Evaluation of a new diagnostic method for quantification of EBV and HHV-6 viral load in bronchoalveolar lavage

BACKGROUND: Epstein-Barr virus (EBV) and human herpesvirus 6 (HHV-6) are frequently detected in bronchoalveolar lavage (BAL). The quantification and interpretation of viral loads on BAL represent one of the limits to determine their effective pathogenetic role. Thus, we investigated whether the normalization of the viral load for the cellularity of the recovered fluid in a population of patients with pneumonia was correlated with clinical outcome. METHODS: We conducted a retrospective analysis of BAL samples with a reverse transcriptase-polymerase chain reaction positivity for EBV and/or HHV-6 in patients with bacterial or viral pneumonia. We performed a quantitative analysis for EBV and HHV-6, and then we applied a normalization of viral copies per 500,000 cells, using a mathematical equation. RESULTS: We included 65 samples with 78% and 51% positivity for EBV and HHV-6 respectively. The viral concentration significantly changed after the normalization both for EBV and HHV-6 (P<0.05). We observed different correlation among standard and normalized viral loads for management of steroid and antiviral therapies. CONCLUSIONS: This study shows how normalization of viral load for the cellularity of recovered fluid could change interpretation of viral concentration on BAL. Differences in management of therapies based of BAL results suggest that quantification of cellularity could be crucial for a correct clinical judgment.