Validity of a point-of-care viral load test for hepatitis B in a low-income setting

The recent launch of the first point-of-care Xpert® hepatitis B virus (HBV) viral load kit from Cepheid could help to scale up treatment for chronic hepatitis B (CHB) in resource-limited settings. This study aimed to assess the performance of the Xpert kit under field conditions in Ethiopia. One-hundred-and-thirty CHB patients with viral loads ranging from <1 log₁₀ to>7 log₁₀ IU/mL were randomly sampled. The viral load was assessed with both the Xpert and the gold standard Abbott RealTime HBV Viral Load assay in each patient. There was a high correlation between the viral loads assessed by Xpert and Abbott (r = 0.948, p < 0.001). The Bland-Altman plot showed a small bias between the two assays, with an on average 0.23 log₁₀ IU/mL higher viral load result of the Xpert kit; 4 samples differed by>1 log₁₀ IU/mL. Using the treatment threshold of 2000 IU/mL in both tests, Xpert had a sensitivity of 94 %, specificity of 71 %, positive predictive value of 70 %, and negative predictive value of 95 %. In conclusion, the Xpert kit demonstrated good validity for the measurement of HBV viral load in a real-life setting.