OBJECTIVETo compare the sensitivities of MALDI-TOF MS and direct PCR sequencing on gene mutations detection of hepatitis B virus.

METHODS100 serum samples from chronic hepatitis B patients were collected, which consisted of 90 serum samples (study group) from 90 chronic hepatitis B patients received nucleoside analogues (NA) therapy for more than 1 year and HBV DNA titer still higher than 500 copies/ml and 10 serum samples (blank group) from 10 chronic hepatitis B patients never treated with antiviral therapy and HBV-DNA titer higher than 1 x 10(5) copies/ml. 9 known mutations associated with HBV P gene in these samples were detected by MALDI-TOF MS and direct PCR sequencing at the same time, TYPE4.0 software and Sequence Navigator software were used to analyze the results separately.

RESULTS(1) In study group, mutations were detected in 53 samples and the total mutation sites were 86 by MALDI-TOF MS with a positive detection rate of 58.89%, whereas only 19 samples were found with mutations and totally 28 mutation sites were detected by direct PCR sequencing, the positive detection rate was 21.11%. The positive detection rate by MALDI-TOF MS was higher than that by direct PCR sequencing and the difference was statistically significant (P < 0.05). In blank group, no mutations were detected by any method. (2) In study group, when the HBV DNA titers were at 500-1000 copies/ml, 10(3)-10(4) copies/ml and 10(4)-10(5) copies/ml, the positive mutation detection rates by MALDI-TOF MS were 50%, 52.08% and 77.27% respectively, higher than that by direct PCR sequencing, which were only 0%, 8.33% and 45.45%. The difference was still statistically significant (P < 0.05).

CONCLUSIONSMALDI-TOF MS had higher detection sensitivity for known mutation sites as compared to direct PCR sequencing method.