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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:

Thank you !!

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