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Comparative Analysis of viral Load in
RSV Bronchiolitis
21/10/2015
Inbal Golan Tripto
Pediatric Pulmonology Unit
Soroka University Medical Center
Beer- Sheva
Background
• Respiratory Syncytial Virus (RSV) is the leading pathogen for acute bronchiolitis 1
• Single stranded RNA
• Two subtypes : A and B
1 Hall CB. N Engl J Med. 2001
Background
• Variable laboratory diagnostic methods :
Cell tissue culture - gold standard
Rapid antigen based assays - enzyme linked immunoassays
Indirect and direct immunofluorescent
molecular assays – RT- PCR
viral load - Cell culture and quantitative RT-PCR
Objective :
• To investigate the viral load of infants with RSV bronchiolitis
in comparative analysis:
Two different media (VCM vs. UTM)
nasal swab vs. nasal wash
PCR vs. culture
• To investigate the correlation between viral load and disease severity
Methods : study design
• A prospective cohort study : November 2014 to February 2015
• Age <1 y, Clinical diagnosis of acute bronchiolitis
• Exclusion criteria: previous respiratory admission, chromosomal abnormality, chronic heart or lung disease
• RSV identification in nasal wash was done using rapid immunochromatographic assay
Virology
• 2 nasal swabs and 2 nasal wash were collected twice from each infant (at admission and 48 hours later)
• collection tubes containing different media UTM or VCM
• All samples were stored at -80°c and tested at ViroclinicsBiosciences in Netherlands
• Viral load was determined by Quantitative RT-PCR and by quantitative virus culture - TCID50*
* TCID50 – Tissue Culture infective dose
Results :
• 100 samples were collected from 13 infants
• 12 patients were RSV-A positive and one was RSV-B positive
• no double infection was observed
%nDemographic Characteristics
100%13Total Subjects
46%6Male
77%10Bedouin
15%21st degree with Asthma
54%7Smoker at Home
Demographics & Clinical DataS.DMeanMedianPersonal Information
3.85.76Age (months)
237.738Gestational age (weeks)
1.14.24day of illness
%nTreatment
100%13O2 support
30%4Bronchodilators
0%noneSteroids (inhaled)
0%noneSteroids (systemic)
46%6Antibiotics
S.D.MeanMedian
27.43933O2 support (hours)
23.266.365.5LOS (hours)
Correlation : UTM vs. VCM
p-value 95% CI Spearman's rho
(two tailed)
Viral Load Test
<0.0010.49 – 0.980.85Nose Swab 1 culture
<0.0010.76 – 0.990.94Nose Swab 2 culture
<0.0010.53- 0.980.87Nose Swab 1, PCR
<0.0010.55 – 0.990.92Nose Swab 2, PCR
0.0010.46 – 0.940.8Nose Wash 1 culture
0.020.34 – 0.980.8Nose Wash 2 culture
<0.0010.76 – 10.96Nose Wash 1, PCR
<0.0010.48 – 0.990.86Nose Wash 2, PCR
Correlation : UTM vs. VCM
Correlation : Swab vs. Wash
p-value 95% CI Spermans' rho (two tailed)Viral Load Test
0.020.12 - 0.890.621'st culture UTM
0.020.17 - 0.960.621'st culture VCM
<0.0010.63 - 0.840.882'nd culture UTM
0.0010.47 - 0.970.842'nd culture VCM
0.030.28 - 0.950.61'st PCR UTM
0.030.1 - 0.850.611'st PCR VCM
0.10.2 - 0.850.482'nd PCR UTM
0.020.15 - 0.930.682'nd PCR VCM
Correlation : Swab vs. Wash
Viral Load in nose swab & wash
Viral Load in Culture & PCR
Correlation with disease severity
p-value Spermans' rho
(two tailed)
Viral Load Test
0.74-0.11st Nose Swab PCR UTM vs. O2 Support
0.720.121’st Nose Swab PCR UTM vs. LOS
* Results are NOT Statistically Significant
Viral load per day of illness
DeVincenzo et al, NEJM 2014
Discussion
• Different transport media were correlated, UTM vs. VCM
• Nasal swab and wash were correlated, although signals were
higher in wash
• RT-PCR and virus cultures were comparable
• No significant correlation between Viral Load and clinical severity
• Limitations
• Nasal swabs were as good as nasal washes
• Nasal swabs are much easier to use, less traumatic for the patient and time consuming
• Nasal swabs are independent on the amount of NACL usually used in nasal wash
• Viral load was not correlated to time of O2 support & LOS
Conclusion:
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