Point -of -care testing (POCT) in molecular diagnostics: Performance evaluation of GeneXpert HCV RNA test in diagnosing and monitoring of HCV infection.

ABSTRACT

BACKGROUND: Molecular testing at the point-of-care may turn out to be game changer for HCV diagnosis and treatment monitoring, through increased sensitivity, reduced turnaround time, and ease of performance. One such assay GeneXpert® has recently been released. OBJECTIVES: Comparative analysis between performances of GeneXpert® and Abbott HCV-RNA was done. STUDY DESIGN: 174 HCV infected patients were recruited and, one time plasma samples from 154 patients and repeated samples from 20 patients, obtained at specific treatment time-points (0, 4, 12 and 24) weeks were serially re-tested on Xpert®. RESULTS: Genotype 3 was the commonest, seen in 80 (66%) of the cases, genotype 1 in 34 (28.3%), genotype 4 in 4 (3.3%) and genotypes 2 and 5 in 1 (0.8%) each. Median HCV RNA load was 4.69 log10 (range 0-6.98log10) IU/ml. Overall a very good correlation was seen between the two assays (R2=0.985), concordance of the results between the assays was seen in 138 samples (89.6%). High and low positive standards were tested ten times on Xpert® to evaluate the precision and the coefficient of variation was 0.01 for HPC and 0.07 for the LPC. Monitoring of patients on two different regimes of treatment, pegylated interferon plus ribavirin and sofosbuvir plus ribavirin was done by both the systems at baseline, 4, 12 and 24 weeks. Perfect correlation between the assays in the course of therapy at different treatment time- point in genotypes 3 and 1 was seen. CONCLUSION: The study demonstrates excellent performance of the Xpert® HCV assay in viral load assessment and in treatment course monitoring consistency.