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Biomedical subjects

D Machin

Publications and source records attributed to D Machin.

At least 19 recordsLinked to original sources
PubMed2003

Risk factors for nuclear, cortical and posterior subcapsular cataracts in the Chinese population of Singapore: the Tanjong Pagar Survey.

AIM: To describe risk factors for nuclear, cortical, and posterior subcapsular (PSC) cataracts in Chinese Singaporeans. METHODS: A population based cross sectional study was carried out on ethnic Chinese men and women aged 40-81 years. A stratified, clustered, disproportionate (more weights to older people), random sampling procedure was used to initially select 2000 Chinese names of those aged 40-79 years from the 1996 electoral register in the Tanjong Pagar district in Singapore. Eligible subjects (n = 1717) were invited for a standardised ocular examination and interview at a centralised clinic, following which an abbreviated examination was conducted for non-respondents in their homes. Cataract was graded clinically using to the Lens Opacity Classification System (LOCS) III system. The main outcome measures were adjusted odds ratio for risk factors for specific cataract types (nuclear, cortical and PSC), any cataract and cataract surgery, examined in multiple logistic regression models. RESULTS: Out of the 1232 (71.8%) examined, 1206 (70.2%) provided lens data for this analysis. Increasing age was associated with all cataract types, any cataract, and cataract surgery. There was no significant sex difference in presence of any cataract, specific cataract types or cataract surgery. After controlling for age, sex, and other factors, diabetes was associated with cortical cataract (3.1; 95% CI: 1.6 to 6.1), PSC cataract (2.2; 95% CI 1.2 to 4.1), any cataract (2.0; 95% CI: 0.9 to 4.5), and cataract surgery (2.3; 95% CI: 1.3 to 4.1). Lower body mass index was associated with cortical cataract (1.8; 95% CI: 1.1 to 2.9; lowest versus highest quintile) and any cataract (2.3; 95% CI: 1.3 to 4.0). Current cigarette smoking was associated with nuclear cataract (1.7, 95% CI: 1.0 to 2.9; more than 10 cigarettes per day versus none). A non-professional occupation was associated with nuclear cataract (2.9; 95% CI: 1.5 to 5.8; for production or machine operators and 2.6; 95% CI: 1.2 to 5.5; for labourers or agricultural workers, both versus professionals). Lower education was associated with nuclear cataract (2.3; 95% CI: 1.0 to 5.2, none versus tertiary), while lower household income was associated with PSC cataract (4.7, 95% CI: 1.1 to 20.0; income S$4000). CONCLUSIONS: Age related cataracts are associated with a variety of risk factors among Chinese people in Singapore, similar to those reported in European, Indian, and African derived populations. These data support common aetiological mechanisms for age related cataracts, irrespective of ethnic origin.

Adult↗
PubMed2003

Pilot study using technetium-99m pertechnetate sequential radionuclide-sialography to assess salivary gland function in nasopharyngeal cancer patients on radiation therapy.

INTRODUCTION: Nasopharyngeal carcinoma (NPC) is mainly treated by radiation therapy. A common complication of radiotherapy is xerostomia. Direct measurements of the amount of saliva produced using suction cups and volumetric assessments are cumbersome and time-consuming. Sequential radionuclide sialography is a reproducible and convenient method of measuring salivary function. MATERIALS AND METHODS: Patients with newly diagnosed NPC underwent a pilot study using technetium-99m pertechnetate sequential radionuclide sialography to assess their salivary function before and at 3 months post radiation therapy. From the sialography, time activity curves were obtained for analysis of salivary function. The shape of the time activity curve with citric acid stimulation was classified into 4 types according to the degree of radiation-induced dysfunction. RESULTS: All 14 patients had worse (P < 0.005) time activity curves for both parotids and submandibular glands after radiation therapy. All patients with abnormal curves before radiation therapy presented type IV (non-functioning) curve after radiation therapy. A ratio of pre- and post-stimulation counts allowed for quantification of the degree of stimulatory response. We found a significant decrease in Rc before and after radiation therapy for all salivary glands (P < 0.001). The salivary gland to background ratio, which is a reflection of the degree of salivary gland functional uptake, also had a significant reduction after radiation. CONCLUSION: It is feasible to use technetium-99m pertechnetate in the measurement of salivary gland function in nasopharyngeal cancer patients treated with radiation therapy.

Adult↗
PubMed2002

Association between psychological symptoms in adults and growth in early life: longitudinal follow up study.

OBJECTIVES: To test the hypothesis that birth weight for gestational age and weight gain in early childhood have a long term association with psychological distress in adults. DESIGN: Longitudinal study of 1958 birth cohort followed to age 42 years. SETTING: Population based birth cohort study. PARTICIPANTS: 9731 cohort members with valid perinatal, postnatal, and adult data. MAIN OUTCOME MEASURES: Malaise inventory scores measured at ages 23, 33, and 42 years. Generalised estimating equations approach used to analyse repeated measures. RESULTS: Psychological distress score was inversely related to birthweight z score and weight gain from birth to the age of 7 years. A unit increase in birthweight z score or childhood weight gain was associated with a mean reduction in psychological distress score of 0.10 (95% confidence interval 0.05 to 0.15) and 0.06 (0.02 to 0.10), respectively. Birth weight and weight gain were also inversely related to the odds of having a high level of psychological distress, with odds ratios being 0.90 (0.85 to 0.95) and 0.93 (0.89 to 0.98), respectively. CONCLUSIONS: Psychological health in adults is related to fetal growth and growth in early childhood.

Adult↗
PubMed2002

A review of the rheology of the lamellar phase in surfactant systems.

The rheology of the liquid crystal lamellar phase has been studied in a wide range of systems including non-ionic, anionic and cationic surfactants and block co-polymers. This review summarises the main advances in this area over the past twenty years and includes examples of the rheo-optical techniques, which help to elucidate the changes in microstructural conformation taking place in the lamellar phase during shear. Particular emphasis is given to the microstructural change of the lamellar phase from sheet-like bilayers to dispersed multilamellar vesicles (droplets). Examples of this transition are provided for both surfactant and block co-polymer systems. The review highlights similarities in the rheological signatures of the transition for different systems and also summarises the variation in behaviour of the lamellar phase at different surfactant concentrations and on the addition of salt.

Journal Article↗
PubMed2002

A Bayesian re-assessment of two Phase II trials of gemcitabine in metastatic nasopharyngeal cancer.

The Simon two-stage minimax design is a popular statistical design used in Phase II clinical trials. The analysis of the data arising from the design typically involves the use of frequentist statistics. This paper presents an alternative, Bayesian, approach to the design and analysis of Phase II clinical trials. In particular, we consider how a Bayesian approach could have affected the design, analysis and interpretation of two parallel Phase II trials of the National Cancer Centre Singapore, on the activity of gemcitabine in chemotherapy-naïve and in previously treated patients with metastatic nasopharyngeal carcinoma. We begin by explaining the Bayesian methodology and contrasting it with the frequentist approach. We then carry out a Bayesian analysis of the trial results. The conclusions drawn using the Bayesian approach were in general agreement with those obtained from the frequentist analysis. However they had the advantage of allowing for different and potentially more useful interpretations to be made regarding the trial results, as well as for the incorporation of external sources of information. In particular, using a Bayesian trial design, we were able to take into account the results of the parallel trial results when deciding whether to continue each trial beyond the interim stage.

Antimetabolites, Antineoplastic↗
PubMed2002

Use of the intra-aortic balloon pump for dilatation of benign tracheobronchial strictures.

Tracheobronchial benign stenoses may cause life-threatening emergencies. Here, we will describe a novel technique for the management of tracheal and bronchial stenoses using an intra-aortic balloon pump. The intra-aortic balloon pump was used for dilatation of a postoperative tracheal stricture in a 43-year-old man and a bronchial stricture in a 29-year-old woman with Wegener's granulematosis. There were no intraoperative or postoperative complications in either patient, and the stenosis was relieved successfully in each patient. The intra-aortic balloon pump can be used safely and effectively for the management of difficult tracheobronchial strictures.

Adult↗
PubMed2002

Gemcitabine in metastatic nasopharyngeal carcinoma of the undifferentiated type.

BACKGROUND: We conducted two parallel phase II trials in chemonaïve and previously treated patients with metastatic nasopharyngeal carcinoma (NPC) to evaluate the tumour response, progression-free and overall survival, and toxicity of gemcitabine. PATIENTS AND METHODS: Gemcitabine 1250 mg/m2 was given on days 1 and 8 of a 21-day cycle. Patients with an Eastern Cooperative Oncology Group performance status <2, adequate renal, hepatic and bone marrow function, and radiologically measurable NPC were eligible. RESULTS: Twenty-five chemonaïve and 27 previously treated patients were enrolled. The overall response rate was 28% [95% confidence interval (CI) 14% to 48%] for the chemonaïve and 48% (95% CI 31% to 66%) for previously treated patients. Toxicities greater than or equal to grade 3 occurred in 15 (60%) chemonaïve and 13 (48%) previously treated patients. Neutropenia was uncommon in chemonaïve patients, but occurred in 37% of previously treated patients. The median time to progression was 3.6 months (range 0.9-7.9) for chemonaïve and 5.1 months (0.9-13.1) for previously treated patients. Median overall survival time was 7.2 months (1.4-15.6) and 10.5 months (2.4-15.0) for chemonaïve and previously treated patients, respectively. CONCLUSIONS: Gemcitabine has moderate activity in NPC with minimal toxicity, and is also an effective salvage agent for patients who have failed or progressed after treatment with other agents.

Adult↗
PubMed2002

Measuring health-related quality of life in Singapore: normal values for the English and Chinese SF-36 Health Survey.

OBJECTIVE: To determine norms for assessing Health-related Quality of Life (HRQOL) in Singapore using the Short Form 36 Health Survey (SF-36). MATERIALS AND METHODS: Mean SF-36 scores were calculated for 24 population subgroups (categorised by age, gender, ethnicity and questionnaire language) and for subjects with self-reported co-morbid conditions using data from a community-based survey in Singapore. RESULTS: The English and Chinese SF-36 was completed by 4122 and 1381 subjects, respectively, 58% (n = 3188) of whom had self-reported co-morbid conditions. SF-36 scores varied in subgroups differing in age, gender and ethnicity. In general, subjects with self-reported co-morbid conditions had lower SF-36 scores than those without these conditions, the magnitude of which exceeded 20 points in several instances. A method for calculation of SF-36 scores adjusted for age, gender, ethnicity and questionnaire language is described. CONCLUSION: We present norms for English and Chinese SF-36 versions in Singapore and describe potential uses for these data in assessing HRQOL in Singapore.

Adult↗
PubMed2002

Angular regression and the detection of the seasonal onset of disease.

BACKGROUND: In examining the seasonality of onset of a disease over the year, investigators attempt to identify the peak of onset, and its magnitude. A second objective is to see if the day in which the disease manifests itself is related to subject-specific characteristics or environmental factors. METHOD: This paper describes appropriate statistical methodology for the situation where seasonality can be summarised by either a single peak or several peaks, possibly determined by patient characteristics or external influences. The circular, rather than linear, nature of the day of onset of a disease (irrespective of year) requires angular regression techniques to assess these relations, and the von Mises distribution replaces the normal distribution in this context. RESULTS: The methods outlined are illustrated by a national study of those experiencing an attack of acute primary angle-closure glaucoma in Singapore. CONCLUSIONS: We recommend re-analyses of already published work on seasonality of disease using this angular methodology. We anticipate that this may provide both useful further insight into aspects of aetiology and case studies for the methods themselves.

Acute Disease↗
PubMed2001

A competing risk approach to the analysis of trials of alternative intra-uterine devices (IUDs) for fertility regulation.

The methods of survival analysis have had a profound influence on the way that studies concerned with the safety and efficacy of intra-uterine devices (IUDs) for fertility control have been designed, conducted, analysed and reported. For example, the Kaplan-Meier technique has been used to summarize the results of controlled clinical trials of alternative devices and the logrank test used to make any comparisons. A particular feature of IUD studies is the large number of possible causes of failure (reasons for discontinuation of the device). These lead to considerations of competing risks, where in this framework, the discontinuations are considered as competing causes of contraceptive failure. In this context, we compare the net and crude probability estimates of discontinuation rates using continuous time and argue for the routine use of the latter. We use data from a randomized multi-centre trialon the long-term safety and efficacy of two IUDs, TCu220C and TCu380A, for illustration.

Contraception↗
PubMed2001

Seasonal variation in breast cancer diagnosis in Singapore.

This study investigates seasonality in the diagnosis of 3219 female breast carcinoma cases reported between 1995-8 in Singapore. There is little evidence of marked seasonal variation. Angular regression suggested that observed differences in peak diagnosis with respect to menopausal status, tumour size, ER and PR status may be chance.

Adult↗
PubMed2001

Competing risks analysis of patients with osteosarcoma: a comparison of four different approaches.

In failure time studies involving a chronic disease such as cancer, several competing causes of mortality may be operating. Commonly, the conventional statistical technique of Kaplan-Meier, which is only meaningfully interpreted by assuming independence of failure types and the censoring mechanism, is employed in clinical research involving competing risks data. Some authors have advocated the use of a cause-specific cumulative incidence function which takes into account the existence of other events within a competing risks framework, without making any assumption about independence. Lunn and McNeil have proposed an approach based on an extension of the Cox proportional hazards regression, which enables direct comparisons between failure types. We have extended this approach to estimate cause-specific cumulative incidence. As it is often not easy to follow competing risks methodology in the literature, this paper sets out systematically the assumptions made and the steps taken to implement four different methods of analysing competing risks data using cumulative incidence rates or the Kaplan-Meier estimates of cause-specific failure probabilities. The data obtained from a randomized trial of patients with osteosarcoma were used to compare these four approaches. As illustrated using the osteosarcoma data, the estimates of the classical Kaplan-Meier methods have larger numerical values than the cause-specific cumulative incidence. On the other hand, estimates of the cause-specific cumulative incidence rates from the conventional method and the modified Cox method are highly comparable.

Adolescent↗
PubMed2001

Evaluating the role of alternative therapy in burn wound management: randomized trial comparing moist exposed burn ointment with conventional methods in the management of patients with second-degree burns.

CONTEXT: Moist exposed burn ointment (MEBO), from China, has been said to revolutionize burn management. OBJECTIVE: Our study was conducted to compare MEBO with conventional management (C) with respect to the rate of wound healing, antibacterial and analgesic effect, and hospital costs. DESIGN: This is a prospective, randomized, controlled clinical trial conducted between 1 March 1997 and 24 October 1998. SETTING: The trial was conducted in a specialized burn facility located in a tertiary referral hospital in a developed and industrialized island-state in Southeast Asia. PATIENTS: We randomly assigned 115 consecutive patients between the ages of 12 and 80 who had partial-thickness thermal burns covering less than 40% of body surface area (BSA) to receive either MEBO or C. Fifty-seven patients were assigned to MEBO and 58 patients to C. The latter group received twice-daily dressing changes; MEBO patients received MEBO every 4 hours. MAIN OUTCOME MEASURES: Patients were hospitalized until 75% BSA had healed. BSA was determined by visual inspection and charted on Lund and Browder charts regularly. Wound healing rate, bacterial infection rate, pain score, and hospitalization costs were recorded. RESULTS: The median time to 75% healing was 17.0 and 20.0 days with MEBO and C, respectively (HR = 0.67, 95% CI = 0.41-1.11, P =.11), suggesting similar efficacy between the 2 modalities. Bacterial infection rates were similar between the 2 groups (HR = 1.10, 95% CI = 0.59-2.03, P =.76). MEBO imparted a greater analgesic effect in the first 5 days of therapy and reduced hospital costs by 8%. CONCLUSIONS: MEBO is as effective as conventional management but is not the panacea for all burn wounds. The use of MEBO eases the management of face and neck burns and facilitates early institution of occupational therapy in hand burns. It confers better pain relief such that fewer opiates are used during the first 5 days after burn injury.

Adult↗
PubMed2001

Seasonality of suicide in Singapore: data from the equator.

BACKGROUND: Studies in the northern and southern hemispheres consistently identify seasonal patterns in suicidal deaths. In many such studies, bimodal yearly peaks have been described for females as against unimodal ones for males. The current study examines the monthly variation in suicidal deaths in Singapore to determine if any seasonal patterns exist in an equatorial region. METHODS: Monthly suicidal death data over the decade 1989-98 were examined for the whole sample and for gender- and age-specific subgroups. Both von Mises' distribution and harmonic analysis techniques were used to interpret the data. RESULTS: Among the 2013 male and 1382 female suicides, there was minimal variation in patterning of suicidal deaths. We found a weak suggestion of a later peak for the females in mid-May as opposed to mid-February for the males, and the peaks for those less than 25 years of age were 5-6 months later than for the older age groups. The magnitude of all peaks was, however, very small suggesting chance variation. The harmonic analyses confirmed that patterning was 'randomly' rather than 'seasonally' determined. CONCLUSION: In an equatorial region, there was no evidence of any 'seasonal' patterning of suicidal deaths.

Adult↗
PubMed2001

A community-based study of scaling assumptions and construct validity of the English (UK) and Chinese (HK) SF-36 in Singapore.

Scaling assumptions and validity of the English (UK) and Chinese (HK) short form 36 health survey (SF-36) were assessed in a community-based survey of 5,503 Chinese, Malays and Indians in Singapore using the international quality of life assessment project approach of item and scale level validation. Missing data for SF-36 items and scales occurred in less than 1.0% of subjects. Item level validation of both versions generally supported assumptions underlying Likert scoring and hypothesised item-order clustering. Item level factor analysis supported the eight-scale structure of the SF-36. In scale level validation, SF-36 scale scores showed wide variability and acceptable internal-consistency reliability (Cronbach's alpha > 0.70 for six English and seven Chinese scales), conformed to hypothesised patterns and generally varied according to hypotheses in subjects known to differ in quality of life. Scale level factor analysis of both versions yielded very similar patterns of factor correlation, comparable to that found in Japan, but differing from that seen in Western populations. Taken together, these results support the validity of the English (UK) and Chinese (HK) SF-36 versions in the multi-ethnic Asian socio-cultural context of Singapore.

Adult↗
PubMed2001

Health-related quality of life of patients with endometrial cancer who are disease-free following external irradiation.

Health-related quality of life (HQoL) is assessed through the patients' own evaluation of the impact that a disease and its treatment may have on some of the physical, psychological and social aspects of their lives. The purpose of this study is to describe the HQoL of patients with endometrial cancer who are free of disease after undergoing external irradiation. An HQoL questionnaire was designed and validated, and consisted of the EORTC QLQ-C30 and 80 additional questions. The patients provided self-reported assessments at the end of radiotherapy, and 1, 3, 6, 12, 18 and 24 months later. Forty-nine out of 66 potential subjects participated in the study, which was confined to the period during which the, women were disease free. Most patients experience physical side effects at the end of treatment and up to 6 months thereafter; 10% of the patients have chronic local symptoms and a large number of the patients think about their treatment even two years later. The patients' overall evaluation of their quality of life is lower than that of a matched population of healthy women.

Adult↗
PubMed2000

Preface.

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Journal Article↗