Clinical correlation of influenza and respiratory syncytial virus load measured by digital PCR

Abstract

Acute respiratory tract infections are a major cause of respiratory morbidity and mortality in pediatric patients worldwide. However, accurate viral and immunologic markers to predict clinical outcomes of this patient population are still lacking. Droplet digital PCR assays for influenza and respiratory syncytial virus (RSV) were designed and performed in 64 respiratory samples from 23 patients with influenza virus infection and 73 samples from 19 patients with RSV infection. Samples of patients with hematologic malignancies, solid tumors, or sickle cell disease were included. Clinical information from institutional medical records was reviewed to assess disease severity. Samples from patients with fever or respiratory symptoms had a significantly higher viral loads than those from asymptomatic patients. Samples from patients with influenza virus and RSV infection collected at presentation had significantly higher viral loads than those collected from patients after completing a course of oseltamivir or ribavirin, respectively. RSV loads correlated positively with clinical symptoms in patients ≤5 years of age, whereas influenza viral loads were associated with clinical symptoms, irrespective of age. Patients receiving antivirals for influenza and RSV had a significant reduction in viral loads after completing therapy. Digital PCR offers an effective method to monitor the efficacy of antiviral treatment for respiratory tract infections in immunocompromised hosts.

Pushing beyond specifications: Evaluation of linearity and clinical performance of the cobas 6800/8800 SARS-CoV-2 RT-PCR assay for reliable quantification in blood and other materials outside recommendations

“…Diagnostic RT-PCR was quickly determined as the gold standard for detecting the new pathogen in patients, in large part due to the rapid dissemination of complete virus sequences from the assumed origin of the outbreak in China and consecutive publication of specific PCR assays [ 3 , 4 ]. Besides merely confirming the diagnosis, there exists evidence for a correlation between viral loads and clinical outcomes for various respiratory viruses, including Influenza and the original SARS-CoV [ 5 , 6 ]. In the case of SARS-CoV-2 there has already been a flurry of publications describing viral load dynamics in different clinical specimens [ 7 , 8 ].…”

COVID-19 Infection

“…The determinants of these varied outcomes remain unknown, but experience with other viruses suggests that variation in the dose of viral inoculum, route of inoculation, and underlying immune status of the patient can lead to widely variable host responses. 36 Higher viral loads on random sampling identified individuals with greater symptom burden in influenza 37 and greater mortality in adenoviral pneumonia. 38 At the same time, moderate SARS-CoV-2 viral loads can be detected in nasal swabs up to 2 weeks after the onset of symptoms and in asymptomatic individuals.…”

A six‐plex droplet digital RT‐PCR assay for seasonal influenza virus typing, subtyping, and lineage determination

“…Results from recent clinical studies indicate that influenza virus load can be a marker for disease severity. 9 Influenza A and B viruses are often detected and quantified by qRT-PCR in modern clinical settings. 7 However, while this diagnostic approach is highly robust, qRT-PCR is sensitive to inhibitors in clinical samples and absolute quantification of its target(s) is highly reliant on accuracy of the standard curve(s), resulting in significant inter-laboratory variations.…”

“…7 Viral loads determined by qRT-PCR assays are suggested to be useful markers for assessing disease severity and for predicting clinical outcomes. [8][9][10] However, quantification of nucleic acid targets in standard qRT-PCR assays heavily relies on the quality of external standards and the relative signal-to-noise ratio. 11,12 Thus, the performance, reproducibility, and amplification efficiency of a standard qRT-PCR-based assay can vary greatly between different laboratories.…”