DiFei Academic | mNGS has high diagnostic value in PJP infection in patients with dermatomyositis

Introduction

Recently, the team from the Department of Rheumatology and Immunology of China-Japan Friendship Hospital cooperated with Difei Medical toRheumatology(IF=7.064) published 'High prevalence and mortality of Pneumocystis jirovecii pneumonia in anti-MDA5 antibody-positive dermatomyositis'.The article combines Pneumocystis jiroveci with anti-MDA5+ dermatomyositis (Antimelanoma differentiation-assosicated gene 5 antibody-positive dermatomyositis, anti-MDA5+ DM) P. jirovecii (PJP) infected patients underwent metagenomic next-generation sequencing (mNGS) and real-time fluorescence quantitative PCR detection.The high prevalence and mortality of anti-MDA5+ DM combined with PJP infection were discussed, and the diagnostic value of mNGS sequencing in detecting PJP infection in anti-MDA5+ DM was confirmed.

/ Research Background /

PJP is a common opportunistic infectious agent that can cause pneumonia in immunocompromised populations with human immunodeficiency virus (HIV) infection (HIV), malignancy, and underlying autoimmune rheumatic disease (ARD).The onset of PJP in non-HIV immunodeficient people is more insidious, rapid, and more prone to mixed infections, and its mortality rate is as high as 35-55%.MDA5+ DM is a rare but highly fatal autoimmune disease whose clinical manifestations include skin and muscle symptoms, lymphopenia, and interstitial lung disease (ILD).Some studies have pointed out that the mortality rate of PJP in patients with DM is higher than that in patients with other rheumatic diseases.Given the high mortality rate of PJP in DM patients, rapid and accurate pathogen diagnosis is crucial to guide anti-infective treatment and improve patient prognosis.

PJP is somewhat resistant to traditional culture methods, while immunofluorescence microscopy and serum (1,3)-β-D-glucan (BDG) methods have low sensitivity and positive rate.Although PCR is a rapid and highly sensitive method for detecting pathogenic microorganisms, its diagnostic value is limited in mixed infections that are common in immunosuppressed patients.

In recent years, mNGS pathogenic microorganism identification technology has been widely recognized and applied clinically, and has significant advantages in rapid, comprehensive, and unbiased diagnosis of mixed infection pathogens in immunosuppressed patients.Previously, a large number of studies have reported the efficacy of mNGS in diagnosing PJP infection in patients with organ transplantation, hematological malignancies and solid tumors, but few studies have reportedmNGSDiagnostic value in anti-MDA5+ DM combined with PJP infection.

Therefore, this study aimed to: (1) determine the risk factors and prognostic factors of PJP infection in patients with anti-MDA5+ DM; (2) analyze and compare the pathogen diagnosis effect and time consumption of mNGS and conventional methods; (3) evaluate the effectiveness of mNGS in anti-MAD5+ DM Detection performance of mixed infections in patients.

/ Research methods /

This retrospective study consecutively included anti-MDA5+ DM patients in the rheumatology department of this hospital from January 2016 to July 2022.In this study, patients were grouped into PJP+ group or PJP- group, and the patient's background, laboratory test indicators, clinical manifestations, treatment plan, and follow-up status were recorded in detail.

Laboratory tests include lymphocyte count, CD4+ T cell count, albumin (ALB), serum ferritin (FET), erythrocyte sedimentation rate (ESR), reactive protein (CRP), lactate dehydrogenase (LDH), BDG, and serum Electrolytes.Radiological examination includes ground glass opacities (GGO), consolidations, and cysts, and chest CT examination for the presence of ILD and rapidly progressive interstitial lung disease (RPILD).Patient treatment parameters included daily doses of glucocorticoids (GCs), pulse methylprednisolone therapy (PMT), immunosuppressants, and intravenous immune globulin (IVIG).PJP prophylaxis is defined as trimethoprim-sulfamethoxazole (TMP/SMZ) treatment for more than 1 month in patients who have not yet been diagnosed with PJP.所All patientsPerform alveolar lavage, lungbubble lavage solution(BALF）进Line PCR or mNGS detectionPJP。

/ Research result /

1. Clinical characteristics and risk factors of PJP in patients with anti-MAD5+ DM

A total of 91 anti-MDA5+ DM patients were included in this study, including 44 PJP+ and 47 PJP- patients. The detection rate of PJP in anti-MDA5+ DM was 48.4% (44/91); RPILD was more common in the PJP+ group (81.8% vs. 53.2%, p=0.004), fever (77.3% vs. 42.6%,p=0.001), hyponatremia (36.4% vs.8.5%, p=0.001) and BDG test positive (29.5% vs. 12.8%, p=0.049).

In addition, LDH in the PJP+ group (353.5 vs. 285.0 IU/L, p<0.001), CRP (0.58vs.0.30 mg/dl, p<0.001), ESR (29vs.20mm/h, p=0.027) and FET (1086.5vs.488.6 ng/ml, p=0.001) were significantly higher than those in the PJP- group.Finally, a logistic regression model was used and included in the comparisonp<0.05 factors and clinically significant factors, fever was found (OR=4.803, p=0.018) and elevated LDH levels (OR=1.008, p=0.028) is an independent risk factor for the occurrence of PJP, while TMP/SMZ prevention (OR=0.075, p=0.005) was identified as an independent protective factor (Figure 1).

Figure 1 Multiple logistic regression analysis of independent correlations in patients with anti-MDA5+ DM combined with PJP.

2. PJP mortality in anti-MDA5+ DM

Among patients with anti-MDA5+ DM, the 6-month mortality rate in the PJP+ group was higher than that in the PJP- group (34.1% vs. 4.3%, p<0.001).Compared with non-infected persons, PJP+ patients were more likely to develop respiratory failure (40.9% vs. 12.8%, p=0.002) and admission to ICU (22.7%vs.2.1%, p=0.003).In multivariate analysis, old age (HR=1.079, p=0.014) and high LDH value (HR=1.006, p<0.001) was finally confirmed to be an independent risk factor (Figure 2).

Figure 2 ResistanceMDA5+ DMmergeMultivariate Cox regression analysis of risk of death in patients with PJP

3. Comparison of BALF-mNGS and conventional diagnostic methods

This study compared the diagnostic performance of mNGS with PCR, LDH combined with serum BDG detection (LDH + BDG) (Table 2).A total of 62 patients completed all tests, including 22 patients in the PJP+ group and 40 patients in the PJP- group.The detection sensitivity of mNGS was higher than that of PCR (100.0% vs18.2%) and LDH+BDG (100.0% vs63.6%).mNGS showed good specificity similar to PCR (90.0% vs. 100.0%).The positive predictive value (PPV) of mNGS was 84.6% and the negative predictive value (NPV) was 100.0%, which was better than LDH + BDG detection.Through ROC analysis, mNGS has the highest AUC of 0.95 (p<0.001) (Figure 3A).BALF-mNGS has significant advantages in the diagnosis of PJP.The average detection time of mNGS was 30.58±10.79 h, which was significantly shorter than PCR (64.06±38.23 h; p<0.001) (Figure 3B).

Table 2 Comparison of diagnostic performance of mNGS, real-time fluorescence quantitative PCR and LDH+BDG

image 3 Competing with different detection methodsMDA5+ DM mergeDiagnostic performance of PJP infection

4. Detection performance of mNGS in mixed infection in patients with anti-MDA5+ DM

Among the 44 patients in the PJP+ group, 23 underwent mNGS testing.All 47 patients in the PJP-group underwent mNGS testing.The BALF-mNGS detection of pathogenic bacteria contents in the two groups is shown in Figure 4.In the PJP+ group, 30.4% of patients were infected with Pneumocystis jiroveci, and the remaining 69.6% were infected with Pneumocystis jiroveci combined with other pathogenic bacteria.In patients with anti-MDA5+ DM, infections are mainly caused by Gram-positive bacteria and Gram-negative bacteria, followed by various fungi, viruses, and Mycobacterium tuberculosis (MTB).

Figure 4 For two groups抗MDA5+ Distribution of pathogenic bacteria detected by mNGS in patients with DM

/ Summarize /

1. PJP in anti-MDA5+ DM patients have high morbidity and mortality.

2. Fever and elevated serum LDH are independent risk factors for the occurrence of PJP, and TMP/SMZ prevention is an independent protective factor for the occurrence of PJP.

3. Old age and elevated serum LDH are predictive factors for mortality in patients with anti-MDA5+ DM combined with PJP infection.

4. Clinicians’ ability to identify high-risk patients and promptly implement TMP/SMZ is crucial to preventing PJP.whenWhen PJP infection is suspected, mNGS is the preferred pathogen detection method for anti-MDA5+ DM.