Viral Detection by Reverse Transcriptase Polymerase Chain Reaction in Upper Respiratory Tract and Metagenomic RNA Sequencing in Lower Respiratory Tract in Critically Ill Children With Suspected Lower Respiratory Tract Infection

OBJECTIVES

Viral lower respiratory tract infection (vLRTI) contributes to substantial morbidity and mortality in children. Diagnosis is typically confirmed by reverse transcriptase polymerase chain reaction (RT-PCR) of nasopharyngeal specimens in hospitalized patients; however, it is unknown whether nasopharyngeal detection accurately reflects presence of virus in the lower respiratory tract (LRT). This study evaluates agreement between viral detection from nasopharyngeal specimens by RT-PCR compared with metagenomic next-generation RNA sequencing (RNA-Seq) from tracheal aspirates (TAs).

DESIGN

This is an analysis of of a seven-center prospective cohort study.

SETTING

Seven PICUs within academic children's hospitals in the United States.

PATIENTS

Critically ill children (from 1 mo to 18 yr) who required mechanical ventilation via endotracheal tube for greater than or equal to 72 hours.

INTERVENTIONS

We evaluated agreement in viral detection between paired upper and LRT samples. Results of clinical nasopharyngeal RT-PCR were compared with TA RNA-Seq. Positive and negative predictive agreement and Cohen's Kappa were used to assess agreement.

MEASUREMENTS AND MAIN RESULTS

Of 295 subjects with paired testing available, 200 (68%) and 210 (71%) had positive viral testing by RT-PCR from nasopharyngeal and RNA-Seq from TA samples, respectively; 184 (62%) were positive by both nasopharyngeal RT-PCR and TA RNA-Seq for a virus, and 69 (23%) were negative by both methods. Nasopharyngeal RT-PCR detected the most abundant virus identified by RNA-Seq in 92.4% of subjects. Among the most frequent viruses detected, respiratory syncytial virus demonstrated the highest degree of concordance (κ = 0.89; 95% CI, 0.83-0.94), whereas rhinovirus/enterovirus demonstrated lower concordance (κ = 0.55; 95% CI, 0.44-0.66). Nasopharyngeal PCR was more likely to detect multiple viruses than TA RNA-Seq (54 [18.3%] vs 24 [8.1%], p ≤ 0.001).

CONCLUSIONS

Viral nucleic acid detection in the upper versus LRT reveals good overall agreement, but concordance depends on the virus. Further studies are indicated to determine the utility of LRT sampling or the use of RNA-Seq to determine LRTI etiology.

Inhaled Nitric Oxide for the Treatment of Acute Bronchiolitis: A Multicenter Randomized Controlled Clinical Trial to Evaluate Dose Response

Rationale: Inhaled nitric oxide (iNO) has potential antiinflammatory, antimicrobial, and antiviral properties for patients with lower respiratory tract infections. Objectives: We compared the safety and efficacy of iNO administered in two concentrations in addition to standard supportive treatment (SST) compared with SST alone with the aim of improving clinical outcomes of infants with bronchiolitis. Methods: In this prospective, multicenter, double-blind, randomized controlled study, 89 infants hospitalized with moderate to severe bronchiolitis were randomly assigned to three treatment groups: 150 ppm NO plus SST (group 1), 85 ppm NO plus SST (group 2), and the control treatment (O₂/air plus SST) (group 3). Treatment was given for 40 minutes, four times each day, for up to 5 days. The primary endpoint was time to reach "fit for discharge." This was a composite endpoint composed of both reaching a sustained oxygen saturation ≥92% on room air and reaching a clinical score ⩽5. Secondary endpoints included time to reach sustained oxygen saturation ≥92% on room air, time to clinical score ⩽5, and time to hospital discharge. Safety was assessed by the number of treatment-related adverse events (AEs) or serious AEs. Time-to-event efficacy outcomes were analyzed using a Cox proportional hazards regression model. Hazard ratios (HR) describe how many times more likely an individual is to experience an event, if such an individual receives NO rather than the control treatment during the observational period. Results: Group 1 demonstrated significant efficacy for time to reach fit to discharge compared with groups 2 (HR, 2.11; P = 0.041) and 3 (HR, 2.32; P = 0.049). Group 1 also demonstrated significant efficacy for time to hospital discharge compared with groups 2 (HR, 2.01; P = 0.046) and 3 (HR, 2.28; P = 0.043). No significant differences were observed between groups 2 and 3 for either endpoint. There were no differences between treatment groups in time to reach a clinical score ⩽5. The iNO therapy was well tolerated, with no treatment-related serious AEs. Conclusions: Treatment with high-dose intermittent iNO at 150 ppm showed reduced time to clinical improvement compared with 85 ppm or control treatment of hospitalized infants with acute bronchiolitis. The 150-ppm iNO dose is well tolerated, with significant benefit compared with both standard therapy and 85 ppm iNO, improving respiratory outcomes and reducing length of stay. Clinical trial registered with www.clinicaltrials.gov (NCT04060979).

The Influence of the Microbiome on Early-Life Severe Viral Lower Respiratory Infections and Asthma-Food for Thought?

Severe viral lower respiratory infections are a major cause of infant morbidity. In developing countries, respiratory syncytial virus (RSV)-bronchiolitis induces significant mortality, whereas in developed nations the disease represents a major risk factor for subsequent asthma. Susceptibility to severe RSV-bronchiolitis is governed by gene-environmental interactions that affect the host response to RSV infection. Emerging evidence suggests that the excessive inflammatory response and ensuing immunopathology, typically as a consequence of insufficient immunoregulation, leads to long-term changes in immune cells and structural cells that render the host susceptible to subsequent environmental incursions. Thus, the initial host response to RSV may represent a tipping point in the balance between long-term respiratory health or chronic disease (e.g., asthma). The composition and diversity of the microbiota, which in humans stabilizes in the first year of life, critically affects the development and function of the immune system. Hence, perturbations to the maternal and/or infant microbiota are likely to have a profound impact on the host response to RSV and susceptibility to childhood asthma. Here, we review recent insights describing the effects of the microbiota on immune system homeostasis and respiratory disease and discuss the environmental factors that promote microbial dysbiosis in infancy. Ultimately, this knowledge will be harnessed for the prevention and treatment of severe viral bronchiolitis as a strategy to prevent the onset and development of asthma.