Evaluation of the COBAS® TaqMan® system in patients with low hepatitis B virus DNA undetectable with PCR assay kit.

OBJECTIVE We conducted a comparison of the diagnostic kit for quantification of hepatitis B virus DNA (PCR-fluorescence probing) and COBAS TaqMan automated nucleic acid extraction and real-time polymerase chain reaction (PCR) amplification systems. We tested their capacity to quantify and diagnose patients with chronic viral hepatitis B with low viral load < 1 x 103 IU/mL, in hope to provide further evidence for promoting the application of COBAS TaqMan as the diagnostic method for such patients. PATIENTS AND METHODS Diagnostic kit and COBAS TaqMan system were tested on 100 patients diagnosed with chronic viral hepatitis B in our hospital and with a viral load lower than the detection limit of real-time extraction-quantification kit. These patients included 47 cases with chronic viral HBV, 53 cases of HBV-associated cirrhosis (11 cases were HBV-associated liver cancer with cirrhosis). COBAS TaqMan real-time quantification PCR with a sensitivity of 20 IU/ml was performed to test the reproducibility for the diagnosis result. RESULTS The COBAS TaqMan real-time system quantified 76 cases out of 100 with a viral load higher than 20 IU/ml (detection rate, 76%). Among these patients, there were 33 cases of chronic viral HBV (without cirrhosis) (detection rate, 70.2%), 43 cases of cirrhosis (detection rate, 81.1%, including 28 cases of compensatory cirrhosis and 15 cases of decompensated cirrhosis), and 11 cases of liver cancer (detection rate, 81.2%). CONCLUSIONS The COBAS TaqMan system has higher sensitivity than traditional real-time PCR detection kit, especially for HBV-related cirrhosis and liver cancer with low viral load. The limitation of real-time PCR should be taken into account during treatment monitoring and the alternative of COBAS TaqMan system should be promoted in patients with high risk of liver cirrhosis and cancer to avoid delayed diagnosis and improve clinical outcome.