RESUMO
<p><b>OBJECTIVE</b>To investigate the spontaneous YMDD mutation rate.</p><p><b>METHODS</b>Serum samples collected from 196 untreated chronic HBV patients were detected by primer-specific real-time PCR.</p><p><b>RESULTS</b>Among 196 patients, spontaneous YMDD variants were detected in 21 subjects (20 YVDD mutants and 1 YIDD mutant). YMDD variants account for more than 50%, 25% to 50%, 9% to 25% of total virus load in 1, 5 and 15 patients, respectively. Gender, age, HBeAg status, serum viral load, the state of disease and duration of infection were not associated with spontaneous YMDD mutation. Genotype B had higher spontaneous YMDD rate than genotype C (20.00% vs 7.38%, x(2) = 6.28, P < 0.05).</p><p><b>CONCLUSION</b>Spontaneous YMDD variants exist in chronic hepatitis B patients, Genotype B is associated with higher spontaneous YMDD rate.</p>