Misuse of the Lower Limit of Detection in HBV DNA Testing and Anti-HBe Positive Status Will Significantly Impact the Diagnosis of Occult HBV Infection

The diagnosis of occult hepatitis B virus (HBV) infection (OBI) is influenced by factors such as the lower limit of detection (LOD) of the HBV DNA test. However, in clinical practice and scientific research, the lower limit of quantification (LOQ) is often misused as the LOD. This study aims to investigate the impact of misuse of the LOD of the HBV DNA test on the detection rate of OBI, as well as the risk factors for OBI. Four hundred twelve patients who were HBsAg-negative and had undergone high-sensitivity HBV DNA testing were included in this study. HBV DNA was detected using the Cobas 6800 System with an LOD of 2.4 IU/mL and an LOQ of 10 IU/mL. The effect of using the LOQ as the LOD on the detection rate of OBI was compared, and univariate and multivariate logistic regression analyses were used to explore the risk factors for OBI. (1) Of the 412 patients, 63.3% (n = 261) were male, with a median age of 47 (range 34-55) years. A total of 473 HBV DNA test results were obtained, with 366 individuals undergoing only one HBV DNA test and the remaining 46 patients undergoing 2 to 5 HBV DNA tests (resulting in a total of 107 test results). (2) Considering only the first HBV DNA test result, the detection rate of OBI was 4.1% (17/412). However, when the LOQ (10 IU/mL) was used as the LOD, the detection rate of OBI was only 1.5% (6/412) (p < 0.001). (3) Univariate analysis showed that there were statistically significant differences in age, anti-HBe positivity rate and anti-HBc positivity rate between OBI and non-OBI individuals (p < 0.05). Multivariate regression analysis showed that anti-HBe positivity was an independent risk factor for OBI in this study (odds ratio [OR] = 3.807, 95% confidence interval [CI]: 1.065-13.617, p = 0.040), while anti-HBs positivity was a protective factor against OBI (OR = 0.271, 95% CI: 0.093-0.787, p = 0.016). (4) Among the 46 patients who underwent repeated testing, a total of seven individuals were found to be HBV DNA-positive in the first test, and six individuals tested positive for HBV DNA one or more times in subsequent tests. When OBI was confirmed by >= 1 out of 1-5 tests with detectable HBV DNA, the detection rate of OBI in this study could increase from 4.1% to 5.6%. The detection rate of OBI among HBsAg-negative adult patients attending hepatology departments in this region is 4.1%. Misusing the LOQ as LOD can significantly decrease the detection rate of OBI. The presence of anti-HBe positivity and undergoing multiple HBV DNA tests can lead to a significant increase in the detection rate of OBI.