Relationship between age and prevalence of hepatitis B infection in first-year university students in Hong Kong.

PURPOSE: To determine the effect of age on the prevalence of hepatitis B virus (HBV) infection during a routine screening programme of first-year students enrolled in Health Sciences Studies at the Chinese University of Hong Kong from 2001 to 2009. METHODS: In a retrospective cohort study, data on the hepatitis B surface antigen (HBsAg) status was retrieved from the University Health Service and analysed according to the age of the student at testing and year of birth. RESULTS: Of the 2,688 students enrolled in the study group, 79 (2.9 %) tested positive for HBsAg. The prevalence increased significantly from 0.9, 2.3, 4.3 to 5.5 % for those tested at age ≤ 18, 19, 20 and ≥ 21 years, respectively (p < 0.001). On logistic regression analysis, taking age ≤ 18 years and year of birth before 1983 (before the availability of HBV vaccination) as the reference group, HBV infection increased progressively with age, with an adjusted odds ratio of 3.36 [95 % confidence interval (CI) 1.01-11.23], 6.04 (95 % CI 1.74-20.98) and 11.61 (95 % CI 3.20-42.13) for age 19, 20 and ≥ 21 years, respectively. There was no significant change in the odds ratio after adjustment for the year of birth before and after introduction of the vaccination programme. CONCLUSION: Among the university students enrolled in our study, the overall prevalence of HBV infection before and after the introduction of HBV vaccination was lower than the 10 % found in the general population. There was, however, a significant progressive increase with age at testing from ≤ 18 to ≥ 21 years, suggesting a previously overlooked contribution of horizontal transmission to the high prevalence of HBV infection found in our adult population.

Correlation between maternal hepatitis B surface antigen carrier status with social, medical and family factors in an endemic area: have we overlooked something?

PURPOSE: Hepatitis B virus (HBV) infection is endemic in many countries, but the risk factors for HBV carriage in the obstetric population are unclear. METHODS: A survey on 1,580 women attending the antenatal clinic in an endemic region was conducted in order to examine the prevalence of and factors associated with maternal HBV carriage, including socio-demographic, medical, and previous obstetrical and family history, by means of a questionnaire. RESULTS: The prevalence of maternal HBV carriage was 9.1%, and 4.8% of women with a history of hepatitis B vaccination were found to be HBV carriers. Factors associated with maternal HBV carriage were residency status (adjusted odds ratio [aOR] 3.65 for immigrants; aOR 7.62 for non-residents), positive family history (aOR 3.72 for infected mother; aOR 5.36 for other family members), no previous vaccination (aOR 4.39) and having previous HBsAg testing (aOR 2.26). CONCLUSIONS: The findings suggest that there was probably an overlooked role of horizontal transmission within the family setting in addition to perinatal transmission in determining the likelihood of HBV infection in our obstetric population. Reconfirmation of hepatitis B status might be necessary among individuals with a history of vaccination to ensure the effectiveness of their immunoprotection.

A survey of prenatal first-trimester aneuploidy screening among Hong Kong specialist obstetricians.

OBJECTIVES: To determine the background, qualifications, and certification status of specialists currently performing first trimester screening in Hong Kong, the extent of their participation (and the laboratories they use) in quality assurance programmes, and their willingness to provide follow-up data for auditing purposes. DESIGN: Questionnaire survey. SETTING: Hong Kong. PARTICIPANTS: A survey was mailed to all registered Hong Kong specialist obstetricians. Results were reported using descriptive statistics. RESULTS: The response rate was 32% (106/331). Overall, 73% offered universal screening to all pregnant women. The majority (72%) most commonly performed first trimester screening for their patients. Sixty-six (62%) of the respondents performed nuchal translucency scanning; only 30 (45%) were accredited by a recognised body to perform such scans. Only 33% of the relevant laboratories used by specialists participated in external quality assurance programmes specific to Down's syndrome screening undertaken by a third party organisation. CONCLUSIONS: According to our data, first trimester screening has become one of the most common screening strategies for Down's syndrome in Hong Kong, but there is a need to assess the quality of such prenatal screening for aneuploidy to ensure its efficacy.

First-trimester fetal nasal bone length in an ethnic Chinese population.

OBJECTIVES: To determine reference ranges of fetal nasal bone length (NBL) in a Chinese population and to assess the value of NBL measurement in screening for chromosomal defects in the first trimester. METHODS: In this prospective study the fetal profile was examined and the fetal NBL and crown-rump length (CRL) were measured in Chinese women presenting with singleton pregnancies for first-trimester screening for aneuploidy between January 2004 and June 2007. Screening was performed on the basis of nuchal translucency (NT) measurement and maternal serum free beta-human chorionic gonadotropin and pregnancy-associated plasma protein-A levels. RESULTS: NBL was measured in 7543 fetuses, of which 7517 were euploid. The best fit equation for median NBL in euploid fetuses in relation to CRL was: NBL (mm) = 0.4593 + (0.0186 x CRL(mm)). The NBL for gestational age (GA, in days) was given by the equation NBL(mm) = 0.2392 + (0.0027 x GA). There was no correlation between log(10)(NBL multiples of the median (MoM)) and log(10)(NT MoM) in unaffected pregnancies (r = - 0.009; P = 0.43). Only two of the 11 cases with trisomy 21 had an NBL outside the 5(th) or 95(th) centiles of the reference range for euploid fetuses. CONCLUSION: Reference ranges for NBL in a Chinese population suitable for screening for aneuploidy between 11 and 13 + 6 weeks' gestation have been derived. The NBL in Chinese fetuses is similar to that of other ethnic groups. However, unlike the determination of presence vs. absence of the nasal bone, NBL measurement is unlikely to further improve screening for aneuploidy.

Fetal crown-rump length and estimation of gestational age in an ethnic Chinese population.

OBJECTIVES: To develop a sonographic dating formula based on fetal crown-rump length (CRL) in a Hong Kong Chinese population, quantify its systematic prediction error and compare its performance with established dating formulae. METHODS: This was a prospective observational study of women with a spontaneously conceived singleton pregnancy and a regular menstrual cycle in the preceding 12-month period. Ultrasound examinations were performed at gestational ages ranging from 6 to 15 + 6 weeks according to menstrual dates. The CRL of each fetus was measured three times, the mean of which was used to derive the best-fit fractional polynomial regression model for estimation of gestational age in relation to CRL. For each fetus, the menstrual age was compared to the gestational age calculated using three established dating formulae based on CRL measurement. The mean of the differences between estimated and menstrual age was calculated for each formula. RESULTS: Of the 394 subjects recruited one was excluded as the pregnancy resulted in intrauterine demise. The best-fit equation for the sonographic estimate of gestational age (GA, in days) from CRL (in mm) was GA = 26.643 + 7.822 x CRL(1/2)(R(2) = 0.96). The mean difference between menstrual age and the predicted gestational age was 0.22 days (95% CI, - 0.14 to 0.56), which was lower than that of the three established CRL dating formulae. CONCLUSION: We have derived a formula suitable for the dating of naturally conceived pregnancies between 6 and 15 weeks of gestation that has no systematic prediction error (the 95% CI of mean difference between predicted and menstrual age included zero), comparing favorably with established CRL dating formulae.

Trends in maternal obesity and associated risks of adverse pregnancy outcomes in a population of Chinese women.

OBJECTIVE: To assess the effect of increasing body mass index (BMI) on pregnancy outcome in a population of Chinese women. DESIGN: A retrospective study. SETTING: A university teaching hospital. POPULATION: Women delivering singleton babies between 1995 and 2005 who sought antenatal care before 20 weeks of gestation. METHODS: A total of 29,303 women were categorised into six BMI groups according to WHO's classification. Univariate, multivariate and logistic regression analysis were performed to compare obstetric and perinatal outcomes between BMI groups. MAIN OUTCOME MEASURES: Incidences of caesarean delivery, pre-eclampsia, gestational diabetes, preterm delivery, small for gestational age (SGA) and large for gestational age (LGA), perinatal death, and the respective odd ratios in reference to the normal group with BMI > or = 18.5 kg/m(2) and <23 kg/m(2). RESULTS: The median BMI increased with increasing maternal age, parity, gestation at the first visit, but decreased with year of delivery (P < 0.001). Concerning the obstetric outcomes, increasing BMI was associated with increasing incidence of caesarean section, pre-eclampsia, gestational diabetes, preterm delivery, LGA, as well as SGA according to customised growth standards (P < 0.001). The odds ratios for most of these adverse outcomes are higher than those reported in Caucasian population. Increasing BMI was not associated with the rate of stillbirth, neonatal death or shoulder dystocia. CONCLUSION: Increasing BMI is associated with increased risks of adverse obstetric outcomes. The impacts of high BMI on pre-eclampsia, gestational diabetes and preterm delivery in Chinese women might be stronger than that in Caucasian. Hence, it may be appropriate to use a lower BMI cutoff for defining overweight in Chinese.