Evaluation of semi-quantitative results of the CMV DBS-test

BRIEF INTRODUCTION Quantification of CMV-DNA may identify children at higher risk of late sequelae of congenital CMV infection (cCMV). In this study we investigated the relation between semi-quantitative and quantitative results obtained in testing neonatal DBS, in the aim of using the CMV DBS-test for a preliminary formulation of prognosis. MATERIALS AND METHODS DBS of 232 newborns with isolation confirmed cCMV were analyzed by means of: a) DBS-test (Barbi et al., 2006). DNA purification: thermal shock. Amplification: nested-PCR (target: gB gene). Positive results were distinguished in “weak” (with 1/3 positive tests) and “strong” (at least 2/3). b) Quantitative Real-time PCR, “Q-CMV Real-time Complete Kit”, Nanogen (MIEA gene). DNA extraction: “QIAamp DNA Mini-kit” (QIAGEN). Clinical data available for 148 children at birth and follow-up were correlated to the semi-quantitative results. CLINICAL CASES OR SUMMARY RESULTS DBS-test results were “strong” in 197 cases, “weak” in 32 and negative in 3. Real-time PCR was positive in 184 cases (mean: 9,228; median: 1,278, range: 9-897,876 copies/ml) and negative in 48. “Strong” cases had median viral loads higher than “weak” cases (1,447 vs 702 copies/ml; Mann-Whitney’s Test, p<0.01). Babies symptomatic at birth were 30% in the “weak” group and 51% in the “strong” one. Seventeen out of 74 DBS (23%) with a “strong” positivity but none of 12 “weak” cases developed SNHL. CONCLUSIONS This study highlights the importance of testing DBS following a suitable algorithm in order of not missing cases with a low viral load. The confirmation of results will permit to have preliminary indications on prognosis, merely applying a method easy and cheap as the DBS-test.