Diagnostic test accuracy of the cobas 6800 system for detection of hepatitis c virus viraemia levels from dried blood spots

Abstract

Introduction: Because hepatitis C virus (HCV) infection is curable in the majority of cases, the diagnosis of all infected patients has become a priority. In difficult-to-diagnose populations, simpler diagnostic methods are required such as the use of dried blood spots (DBS) as an alternative to blood drawn by venipuncture (VP). Before being able to include it as a HCV diagnostic detection method within the Spanish National Health System, the diagnostic accuracy of standard hospital equipment must be evaluated.

Methodology: DBS samples were evaluated in vitro and in a field test after being processed in the Cobas 6800 system, establishing a correlation with the result by VP. Performance with different viral loads and intra-assay variability was compared.

Results: In samples with a viral load of>3 log₁₀IU/ml, viraemia was detected in all cases when at least two blood spot elutions were used (94 detections out of 95 spot elutions). The performance with 2 spots was lower in samples with<3 log₁₀IU/ml (7/20). Correlation between VP and DBS viraemia was excellent (maximum with 2 spots, r²=0.906, P<.001) with a coefficient of variation of 0.05%. In routine clinical practice with specimens from screened subjects (n=61), excellent diagnostic accuracy was also observed.

Conclusion: Viral load detection using DBS of at least two spots is a reliable method for HCV diagnosis. The standardisation of the method is feasible and our results support the incorporation of this diagnostic tool in Spain's Public Health System.

Keywords: Análisis; Carga viral; Cirrhosis; Cirrosis; Infección; Infection; Screening; Viral load.