Matti Waris (Finland)
University of Turku and Clinical Microbiology, Turku University Hospital, Finland Institute of BiomedicineAuthor Of 2 Presentations
IMPACT OF RESPIRATORY PATHOGEN PCR CYCLE THRESHOLD VALUE ON THE CLINICAL SEVERITY OF INFECTION IN ACUTELY ILL CHILDREN
Abstract
Backgrounds:
The polymerase chain reaction (PCR) cycle threshold (Ct) value represents the number of amplification cycles required to yield a positive test result and inversely correlates with pathogen load. Here, we evaluated whether Ct values of respiratory pathogens were associated with the clinical severity of infections in acutely ill children.
Methods
In this cross-sectional study at a pediatric emergency department, we obtained nasopharyngeal swabs from 800 children with fever or respiratory symptoms. Samples were analyzed for 21 respiratory pathogens using point-of-care multiplex-PCR device (Qiastat). We compared Ct values in children who needed hospitalization and those who were discharged from ED using a multivariate logistic regression model adjusted for age and sex. In addition, the association of Ct values with CRP values was analyzed with linear regression.
Results:
Of the 800 participants, 356 (45 %) were girls. The median age was 3.0 years. At least one pathogen was detected in 594 (74 %) participants. The most common pathogen was picornavirus, i.e. rhinovirus or enterovirus (328, 41 %) followed by RSV (133, 17 %). In total, 334 (42 %) patients were hospitalized, ranging from 11 % (3/27) for those with influenza A to 61 % (81/133) for those with RSV infection (Figure). When adjusted for age and sex, no statistically significant associations between Ct-value and need for hospitalization were found for any pathogen. In participants with detection of rhino/enterovirus, high Ct-value, i.e. low viral load, associated with high CRP value (β coefficient 2.51 [95 % CI 0.79 to 4.22]).
Conclusions/Learning Points:
Viral or pathogen load, estimated by PCR cycle threshold values, was not associated with the need for hospitalization due to respiratory viral infection in children. Thus, the clinical utility of Ct-values appears to be limited.
MYXOVIRUS RESISTANCE PROTEIN A FOR DISCRIMINATING BETWEEN VIRAL AND BACTERIAL LOWER RESPIRATORY TRACT INFECTIONS IN CHILDREN – THE TREND STUDY
Abstract
Backgrounds:
Discriminating between viral and bacterial lower respiratory tract infection (LRTI) in children is challenging, leading to an excessive use of antibiotics. Myxovirus resistance protein A (MxA) is a promising biomarker for viral infections. The aim of the study was to assess the difference in blood MxA levels between children with viral and bacterial LRTI and to assess MxA levels in relation to specific respiratory viruses.
Methods
Children with lower respiratory tract infection (LRTI) were enrolled as cases at Sachs’ Children and Youth Hospital, Stockholm, Sweden. Nasopharyngeal aspirates (for respiratory PCR analysis) and blood samples (for analysis of MxA and CRP) were systematically collected from all study subjects in addition to standard laboratory/radiology assessment. Aetiology was defined according to an algorithm based on laboratory and radiological findings. The diagnostic accuracy of MxA was assessed by calculating sensitivity, specificity and area under the curve (AUC) in receiving operator characterstic (ROC) curves.
Results:
Of the 326 cases, 242 had viral aetiology, 11 had mixed viral-bacterial aetiology, 5 had bacterial aetiology, 2 had atypical bacterial aetiology, and 66 cases had undetermined aetiology. MxA levels were higher in children with viral LRTI as compared with bacterial LRTI (p<0.01, AUC 0.92). In the subgroup of children with pneumonia diagnosis, a cut-off of MxA 430µg/l discriminated between viral and bacterial aetiology with 93% sensitivity and 100% specificity (AUC 0.98). The highest MxA levels were seen in cases PCR positive for adenovirus and respiratory syncytial virus (median MxA 1961µg/l and 1226µg/l respectively).
Conclusions/Learning Points:
MxA accurately discriminated between viral and bacterial etiology in children with LRTI, in particular in the group of children with pneumonia diagnosis. Thus, MxA determination might improve rational use of antibiotics in this patient group.