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Biomedical subjects

K Y Leung

Publications and source records attributed to K Y Leung.

At least 19 recordsLinked to original sources
PubMed2006

Continued reduction in the incidence of birth trauma and birth asphyxia related to instrumental deliveries after the study period: was this the Hawthorne effect?

BACKGROUND: The incidence of birth trauma and birth asphyxia related to instrumental deliveries in our obstetric unit was high (2.8%) in 1998-1999. A study was performed in 2000 to identify the risk factors. Unexpectedly, the incidence (0.6%) was reduced significantly during the study period. We attributed this phenomenon to the famous Hawthorne effect (tendency to improve performance because of awareness of being studied). OBJECTIVES: The objectives were to study whether there is a continued reduction in the incidence of birth trauma and birth asphyxia related to instrumental deliveries in the post-study period (2001-2003) and to investigate the presence of underlying confounding factors apart from the Hawthorne effect. METHOD: To compare the hospital obstetric statistics among the pre-study period (1998-1999), the study period (2000) and the post-study period (2001-2003), in particular the incidence of birth trauma and birth asphyxia related to instrumental deliveries, the instrumental delivery rate, the overall Caesarean section rate, the Caesarean section rate for no progress of labour, the incidence of failed instrumental delivery, the incidence of attempted instrumental delivery in the operating theatre, and incidence of direct second-stage Caesarean sections. RESULTS: The incidence of birth trauma and birth asphyxia related to instrumental deliveries (0.6%) during the study period (2000) was significantly lower than that (2.8%) during the pre-study period (1998-1999; RR 0.27, 95% CI 0.11-0.70). This phenomenon continued into the post-study period (2001-2003) when the incidence of 1.0% was similarly lower than that in the pre-study period (RR 0.35, 95% CI 0.20-0.64). The instrumental delivery rate decreased further in the post-study period (13.5%) compared with those in the study (16.6%) and pre-study (19.5%) periods (RR 0.81, 95% CI 0.75-0.89 and RR 0.69, 95% CI 0.65-0.74, respectively). There was a marked increase in the direct second-stage Caesarean section rate in the post-study period (7.1%) compared to those in the study (0.4%) and pre-study (0.7%) periods (RR 15.9, 95% CI 5.05-49.73 and RR 9.77, 95% CI 5.28-18.08, respectively). CONCLUSION: A change in obstetric practice was identified that may explain the continued reduction in the incidence of birth trauma and birth asphyxia related to instrumental deliveries in the post-study period.

Asphyxia Neonatorum↗
PubMed2006

Full karyotyping, rapid aneuploidy diagnosis or both when invasive prenatal testing is performed for diagnosis of thalassaemia?

A retrospective study was performed to compare the detection rate of chromosomal abnormalities by different approaches of full karyotyping, rapid aneuploidy diagnosis (RAD) or both when invasive prenatal testing is performed for diagnosis of thalassaemia. The karyotype results of 1120 prenatal samples obtained from thalassaemia couples from January 1985 to December 2002 in a referral centre for prenatal diagnosis were studied. The detection rate of chromosomal abnormalities by four different approaches were compared: (i) karyotyping for all samples; (ii) RAD (21,18,13,X,Y) for all samples; (iii) RAD for all samples + karyotyping for cases with ultrasound abnormalities; and (iv) RAD (21,18,13) for all + RAD (X,Y) for cases with ultrasound abnormalities consistent with Turner syndrome + karyotyping for cases with ultrasound abnormalities. Normal karyotypes were found in 1103 samples (98.5%). There were 17 cases (1.5%) of chromosomal abnormalities: four cases (0.36%) were clinically significant, eight cases (0.7%) were of borderline clinical significance and five cases (0.44%) were not confirmed by subsequent prenatal or postnatal tests. The incidences of autosomal (7/1120 = 0.63%) and sex chromosomal (5/1120 = 0.45%) abnormalities were not higher than those (0.41 and 0.22%, respectively) from newborn surveys (Hook and Hamerton, 1977) (P = 0.398 and 0.216, respectively). Approach 1 would detect all 17 chromosomal abnormalities. Approach 2 would detect three of four clinically significant chromosomal abnormalities but not detect six of eight chromosomal abnormalities of borderline clinical significance and three of five chromosomal abnormalities not confirmed by subsequent prenatal or postnatal tests. Approach 3, in addition, would be able to detect all four clinically significant chromosomal abnormalities. Approach 4 would detect all four clinically significant chromosomal abnormalities but would not detect seven of eight chromosomal abnormalities of borderline clinical significance and four of five chromosomal abnormalities not confirmed by subsequent prenatal or postnatal tests. RAD (21,18,13) for all + RAD (X,Y) for cases with ultrasound abnormalities consistent with Turner syndrome + karyotyping for cases with ultrasound abnormalities seemed to be the best approach for the detection of chromosomal abnormalities when invasive prenatal testing is performed for diagnosis of thalassaemia.

Adolescent↗
PubMed2006

A new strategy for prenatal diagnosis of homozygous alpha(0)-thalassemia.

OBJECTIVES: We have shown previously that ultrasound examination performed by one experienced operator can be useful to exclude homozygous alpha(0)-thalassemia in a tertiary referral center. This study aimed to determine whether the technique was still applicable when performed by several operators and in different centers. METHODS: At the Maternal and Neonatal Hospital of Guangzhou (MNH) and Tsan Yuk Hospital of Hong Kong (TYH), women at risk of homozygous alpha(0)-thalassemia were given the option of a non-invasive approach (using serial ultrasound examinations at 12-15, 16-20 and 25-30 weeks' gestation) to exclude an affected pregnancy. The fetal cardiothoracic ratio (CTR) was measured at each of these examinations and the placental thickness was measured at 12-15 weeks' gestation. The operators of MNH received training on the ultrasound examination techniques at TYH and the quality of the subsequent ultrasound examinations was checked regularly. The final diagnosis of homozygous alpha(0)-thalassemia was confirmed using an invasive test. RESULTS: Of 832 at-risk pregnancies studied in the two hospitals, 168 (20.2%) were affected. The overall sensitivity and specificity of the non-invasive approach was 100% and 95.6%, respectively. At MNH, the need for an invasive test was reduced by 80.8%, and all the affected pregnancies were diagnosed before 24 weeks' gestation. The results achieved at MNH were comparable with those at TYH. The at-risk pregnancies including the affected ones presented at a more advanced gestational age at MNH. At each hospital, one affected pregnancy was missed at the 12-week scan but this was subsequently detected at the 15-18-week scan. CONCLUSIONS: This non-invasive approach to exclude homozygous alpha(0)-thalassemia can be applicable when it is performed by several operators and in different centers.

Cardiomegaly↗
PubMed2006

Placental volume measured by three-dimensional ultrasound in the prediction of fetal alpha(0)-thalassemia: a preliminary report.

OBJECTIVE: To evaluate the use of placental volume measured by three-dimensional (3D) ultrasound in predicting fetal homozygous alpha(0)-thalassemia (Hb-Bart's disease). METHODS: From June 2002 to May 2004 singleton pregnancies at risk of alpha(0)-thalassemia and normal controls were studied prospectively at 9-12 weeks of gestation. Affected fetuses were suspected to have alpha(0)-thalassemia by two-dimensional (2D) ultrasound and confirmed by DNA analysis. Placental volume was measured on 3D ultrasound by a multiplanar technique. Intra- and interobserver agreement of measurements was assessed. The placental volume/crown-rump length quotient of the affected fetuses was compared with that of normal fetuses. RESULTS: The final study group comprised 105 pregnancies; 43 were at risk of alpha(0)-thalassemia and 62 were normal controls. Eleven (10.5%) fetuses were affected by alpha(0)-thalassemia, all from the at-risk group, and the others were normal. Intra- and interobserver agreement of volume measurement by 3D ultrasound was relatively poor; this was reflected in the wide limits of agreement, which ranged from -10.82 to 40.86 mL. The mean +/- SD placental volume/crown-rump length quotient in affected pregnancies was larger than that in unaffected pregnancies (1.37 +/- 0.65 vs. 1.13 +/- 0.39), but this difference was not significant (P > 0.05). CONCLUSIONS: Assessment of placental volume by 3D ultrasound does not seem to be superior to 2D ultrasound in the first-trimester prediction of alpha(0)-thalassemia.

Adult↗
PubMed2006

The effects on maternal anxiety of two-dimensional versus two- plus three-/four-dimensional ultrasound in pregnancies at risk of fetal abnormalities: A randomized study.

OBJECTIVE: To test the hypothesis that the use of two-dimensional (2D) ultrasonography with three-dimensional/four-dimensional (3D/4D) ultrasonography can reduce anxiety to a greater extent in women at risk of having a fetus with congenital abnormalities than the use of 2D ultrasonography alone. METHODS: A total of 124 women attending the prenatal diagnostic clinic of a teaching hospital were randomized into the intervention group (2D ultrasonography followed by 3D/4D ultrasonography) or control group (2D ultrasonography alone). The primary outcome was maternal anxiety levels, which were assessed by the Spielberger state-trait anxiety inventory. We measured the anxiety levels in all women at the first visit, at around 18 weeks' gestation (immediately after ultrasound examinations) and at 28 weeks' gestation. RESULTS: A short-term reduction of the state-anxiety score (by around 2 points) from the first visit to after ultrasound examinations was observed in both the intervention group and the control group. Unexpectedly, a small increase in the state-anxiety score from the first visit to 28 weeks' gestation was observed in the intervention group but not in the control group, though there was no significant difference in the changes between the two groups. Repeated measures ANOVA (analysis of variance) also showed that there was no significant interaction effect between groups and time of assessment on the state-anxiety scores (F = 1.072 and P = 0.344). About 80% of women reported a better understanding that their baby was normal after viewing 3D rather than 2D images. CONCLUSION: This randomized study indicates that the addition of 3D/4D ultrasound does not cause a significant reduction in maternal anxiety in pregnancies at risk of fetal abnormalities compared with conventional 2D ultrasound alone.

Adult↗
PubMed2005

Use of hormone replacement therapy in the Hong Kong public health sector after the Women's Health Initiative trial.

OBJECTIVES: To determine the impact of Women Health Initiative (WHI) trial on the use of hormone replacement therapy (HRT) in the Hong Kong public health sector. METHODS: The central prescription database of the Hospital Authority was used to describe the half-yearly trend in the use of HRT between July 2000 and December 2003. The data of hysterectomy was retrieved from another clinical database. RESULTS: Before the publication of the WHI trial in July 2002, conjugated equine estrogens (CEE) and its related products dominated HRT prescribing. Relative to the first half of 2002, there was an immediate and substantial decline by 43.5% in the prescriptions of combined CEE/progestogen products and a modest decline by 22.4% in the prescriptions of CEE-alone therapy in the second half of 2002. In the first half of 2003, a decline in the prescriptions of all HRT preparations except raloxifene was observed. However, in the second half of 2003, there were no more declines in overall HRT users. Relative to the first half of 2002, the decline in the overall HRT users in the first half of 2003 was more than 46% in women aged 50-69. The decline was greater in women with a history of hysterectomy (60.3%) than women without (38.6%), but was similar between gynaecology specialty (41.7%) and non-gynaecology specialty (43.9%). CONCLUSIONS: Similar to the U.S., an immediate and substantial decline in the use of CEE and its related products was observed in Hong Kong after the publication of the WHI trial.

Age Factors↗
PubMed2005

Simple non-invasive prenatal detection of Hb Bart's disease by analysis of fetal erythrocytes in maternal blood.

OBJECTIVE: To investigate a simple non-invasive technique for early detection of Hemoglobin (Hb) Bart's disease. METHOD: Maternal blood smears from 8 known Hb Bart's pregnancies and 40 at-risk pregnancies were investigated. Maternal peripheral blood smears were stained with fluorescence-labeled monoclonal antibodies against alpha- and embryonic zeta-globin chains. RESULTS: Fetal nonnucleated red blood cells, stained with anti-zeta but not with anti-alpha globin antibodies were found in 15 out of 16 affected pregnancies but were not detected in 23 out of 24 unaffected pregnancies. CONCLUSION: Results showed that non-invasive immunofluorescence staining of maternal blood is a feasible approach for screening Hb Bart's disease before ultrasound manifestation in affected pregnancies.

Antibodies, Monoclonal↗
PubMed2005

Three-dimensional extended imaging: a new display modality for three-dimensional ultrasound examination.

OBJECTIVE: To describe Three-Dimensional eXtended Imaging (3DXI) as a new display modality for three-dimensional (3D) ultrasound examination of the fetus. METHODS: The spine, palate, heart and brain were evaluated using 3D ultrasound examination at a mean gestational age of 22 weeks in 35, 31, 32 and 31 fetuses, respectively. The volume data captured were analyzed using the conventional orthogonal display mode (ODM), as well as the 3DXI, which includes the Multi-Slice View (MSV) mode and the Oblique View (OBV) mode. The MSV mode allows simultaneous display of multiple sequential parallel planes while the OBV mode allows examination of a non-standard straight or curved plane. RESULTS: The MSV mode allowed a simultaneous display of multiple sequential parallel planes of the fetal structures, but we found some uncertainty if an isolated image in one of the multi-slice images represented the exact level of a fetal structure. The MSV mode was advantageous in one of the six cases of facial cleft by allowing the simultaneous display of bilateral clefts that were located in two different axial planes. The multi-slice images were helpful in making the diagnosis in one case of holoprosencephaly. The OBV mode allowed examination of the coronal plane across the curvature of the spine, and the 'in-plane' view of the interventricular septum in a non-gated study. CONCLUSION: The 3DXI can display the volume data in a different manner from that which usually results from the use of more conventional ODM, and provide additional information over conventional two-dimensional sonography.

Cardiovascular Abnormalities↗
PubMed2005

Role of type III secretion in Edwardsiella tarda virulence.

Edwardsiella tarda is a Gram-negative enteric bacterium affecting both animals and humans. Recently, a type III secretion system (TTSS) was found in Ed. tarda. Such systems are generally used by bacterial pathogens to deliver virulence factors into host cells to subvert normal cell functions. Genome-walking was performed from the eseB and esrB genes (homologues of Salmonella sseB and ssrB, respectively) identified in previous studies, to determine the sequences of the TTSS. Thirty-five ORFs were identified which encode the TTSS apparatus, chaperones, effectors and regulators. Mutants affected in genes representing each category were generated and found to have decreased survival and growth in fish phagocytes. LD(50) values of the mutants were increased by at least 10-fold in comparison to those of the wild-type strain. The adherence and invasion rates of the esrA and esrB mutants were enhanced while those of the other mutants remained similar to the wild-type. The eseC and eseD mutants showed slight autoaggregation in Dulbecco's Modified Eagle Medium, whereas the rest of the mutants failed to autoaggregate. Regulation of the TTSS was found to involve the two-component regulatory system esrA-esrB. This study showed that the TTSS is important for Ed. tarda pathogenesis. An understanding of this system will provide greater insight into the virulence mechanisms of this bacterial pathogen.

Bacterial Proteins↗
PubMed2005

Identification and characterization of putative virulence genes and gene clusters in Aeromonas hydrophila PPD134/91.

Aeromonas hydrophila is a gram-negative opportunistic pathogen of animals and humans. The pathogenesis of A. hydrophila is multifactorial. Genomic subtraction and markers of genomic islands (GIs) were used to identify putative virulence genes in A. hydrophila PPD134/91. Two rounds of genomic subtraction led to the identification of 22 unique DNA fragments encoding 19 putative virulence factors and seven new open reading frames, which are commonly present in the eight virulence strains examined. In addition, four GIs were found, including O-antigen, capsule, phage-associated, and type III secretion system (TTSS) gene clusters. These putative virulence genes and gene clusters were positioned on a physical map of A. hydrophila PPD134/91 to determine their genetic organization in this bacterium. Further in vivo study of insertion and deletion mutants showed that the TTSS may be one of the important virulence factors in A. hydrophila pathogenesis. Furthermore, deletions of multiple virulence factors such as S-layer, serine protease, and metalloprotease also increased the 50% lethal dose to the same level as the TTSS mutation (about 1 log) in a blue gourami infection model. This observation sheds light on the multifactorial and concerted nature of pathogenicity in A. hydrophila. The large number of putative virulence genes identified in this study will form the basis for further investigation of this emerging pathogen and help to develop effective vaccines, diagnostics, and novel therapeutics.

Aeromonas hydrophila↗
PubMed2005

Regulation of a type III and a putative secretion system in Edwardsiella tarda by EsrC is under the control of a two-component system, EsrA-EsrB.

Edwardsiella tarda is a gram-negative enteric pathogen that causes hemorrhagic septicemia in fish and gastro- and extraintestinal infections in humans. A type III secretion system (TTSS) and a putative secretion system (EVP) have been found to play important roles in E. tarda pathogenesis. Our previous studies suggested that the TTSS and EVP gene clusters were regulated by a two-component system of EsrA-EsrB. In the present study, we characterized another regulator, EsrC, which showed significant sequence similarity to the AraC family of transcriptional regulators. Mutants with in-frame deletions of esrC increased the 50% lethal doses in blue gourami fish, reduced extracellular protein production, and failed to aggregate. Complementation of esrC restored these three phenotypes. Two-dimensional gel electrophoresis showed that EsrC regulated the expression of secreted proteins encoded by the TTSS (such as EseB and EseD) and EVP (EvpC) gene clusters. The expression of esrC required a functional two-component system of EsrA-EsrB. EsrC in turn regulated the expression of selected genes encoded in TTSS (such as the transcriptional unit of orf29and orf30, but not esaC) and genes encoded in the EVP gene cluster. The present study sheds light on the regulation of these two key virulence-associated secretion systems and provides greater insight into the pathogenic mechanisms of this bacterium.

Amino Acid Sequence↗
PubMed2004

Continuation rate of hormone replacement therapy in Hong Kong public health sector.

OBJECTIVES: To assess the 1-year continuation rate of HRT prescribed in Hong Kong public health sector and to identify factors affecting this continuation rate. METHODS: All women who received at least one dispensed prescription of estrogens between January 1998 and December 2000 from 36 specialist outpatient clinics of the Hospital Authority were selected, and observed for at least 2 years and at most 3 years. The duration of use and variables including age, types of hormones, routes of delivery, dose of estrogen, and prescribing specialty were retrieved from the central prescription database of the Hospital Authority. RESULTS: Of 12,711 incident users of HRT, more than half were aged 50-59. Most (78.5%) of the users took conjugated equine estrogens (CEE) 0.625 mg or related products. Only a small proportion (3.0%) of women used CEE 0.3 mg. Initial estrogen prescriptions were written by gynaecologists in 86.7%. The overall 1-year continuation rate was 68.3%. The highest and lowest continuation rates were observed in women aged 40-49 and the two extreme age groups (35-39 and 70-79), respectively. Better continuation rate was observed in women taking estrogen-only therapy such as CEE or estradiol (overall 76.3%) than in women using continuous combined therapy (58.6%), sequential combined therapy (64.8%), or transdermal estrogen (60.6%). In the age group 60-69, the use of CEE 0.3 mg was associated with better continuation rate than CEE 0.625 mg. CONCLUSIONS: Better continuation rate at 1 year was associated with age younger than 60, oral route of HRT and hysterectomy.

Adult↗
PubMed2004

Cost-effectiveness of prenatal screening for thalassaemia in Hong Kong.

OBJECTIVES: To determine the cost effectiveness of a universal prenatal screening program for alpha- and beta-thalassaemia. METHODS: We retrospectively reviewed our program from 1998 to 2002, and calculated the direct and indirect costs of various components. RESULTS: 18,936 women were screened at our prenatal clinic and 153 couples were subsequently referred to our Prenatal Diagnostic Centre for counselling and further investigations. In addition, there were 238 tertiary referrals and 157 self-referrals. After investigations, 84 fetuses were at risk of beta-thalassaemia major/beta-E thalassaemia, 19 of them were affected and 18 were aborted. The total expenditure on our program (HK 10.0 million dollars) would be less than the postnatal service costs (HK 40.4 million dollars) for 18beta-thalassaemia major fetuses if they were born. Of 361 women at risk of carrying a homozygous alpha0-thalassaemia fetus, 311 (86.2%) opted for the indirect approach (using serial ultrasound examinations to exclude Hb Bart's disease), and 76 (24.5%) subsequently underwent an invasive test for a definitive diagnosis. The sensitivity and false positive rate of this indirect approach was 100.0% and 2.9% respectively. CONCLUSION: It is cost effective to run a universal prenatal screening program in an area where both beta-thalassaemia and alpha-thalassaemia are prevalent. The indirect approach can effectively avoid an invasive test in unaffected pregnancies.

Cost-Benefit Analysis↗
PubMed2004

Randomised trial comparing an interactive multimedia decision aid with a leaflet and a video to give information about prenatal screening for Down syndrome.

OBJECTIVES: (1)To compare an interactive multimedia decision aid (IMDA) with a leaflet and a video to give information about prenatal screening for Down syndrome and (2) to determine the women's acceptance of IMDA. METHODS: Two hundred and one women were recruited from the prenatal clinic of a university teaching hospital and randomised into the intervention group (IMDA, video, and information leaflet) or the control group (video and information leaflet). RESULTS: There were no significant differences in the initial decision for and the final uptake of the prenatal screening test between the control and intervention groups. The proportion of women who were undecided was less than 10% in both groups. Of the women in the intervention group, 86.6% and 78.9% agreed that IMDA was user-friendly and acceptable, respectively. Significantly more women aged < 35 (88.1%) accepted IMDA than women aged > or = 35 (68.3%) (P = 0.030), but the logistic regression analysis did not confirm this finding after adjusting for other factors (computer knowledge and usage of computer). CONCLUSION: The use of IMDA did not affect the women's overall uptake rate of the prenatal screening test for Down syndrome. More women less than 35 years accepted IMDA probably because they used computer more frequently and had more computer knowledge.

Adult↗