RESUMO
BACKGROUND: Early diagnosis of congenital CMV infection (cCMVI) allows for early intervention and follow-up to detect delayed hearing loss. While CMV PCR in urine is the gold standard for cCMVI diagnosis, saliva testing is often performed. OBJECTIVES: Our aim was to determine (i) if swab saliva sampling needed standardization, (ii) if a threshold value in "virus copies per million cells (Mc)" in saliva samples could improve clinical specificity, and (iii) to establish a correlation between viral load in saliva and symptomatology/outcome of cCMVI. MATERIALS AND METHODS: In our institution, universal newborn screening is performed on saliva swabs at delivery or until day 3 of life. If positive, CMV PCR in urine is done within 2 weeks to confirm or exclude cCMVI. RESULTS: Cell quantification showed that saliva swab sampling was well performed as 95.4 % samples had more than 100 cells/10 µL. There was a good correlation between saliva viral load in copies/mL and in copies/Mc (Pearson's r = 0.96, p < 0.0001). However, threshold values, established to determine a viral load level at which we could confidently identify infected newborns, did not improve positive predictive value (21.8 % for copies/mL and 21 % for copies/Mc vs 25.4 % without threshold) but instead reduced sensitivity (88 % and 85% vs 100 % without threshold). Samples collected on day 2 or 3 had better positive predictive value (38.7 %) compared to those collected on day 1 (23.8 %). Symptomatology at birth was not significantly associated with viral load in saliva at diagnosis. However, sequelae occurrence was associated with viral load in saliva (copies/Mc). DISCUSSION: Our results confirm that saliva swab is a suitable sample for universal neonatal screening. However, identifying newborns that will develop sequelae remains an issue in the management of cCMVI.
RESUMO
BACKGROUND: Diagnosis of hepatitis C virus (HCV) infection and treatment monitoring rely on detection/quantification of HCV RNA and real-time polymerase chain reaction (PCR) techniques are expected to equivalently quantify the different HCV genotypes. OBJECTIVE: The clinical performance of the VERIS HCV assay for HCV RNA quantification was compared to that of the Abbott RealTime HCV assay. STUDY DESIGN: Qualitative concordance and quantitative comparison were evaluated on a first panel of 286 clinical samples containing HCV genotypes 1-6. Forty additional genotype 4 samples were tested to explore genotype 4 HCV RNA underquantification. RESULTS: Qualitative discrepancies were observed for low viral loads (<2 log10 IU/mL) in patients under antiviral therapy and would not have had any impact on patients' management with the current guidelines for the monitoring of patients on direct-acting antivirals (DAAs). Quantification results were well correlated (R2=0.89) with an overall minimal quantification bias (mean VERIS - Abbott difference) of -0.09 log10 IU/mL. Quantification agreement for genotypes 1, 2 and 3 samples was excellent, but reached -0.57 log10 IU/mL for 46 genotype 4 samples. A lower quantification bias of -0.24 log10 IU/mL was observed when testing 40 additional genotype 4 samples with a second reagent lot. Underquantification was not associated with 5' untranslated region (UTR) sequence polymorphisms but could be explained by 5' UTR RNA molecular modeling. CONCLUSION: HCV RNA quantification by the VERIS HCV assay and the Abbott RealTime HCV assay was well correlated for all HCV genotypes, except genotype 4 where 5' UTR RNA folding may impact quantification. Nevertheless, this underestimation of HCV RNA levels had no impact on clinical use.