Clonal evolution of multidrug resistant hepatitis B virus during entecavir rescue therapy.

BACKGROUND & AIMS: Analysing the mutation pattern of multidrug resistance (MDR) is important in the treatment of chronic hepatitis B (CHB). In this study, the evolutionary pattern of MDR mutations was investigated in patients receiving entecavir (ETV) rescue therapy. METHODS: Eight CHB patients with lamivudine (LAM)- and adefovir (ADV)-resistant mutations showing suboptimal response to ETV and to subsequent ETV-plus-ADV therapy were enrolled. The clonal evolution of the mutation pattern was investigated through direct sequencing, multiplex restriction fragment mass polymorphism (RFMP), and clonal analysis and the utility of these methods was compared. RESULTS: Among 160 clones at baseline, wild-type hepatitis B virus (HBV) was present in 62 (38.8%), LAM-resistant mutations in 92 (57.6%) and ADV-resistant mutations in 55 (34.4%). LAM-resistant mutations increased to 70.6% at the end of ETV therapy and increased to 74.4% at the 12th month of ETV-plus-ADV therapy. During the same time periods, ETV-resistant mutations were present in 46.3% and 38.8%, and ADV-resistant mutations were present in 3.1% and 9.4% respectively. When 256 nucleotides from 32 samples were examined for mutations, clonal analysis detected 93 mutations (36.3%), direct sequencing detected 36 mutations (14.1%) and RFMP detected 73 mutations (28.5%). The sensitivity (73.1%, 95% CI; 64.1-82.1%) and specificity (96.9%, 95% CI; 94.4-99.4%) of RFMP were high, showing a concordance rate of 88.3% with the results from clonal analysis. All mutations exceeding 40% of the total clones detected by clonal analysis were also detected by RFMP. CONCLUSIONS: The clonal evolution of the mutation pattern in MDR HBV showed the selection of LAM-resistant (±ETV-resistant) HBV during ETV rescue therapy, which may be the primary reason for patients' suboptimal response. Multiplex RFMP is a useful method for detecting MDR mutations in clinical practice.

Fetal growth and neonatal mortality in Korea.

The fetal growth curve and neonatal mortality rate, based on gestational age and birthweight, are important for identifying groups of high-risk neonates and developing appropriate medical services and health-care programmes. The purpose of this study was to develop a national fetal growth curve for neonates in Korea, and examine the Korean national references for fetal growth and death according to their characteristics. Data of Korean vital statistics linked National Infant Mortality Survey conducted on births in 1999 were used in this study. The total livebirths were 621,764 in 1999, which were grouped into singletons (n = 609,643) and twins (n = 9805) for analysis. Birthweight/gestational age-specific fetal growth curves and neonatal mortality rates were based on 250 g of birthweight and weekly gestational age intervals for each characteristic of the birth. The features of high-risk neonates such as small-for-gestational-age and the limit of viability in Korea were different from those of Western countries. Difference in fetal growth and death was also detected in other characteristics of the fetus (gender and plurality of birth) besides race. The fetal growth curve of males was higher than that of females, and was higher in singleton than in twins. The neonatal mortality rate was higher in males (singleton, 2.6; twin, 23.5) than females (singleton, 2.1; twin, 15.9), and higher in twins (19.8/1000) than in singletons (2.4/1000). However, in neonates with gestational age >29 weeks and birthweight >1000 g, the neonatal mortality rate was lower in twins than in singletons. The limit of viability was gestational age 27 weeks and birthweight 1000 g, which was similar in singletons and twins regardless of gender. To improve the health of neonates in a country, it is imperative to investigate the characteristics of fetal growth and death under the particular circumstances of the country. When risk is defined for neonates account must be taken of differences in race, gender and plurality of birth, as the neonatal mortality rate varies depending on those factors.