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Biomedical subjects

David Machin

Publications and source records attributed to David Machin.

At least 37 records · Page 2Linked to original sources
PubMed2004

Early-stage cervical carcinoma, radical hysterectomy, and sexual function. A longitudinal study.

BACKGROUND: Limited knowledge exists concerning the impact of radical hysterectomy (RH) alone on the sexual function of patients with early-stage cervical carcinoma. The authors investigated the longitudinal course of self-reported sexual function after RH. METHODS: The current study was comprised of 173 patients with lymph node-negative, early-stage cervical carcinoma who had undergone RH and pelvic lymphadenectomy. They were assessed prospectively using a validated self-assessment questionnaire 5 weeks and 3 months, 6 months, 12 months, 18 months, and 24 months after RH. Results were compared with an age-matched control group from the general population. RESULTS: Compared with control women, patients experienced severe orgasmic problems and uncomfortable sexual intercourse due to a reduced vaginal size during the first 6 months after RH, severe dyspareunia during the first 3 months, and sexual dissatisfaction during the 5 weeks after RH. A persistent lack of sexual interest and lubrication were reported throughout the first 2 years after RH. Long-term lack of sexual interest and insufficient vaginal lubrication were confirmed by the patient's self-reported changes 12 months after RH compared with before the cancer diagnosis and by a pre-post comparison within patients. However, most of the patients who were sexually active before their cancer diagnosis were sexually active again 12 months after surgery (91%), although with a decrease in sexual frequency reported. CONCLUSIONS: RH had a persistent and negative impact on patients' sexual interest and vaginal lubrication whereas the majority of other sexual and vaginal problems disappeared over time. Sexual and vaginal problems in the short-term and long-term after RH should be discussed with the patient before and after surgery.

Adult↗
PubMed2004

A longitudinal study of pediatric body mass index values predicted health in middle age.

BACKGROUND AND OBJECTIVE: To characterize the use of pediatric body mass index (BMI) to predict obesity, overweight, and diseases in middle age. METHODS: A longitudinal study of people born in a week in 1958 (n=12,327). The main outcome measures are obesity (BMI > or = 30) and overweight (BMI > or = 25) at age 33 and disease history self-reported at age 42. Receiver operating characteristic (ROC) analysis was performed using BMI measured at ages 7, 11, and 16 years as predictors. RESULTS: BMI values measured at age 11 could predict obesity at age 33 with areas under ROC curve (AUC) of 0.78 for males and 0.80 for females (each P < .001). BMI values at age 11 predicted overweight with slightly smaller AUC (each P < .001). They could also predict history of diabetes and hypertension (AUC=0.60 and 0.56, respectively, each P < .01), both sexes pooled. Prediction based on BMI at age 7 was less satisfactory; that at 16 gave limited improvement. Cutoff points based on ROC curves, the international reference, and the 85th and 95th percentiles gave very different profiles of diagnostic features. CONCLUSION: Pediatric BMI may predict adult obesity and overweight with a reasonable profile of sensitivity and specificity.

Adolescent↗
PubMed2004

Are English- and Chinese-language versions of the SF-6D equivalent? A comparison from a population-based study.

OBJECTIVE: The goal of this study was to assess the equivalence of English- and Chinese-language versions of the SF-6D (a 6-dimensional health classification system based on the 36-Item Short Form Health Survey) using a model of equivalence proposed previously. METHODS: We analyzed data from a previously published, cross-sectional, population-based survey of ethnic Chinese in Singapore, using linear regression models to adjust for the influence of potential confounding variables. Based on equivalence clinical trial methods, measurement (ie, scale) and item equivalence were assessed by comparing 90% CIs of differences in scores due to language with predefined equivalence margins, that corresponded to the minimum clinically important difference for SF-6D utility and item scores. RESULTS: Data from 2,558 respondents (aged 21-65 years; 48.8% completed the English-language version) were analyzed. The utility scores of respondents using the English- or Chinese-language versions of the SF-6D had similar distribution patterns, with a mean (SD) utility score of 0.8 (0.12). Adjusted 90% CIs for differences in utility and item scores due to language fell within predefined equivalence margins, suggesting measurement and item level equivalence. The 90% CI for scale scores was -0.0089 to 0.0065 (range, 0.0154; equivalence margin, 0.033); the 90% CI for item scores varied from -0.0046 to -0.0020 (range, 0.0026; equivalence margin, 0.0036) for vitality to -0.0024 to 0.0037 (range, 0.0061; equivalence margin, 0.0088) for social functioning. Functional equivalence was suggested because the various aspects of equivalence proposed previously were demonstrated in this study. CONCLUSIONS: English- and Chinese-language versions of the SF-6D demonstrated item, measurement, and functional equivalence in this population-based study comparing 2 widely used languages with very different linguistic structures. This suggests that English and Chinese SF-6D scores can be pooled, thus increasing the representativeness and power of studies using the SF-6D, and providing a basis for studies to value health by obtaining SF-6D utility scores in Asian populations.

Adult↗
PubMed2004

A randomized controlled trial to compare calcipotriol with betamethasone valerate for the treatment of cutaneous lichen planus.

BACKGROUND: Topical calcipotriol is a vitamin D3 analogue which influences keratinocyte proliferation and differentiation. Its efficacy in cutaneous lichen planus has not been well evaluated. METHODS: This is a randomized open-label trial comparing the effectiveness of calcipotriol 50 microg/g versus betamethasone 0.1% ointments twice daily for 12 weeks in patients with cutaneous lichen planus, with respect to thickness, pigmentation, clearance and pruritus. Patient self-assessment was made at 0, 4, 8 and 12 weeks post randomization using visual analogue scales (VAS). Clinical assessment was made at week 12 and adverse events noted. Clinical response was defined as 75% or more for lesion flattening and absent or minimal pigmentation, and 50% or more for clearance. RESULTS: A total of 31 patients were randomized: 15 to calcipotriol and 16 to betamethasone. Clinically assessed lesion flattening occurred in approximately half the patients. With calcipotriol, there were two responses for pigmentation and one for clearance but none with betamethasone. Patient VAS indicated a gradual improvement in all measures but with little difference between the treatments. The largest difference indicated a 12-point disadvantage to calcipotriol for thickness but this was not statistically significant (p=0.09). Side effects reported were erythema (one patient) and increased pruritus (two patients), all with calcipotriol. CONCLUSION: Calcipotriol appears no more effective than betamethasone. The course of the disease appears to be affected in the same way by both treatments.

Administration, Cutaneous↗
PubMed2004

Ocular biometry and refraction in Mongolian adults.

OBJECTIVE: To describe the variation in ocular biometry and its association with refraction in adult Mongolians. METHODS: The study included 1800 subjects, aged 40 years or more, who were selected in two Mongolian provinces-Hövsgöl and Omnögobi-to participate in this population survey. Axial length (AL) and its components, as well as noncycloplegic autorefraction and corneal power (CP), were measured. RESULTS: Of those selected, 1617 subjects (90.0%) were examined. Mean +/- SD of AL was 23.13 +/- 1.15 mm. There was a very small but significant increase in mean AL with age (0.05 mm per decade, P = 0.03). Autorefraction was performed on 620 of 675 subjects of those examined in Omnögobi. The age and gender standardized prevalences of myopia (< -0.5 D), emmetropia, hyperopia (> +0.5 D), astigmatism (< -0.5 D of cylinder) and anisometropia (>1.0 D difference between eyes) were 17.2%, 49.9%, 32.9%, 40.9%, and 10.7%, respectively. Prevalence of myopia showed no clear trend with increasing age, whereas hyperopia, astigmatism, and anisometropia all increased monotonically. Multiple regression models revealed that AL (P < 0.001) and VCD (P < 0.001) were the strongest determinants of refractive error. CONCLUSIONS: In this cross-sectional study of adult Mongolians, a much lower prevalence of myopia was found than in other East Asian populations studied to date. The mean AL differed little between age groups, in marked contrast to data on Chinese people.

Adult↗
PubMed2003

Longitudinal study of sexual function and vaginal changes after radiotherapy for cervical cancer.

PURPOSE: To investigate the longitudinal course of self-reported sexual function and vaginal changes in patients disease free after radiotherapy (RT) for locally advanced, recurrent, or persistent cervical cancer. MATERIALS AND METHODS: A total of 118 patients referred for RT were included. The patients were assessed, using a validated self-assessment questionnaire, at the termination of RT and 1, 3, 6, 12, 18, and 24 months later. The results were compared with an age-matched control group from the general population. RESULTS: Persistent sexual dysfunction and adverse vaginal changes were reported throughout the 2 years after RT, with small changes over time: approximately 85% had low or no sexual interest, 35% had moderate to severe lack of lubrication, 55% had mild to severe dyspareunia, and 30% were dissatisfied with their sexual life. A reduced vaginal dimension was reported by 50% of the patients, and 45% were never, or only occasionally, able to complete sexual intercourse. Despite sexual dysfunction and vaginal adverse effects, 63% of those sexually active before having cancer remained sexually active after treatment, although with a considerably decreased frequency. CONCLUSIONS: Patients who are disease free after RT for locally advanced, recurrent, or persistent cervical cancer are at high risk of experiencing persistent sexual and vaginal problems compromising their sexual activity and satisfaction.

Adult↗
PubMed2003

Simple clinical prognostic model for hepatocellular carcinoma in developing countries and its validation.

PURPOSE: More than 80% of hepatocellular carcinomas (HCCs) worldwide occur in developing countries, especially in Asia. It often presents at an advanced stage beyond treatment. In this circumstance, a simple prognostic model is useful. Previous prognostic models require radiologic and laboratory investigations that are not readily available in developing countries. Our aim is to formulate and then validate a simple clinical prognostic model for HCC in an Asian population using only clinical parameters and with serum alpha-fetoprotein (AFP) as the sole laboratory test. PATIENTS AND METHODS: Cox regression modeling was performed on several clinical parameters and serum AFP level in 397 patients with HCC who received only supportive care in Singapore. A later group of 324 HCC patients from an Asia-Pacific-wide randomized trial was then used to validate the model. RESULTS: Ascites, physical performance status, and serum AFP were independently predictive of survival. Cox analysis yielded a simple score based on these three variables that categorizes patients into low-, medium-, and high-risk groups with 6-month survivals of 43%, 21%, and 5%, respectively. The prospective validation data provided corresponding estimates of 33%, 15%, and 3% and give confirmation of the utility of the simple model. CONCLUSION: We have formulated and prospectively validated a simple prognostic score for untreated HCC that only requires a clinical evaluation for ascites and physical performance status and measurement of serum AFP. This simple model is particularly apt for developing country circumstances and can also be used to select patients for treatment trials.

Adult↗
PubMed2003

Elicitation of prior distributions for a phase III randomized controlled trial of adjuvant therapy with surgery for hepatocellular carcinoma.

A randomized, controlled clinical trial of radioactive iodine tagged with lipiodol in patients with resected hepatocellular carcinoma was criticized for its early stopping and resulting small sample size. To clarify its results, a new, larger multicenter trial was therefore proposed. This paper describes the elicitation of the pretrial opinions of the investigators involved in the new trial and the construction of appropriate clinical and skeptical prior distributions based on their responses. The prior distributions provide a useful tool in assessing the state of equipoise before the start of the trial. They can also be used in Bayesian analyses, both at the interim stage(s) as well as at the end of the trial. We illustrate these analyses, assuming that the data resulting from the new trial was the same as that obtained in the earlier trial when it was stopped.

Bayes Theorem↗
PubMed2003

Quality of life in an urban Asian population: the impact of ethnicity and socio-economic status.

The relationships between ethnicity, socio-economic status (SES) and health-related quality of life (HRQoL) have not been well characterised in most Asian populations. We therefore studied the influence of ethnicity and SES on HRQoL in a multi-ethnic urban Asian population, adjusting for the influence of other known determinants of HRQoL. In a disproportionately stratified, cross-sectional, population-based survey, Chinese, Malay and Indian subjects in Singapore completed the Short Form 36 Health Survey (SF-36) HRQoL measure and were assessed to determine demographic, socio-economic, psychosocial and other characteristics. Multiple linear regression models were used to study the influence of ethnicity and SES on SF-36 scores while adjusting for the influence of other determinants of HRQoL. The survey participation rate was 92.8%. Ethnic differences in HRQoL were present for all 8 SF-36 scales (p<0.001 for all scales except General Health) among the 4122 Chinese, Malays and Indians surveyed. These ethnic groups also differed in several known determinants of HRQoL (e.g., Chinese had more years of education and Indians had more chronic medical conditions). After adjusting for the influence of these factors, ethnicity and SES independently influenced HRQoL, with mean differences in SF-36 scores due to ethnicity ranging from 1.4 to 13.1 points. Educational level and housing type (markers of SES) were also associated with SF-36 scores (0.5-0.6 point increase per year of education and 3.5-4.0 point increase with better housing type, respectively). Better HRQoL was also associated with better family support, and poorer HRQoL with acute and chronic medical conditions and sick days. The study concludes that ethnicity and SES are associated with clinically important differences in HRQoL in a multi-ethnic, urban Asian population.

Acute Disease↗
PubMed2003

Determinants of intraocular pressure and its association with glaucomatous optic neuropathy in Chinese Singaporeans: the Tanjong Pagar Study.

PURPOSE: To examine the relationship between intraocular pressure (IOP), anthropomorphic, demographic, socioeconomic, systemic, and ocular factors and glaucomatous optic neuropathy (GON) in Chinese people. METHODS: Chinese people (n = 2000), aged 40 to 79 years, were selected from the Singapore electoral register. Of the 1717 considered eligible for examination, 1232 participated, representing a response rate of 71.8%. IOP was estimated with Goldmann applanation tonometry. The drainage angle was assessed with static and dynamic gonioscopy. The optic nerve was examined at high magnification through a dilated pupil with a fundus contact lens or a +78-D lens. Static automated visual field testing was performed on subjects with suspected glaucoma. GON was diagnosed on the basis of structural and functional abnormalities of the optic nerve. RESULTS: The main independent determinants of higher IOP were higher systolic blood pressure (P < 0.001), quadrants of any peripheral anterior synechiae (PAS, P = 0.02) and width of the drainage angle (P = 0.049). A 100- micro m increase in corneal thickness was associated with an increase in mean IOP of 1.5 to 1.8 mm Hg (P < 0.001). Odds of GON increased 1.2 times per 1-mm Hg increase in screening IOP. A clear association between corneal thickness and GON was not identified. CONCLUSIONS: Clinical IOP estimates are related to systolic blood pressure and corneal thickness. Variation in IOP with angle width may suggest that trabecular compaction significantly contributes to causes of the increase in IOP, independent of angle-closure. GON is an IOP-related phenomenon among Chinese Singaporeans.

Adult↗
PubMed2002

Interval cancers following breast cancer screening in Singaporean women.

Our study reports on the interval cancers arising in the subsequent 3 years in women screened as part of the Singapore Breast Cancer Screening Programme that commenced in 1994. Women, the majority of Chinese ethnicity, were either invited or not invited by random allocation to be screened. All women, other than those identified with breast cancer at screening, whether invited or not, were followed for 3 years, and information on all breast cancers arising in this period was obtained through the national registry. In particular, the cancers arising from those women who were deemed free of the disease at screening were noted. The mammographs taken at screening of those women who developed such an interval cancer were rereviewed by 3 radiologists. In the 28,099 women who were screened and deemed free of disease, 59 interval cancers were reported with annual rates of 2.1, 10.6 and 10.8 per 10,000 women-years in the succeeding 3-year periods. In 39,425 women who were invited but declined screening, the rates were 17.0, 15.5 and 11.7, while the corresponding rates from 97,294 women not invited were 12.8, 13.3 and 13.0. Whereas the annual incidence at 1 year in women who have been screened is much lower than those in the 2 groups who were not screened, it is of a similar magnitude by 2 years. This suggests that locally an optimal screening interval may be close to 1 year. The rereview of the mammograms of those 59 women with interval cancers suggested that the maximum possible number of these that might have been detected at screening was 10 (17%).

Aged↗
PubMed2002

On the issue of 'multiple' first failures in competing risks analysis.

In the classical competing risks framework, a subject may only fail from one of several distinct causes. However, in the context of cancer clinical trials where information on first relapse is usually of interest, there could be occasions when 'multiple' first recurrences are identified at a particular follow-up. In this instance, the competing risks methodology cannot be implemented without first tackling the issue of 'tied' first failure. When the tied events were substantial, Arriagada et al. regarded each competing failure separately, and combined the 'simultaneous' failures into a single category for analysis. This paper describes two other methods of accounting for 'multiple' failures. First, the ties were dealt with by applying a weighting factor which was equal to the reciprocal of the number of ties. We also considered 'jittering' which randomly adds or subtracts a small number to each 'tied' event time to randomly break the tie. As illustrated using the data obtained from a randomized trial of patients with operable osteosarcoma, the estimates based on Arriagada's approach have larger standard errors. Estimates from the other alternative methods were similar. Multiple jittering has the advantage of wide applicability in any situation of tied survival times. However, it takes a longer computer running time, especially when the number of replicates is large. The weighted Cox approach is the method of choice where statistical software allows its implementation without extra programming effort.

Antineoplastic Agents↗
PubMed2002

Bayesian two-stage designs for phase II clinical trials.

Many different statistical designs have been used in phase II clinical trials. The majority of these are based on frequentist statistical approaches. Bayesian methods provide a good alternative to frequentist approaches as they allow for the incorporation of relevant prior information and the presentation of the trial results in a manner which, some feel, is more intuitive and helpful. In this paper, we propose two new Bayesian designs for phase II clinical trials. These designs have been developed specifically to make them as user friendly and as familiar as possible to those who have had experience working with two-stage frequentist phase II designs. Thus, unlike many of the Bayesian designs already proposed in the literature, our designs do not require a distribution for the response rate of the currently used drug or the explicit specification of utility or loss functions. We study the properties of our designs and compare them with the Simon two-stage optimal and minimax designs. We also apply them to an example of two recently concluded phase II trials conducted at the National Cancer Centre in Singapore. Sample size tables for the designs are given.

Antimetabolites, Antineoplastic↗
PubMed2002

The equivalence of English and Chinese SF-36 versions in bilingual Singapore Chinese.

OBJECTIVE: To assess the equivalence of English and Chinese versions of the SF-36. METHODS: Using a crossover design with block randomisation and stratification by age, identical English or Chinese questionnaires containing the English (UK) and Chinese (HK) SF-36 versions were administered 3-16 days apart to 168 free-living, bilingual, ethnic Chinese volunteers in Singapore. Item level equivalence of both versions was assessed by comparing item means and orderings within each scale. Scale level equivalence was assessed by comparing internal consistency (Cronbach's alpha), results of factor analysis and mean scale scores (using paired t-tests and intra-class correlations). RESULTS: Item and scale level comparisons supported the equivalence of both versions. For both the versions, item means, item ordering and Cronbach's alpha were similar, and factor analysis yielded two factors with similar factor loadings. There was no clinically important difference in mean scale scores for seven of eight scales, and intra-class correlations were excellent/good for five scales (0.69-0.77) and moderate for three scales (0.55-0.57). CONCLUSION: English (UK) and Chinese (HK) SF-36 versions are equivalent in bilingual Singapore Chinese. Our data suggest that SF-36 scores from English- and Chinese-speaking subjects may be combined in studies using the SF-36, increasing the power and representativeness of such studies.

Adolescent↗
PubMed2002

High-dose tamoxifen in the treatment of inoperable hepatocellular carcinoma: A multicenter randomized controlled trial.

In the Asia-Pacific region and elsewhere, almost 85% of patients with hepatocellular carcinoma (HCC) are inoperable at diagnosis and have a dismal prognosis. Tamoxifen (TMX) is believed to inhibit HCC positive for estrogen receptor (ER), but most HCCs are ER negative. Results of previous phase 3 trials in inoperable HCC have been conflicting and inconclusive. At higher doses, however, TMX inhibits HCC through ER-independent mechanisms. A multicenter randomized controlled trial was performed to assess the role of high-dose TMX versus placebo (P) in the treatment of patients with inoperable HCC with respect to survival and quality of life (QoL). A total of 329 patients from 10 centers in 9 countries in the Asia-Pacific region enrolled in a double-blind randomized controlled trial of TMX 120 mg/d (TMX120) against P as a control arm with an intermediate dosage of TMX 60 mg/d (TMX60) to assess possible dose response. An independent data monitoring committee reviewed all aspects of the trial. QoL was assessed using the European Organization for Research and Treatment of Cancer QLQ-C30 questionnaire. Three-month survival rates for the P, TMX60, and TMX120 groups were 44%, 41%, and 35%, respectively, with a statistically significant trend difference in survival across the 3 treatment regimens (P =.011). There was a significantly higher risk of death in the TMX120 group compared with the P group (hazard ratio, 1.39; 95% confidence interval, 1.07-1.81). Adverse drug reactions were reported in 3% (9 patients), and 8 patients were lost to follow-up. In conclusion, TMX does not prolong survival in patients with inoperable HCC and has an increasingly negative impact with increasing dose. No appreciable advantage to QoL with TMX was observed.

Adolescent↗