used as reference. A total of 40 pleural fluid samples and 19 peritoneal fluid samples were tested in this study. Twenty-five positives including 4 polymicrobial infections by culture and 26 positives including 11 polymicrobial infections by ddPCR were detected for pleural fluid samples; 14 positives including 2 polymicrobial infections by culture and 15 positives including 3 polymicrobial infections by ddPCR were detected for peritoneal fluid samples. Klebsiella pneumoniae was the most common bacterium detected both in pleural and in peritoneal fluid samples. The sensitivity of the ddPCR assay for pleural and peritoneal fluid samples was 96% (95% confidence interval (CI) = 79.65 to 99.90%) and 92.86% (95% CI = 66.13 to 99.82%), respectively. The turnaround time of the ddPCR assay was approximately 3 h comparing with 38.30 ± 22.44 h for culture-based identifications. Our results demonstrated that the ddPCR assay is a rapid and sensitive method for identifying pathogens responsible for pleural and peritoneal infections and would be a promising approach for early diagnosis and optimizing treatment of infections.

Molecular diagnosis of Pneumocystis pneumonia in immunocompromised patients

PURPOSE OF REVIEW

Pneumocystis pneumonia (PCP) is a frequent opportunistic infection associated with a high mortality rate. PCP is of increasing importance in non-HIV immunocompromised patients, who present with severe respiratory distress with low fungal loads. Molecular detection of Pneumocystis in broncho-alveolar lavage (BAL) has become an important diagnostic tool, but quantitative PCR (qPCR) needs standardization.

RECENT FINDINGS

Despite a high negative predictive value, the positive predictive value of qPCR is moderate, as it also detects colonized patients. Attempts are made to set a cut-off value of qPCR to discriminate between PCP and colonization, or to use noninvasive samples or combined strategies to increase specificity.

SUMMARY

It is easy to set a qPCR cut-off for HIV-infected patients. In non-HIV IC patients, a gain in specificity could be obtained by combining strategies, that is, qPCR on BAL and a noninvasive sample, or qPCR and serum beta-1,3-D-glucan dosage.

Cell free DNA: revolution in molecular diagnostics - the journey so far

Cell free DNA (cf-DNA) refers to all non -ncapsulated DNA present in the blood stream which may originate from apoptotic cells as a part of the physiological cell turnover, or from cancer cells or fetal cells. Recent studies have highlighted the utility of cfDNA analysis for genetic profiling of cancer, non-invasive prenatal testing besides many other clinical applications. In our review we discuss the sources of cfDNA in the body, the techniques most commonly being used for its isolation and analysis, the applications of cfDNA testing and the associated pros-cons. We conclude that for prenatal testing, cfDNA analysis provides an effective, non-invasive and safer alternative to traditional amniocentesis and chorionic villus sampling tests. Also, in cancer patients, cfDNA analysis is useful for genetic profiling and follow-up during treatment. However, standardization of methods of isolation and analysis has become crucial for the success of widespread use of cfDNA analysis.

Pneumocystis jirovecii Pneumonia and Human Immunodeficiency Virus Co-Infection in Western Iran

BACKGROUND

The human immunodeficiency virus (HIV) is one of the greatest health challenges facing worldwide. The virus suppresses the immune system of the patient. The purpose of this study was to describe the epidemiology of Pneumocystis jirovecii colonization, rarely found in normal people, in patients with stage 4 HIV infection in Kermanshah, Iran, from Mar 1995 to Feb 2016.

METHODS

In this retrospective study, we surveyed medical records of stage 4 HIV-positive patients with Pneumocystis admitted to Behavioral Counseling Center of Kermanshah. Several parameters were analyzed including demographic characteristics, body mass index (BMI), treatment regimen, diagnostic methods, presenting signs and symptoms, presence of co-pathogens (bacteria, viruses, or fungi), and nadir of CD4 T-cell count before and after treatment.

RESULTS

During the study period, 114 HIV-positive patients were analyzed, of whom 93 were male and 21 were female, respectively. Of 114 cases, 26 (22.8%) patients had Pneumocystis. All 26 colonized patients had CD4 cell counts below 200 cells/mm3 (range 9-186). The median CD4 count increased from 91 cells/mm³ pre-trimethoprim/sulfamethoxazole (TMP/SMX) to an estimated 263 cells/mm³ after starting (TMP/SMX). BMI was normal in the majority of the patients (85%) and coughs, sputum, and chest pain (19; 73%) followed by dyspnea, weakness, and lethargy (7; 27%) were the most common presentations of fungal pneumonia.

CONCLUSION

HIV/AIDS-infected patients are an environmental reservoir of P. jirovecii infection that might transmit the infection from one person to another via the airborne route. In addition, rapid identification of such individuals may reduce the morbidity and mortality rate of this disease.

Investigation of Preanalytical Variables Impacting Pathogen Cell-Free DNA in Blood and Urine

Pathogen cell-free DNA (pcfDNA) in blood and urine is an attractive biomarker; however, the impact of preanalytical factors is not well understood. Blood and urine samples from healthy donors spiked with cfDNA from Mycobacterium tuberculosis, Salmonella enterica, Aspergillus fumigatus, and Epstein-Barr virus (EBV) and samples from tuberculosis patients were used to evaluate the impact of blood collection tube, urine preservative, processing delay, processing method, freezing and thawing, and sample volume on pcfDNA. The PCR cycle threshold (C_T ) was used to measure amplifiable cfDNA. In spiked samples, the median C_T values for M. tuberculosis, S. enterica, and EBV cfDNA were significantly lower in blood collected in K₂EDTA tubes than those in Streck and PAXgene blood collection tubes, and they were was significantly lower in urine preserved with EDTA (EDTA-urine) than in urine preserved with Streck reagent (Streck-urine). Blood and urine samples from TB patients preserved with K₂EDTA and Tris-EDTA, respectively, showed significantly lower median M. tuberculosis C_T values than with the Streck blood collection tube and Streck urine preservative. Processing delay increased the median pathogen C_T values for Streck and PAXgene but not K₂EDTA blood samples and for urine preserved with Streck reagent but not EDTA. Double-spin compared with single-spin plasma separation increased the median pathogen C_T regardless of blood collection tube. No differences were observed between whole urine and supernatant and between fresh and thawed plasma and urine after 24 weeks at -80°C. Larger plasma and urine volumes in contrived and patient samples showed a significantly lower median M. tuberculosis C_T These findings suggest that large-volume single-spin K₂EDTA-plasma and EDTA-whole urine with up to a 24-h processing delay may optimize pcfDNA detection.

Diagnosis of Pneumocystis pneumonia by real-time PCR in patients with various underlying diseases

BACKGROUND

Pneumocystis pneumonia (PCP) is a disease caused by the opportunistic infection of the fungus Pneumocystis jirovecii. Several PCR methods have been developed to aid in the diagnosis of PCP. In this study, we evaluated the performance of a real-time PCR in the diagnosis of PCP, in patients with various underlying diseases.

METHODS

Ninety-seven BAL samples and 94 sputum samples from 191 patients were used in the study. Patients were classified as PCP (121 patients) or non-PCP (70 patients) based on their clinical and radiological presentations.

RESULTS

Real time PCR amplified the P. jirovecii mitochondrial large-subunit rRNA gene with a detection limit of 68 copies of DNA per reaction. Non-PCP pathogens including 32 different fungi and bacteria were also evaluated. Overall, 71.9% of the samples from PCP patients and 14.5% of those from non-PCP patients were positive for the PCR test with a C_T value of the real-time PCR below 45. The main underlying diseases of the patients were hematological or solid malignancies (47.1%) and HIV infection (8.9%). The C_T values of the test were significantly lower in BAL samples from PCP patients than those from non-PCP patients (p = 0.024). No non-PCP patient had a C_T value below 30, whereas samples from 24.8% of PCP patients with underlying diseases had a C_T value below 30.

CONCLUSION

Since false positive PCR results were obtained, perhaps due to colonization, we suggest that the diagnosis of PCP should be based on a combination of clinical symptoms, underlying diseases, and PCR results.

Serum-based diagnosis of Pneumocystis pneumonia by detection of Pneumocystis jirovecii DNA and 1,3-β-D-glucan in HIV-infected patients: a retrospective case control study

BACKGROUND

Pneumocystis jirovecii pneumonia (PCP) is one of the most common HIV-related opportunistic infections. The diagnosis of PCP is based on analyses from respiratory tract specimens which may require the invasive procedure of a diagnostic bronchoscopy. The objective of this study was to evaluate the diagnostic potential of Pneumocystis jirovecii PCR in serum combined with the 1,3-β-D-glucan (betaglucan) test for the diagnosis of PCP in HIV-infected patients.

METHODS

This was a retrospective case-control study including serum samples from 26 HIV-infected patients with PCP collected within 5 days prior to the start of PCP treatment, 21 HIV-infected control subjects matched by blood CD4⁺ cell counts, and 18 blood donors. The serum samples were analyzed for Pneumocystis jirovecii PCR and betaglucan. The reference standard for PCP was based on previously described microbiological and clinical criteria.

RESULTS

All patients with PCP had detectabe Pneumocystis jirovecii DNA in serum yielding a sensitivity for the Pneumocystis jirovecii PCR assay in serum of 100%. All blood donors had negative Pneumocystis PCR in serum. The specificity when testing HIV-infected patients was 71%, but with a PCR Cycle threshold (Ct) value of 34 as cut-off the specificity was 90%. At a putative pretest probaility of 20%, the negative and positive predictive value for the Pneumocystis PCR assay in serum was 0.99 and 0.71, respectively. Betaglucan with cut-off level 200 pg/ml combined with a positive Pneumocystis jirovecii PCR result had sensitivity and specificity of 92 and 90%, respectively. The concentration of Pneumocystis jirovecii DNA in serum samples, expressed by the PCR Ct values, correlated inversely to the betaglucan levels in serum.

CONCLUSION

In this case-control study including 70% of all HIV-infected patients with PCP treated at Sahlgrenska University Hospital during a time period of 13 years, Pneumocystis PCR analysis on serum samples had a very high sensitivity and negative predictive value for the diagnosis of PCP in HIV-infected patients. A serum-based diagnostic procedure either based on Pneumocystis jirovecii PCR alone or in combination with betaglucan analysis may thus be feasible and would facilitate the care of HIV-infected patients with suspected PCP.

Non-culture based assays for the detection of fungal pathogens

Traditional, culture based methods for the diagnosis of fungal infections are still considered as gold standard, but they are time consuming and low sensitive. Therefore, in order to overcome the limitations, many researchers have focused on the development of new immunological and molecular based rapid assays that could enable early diagnosis of infection and accurate identification of fungal pathogens causing superficial and invasive infection. In this brief review, we highlighted the advantages and disadvantages of conventional diagnostic methods and possibility of non-culture based assays in diagnosis of superficial fungal infections and presented the overview on currently available immunochromatographic assays as well as availability of biomarkers detection by immunodiagnostic procedures in prompt and accurate diagnosis of invasive fungal infections. In addition, we presented diagnostic efficiency of currently available molecular panels and researches in this area.