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S W Duffy

Publications and source records attributed to S W Duffy.

At least 37 records · Page 2Linked to original sources
PubMed2003

Assessing progression and efficacy of treatment for diabetic retinopathy following the proliferative pathway to blindness: implication for diabetic retinopathy screening in Taiwan.

AIMS: The natural history and treatment efficacy of diabetic retinopathy (DR) play important roles in the evaluation of screening. Therefore, the natural history of DR and rates of transition after treatment (including metabolic control and laser photocoagulation) from no diabetic retinopathy (NDR) to blindness were quantified. METHODS: We studied a cohort of 795 patients with diabetes mellitus (DM) receiving fundus examination in the ophthalmology out-patient department of one medical centre between 1 January 1990 and 31 December 1992 in Taiwan. Follow-up data until 31 December 1998 were collected by chart review. Two multistate Markov models were proposed to assess the efficacy of the treatment regime in reducing progression to blindness. RESULTS: The average times spent in states (i) no diabetic retinopathy (NDR), (ii) background diabetic retinopathy (BDR), (iii) preproliferative diabetic retinopathy (PPDR), and (iv) proliferative retinopathy (PDR) were 10.86 years, 8.33 years, 1.67 years, and 2.17 years, respectively. Early detection of PPDR may lead to a 60% reduction in PDR and an 83% reduction in blindness. Simulated results based on these parameters show that an annual screening programme, a biennial screening regime and a 4-yearly screening regime can lead to 54% (95% confidence interval (CI): 44-62%), 51% (95% CI: 41-59%), and 46% (95% CI: 36-54%) reductions in blindness, respectively. CONCLUSIONS: Assessing the progression of DR following the proliferative pathway in this study suggests that screening for DR is worthwhile and that a 4-year interscreening interval for patients as yet without DR may be justified.

Adult↗
PubMed2003

Radiology review of the UKCCCR Breast Screening Frequency Trial: potential improvements in sensitivity and lead time of radiological signs.

AIM: To review all previous mammograms of breast cancer cases diagnosed during a randomized trial comparing 3 yearly to annual mammographic screening with a view to identifying and quantifying cases that might potentially have been diagnosed earlier. METHODS: Mammograms of 602 breast cancer cases (399 screen-detected and 203 interval cases) were reviewed in chronological order and suspicious radiological features noted for each mammogram, up to and including the diagnostic mammogram. RESULTS: Of the 602 cases, 79 (13%) had features at diagnosis that were visible on previous mammograms, suggesting a sensitivity of interpretation of 87%. A similar proportion of screen-detected (14%) and interval cancers (11%) had signs at diagnosis that were visible on previous mammograms. The potential for improvement was particularly noted for asymmetric density (sensitivity = 77%, average time visible before diagnosis 14 months) and parenchymal deformity/stellate lesion (sensitivity = 81%, average time visible before diagnosis 12 months). CONCLUSION: The highest sensitivity was observed for comedo-type microcalcifications (sensitivity = 97%, average time visible before diagnosis 5 months). By improvements in sensitivity to asymmetric density and parenchymal deformity/stellate lesion, 4% of tumours could have their time of diagnosis advanced substantially.

Adult↗
PubMed2003

A potentially useful distribution model for dietary intake data.

BACKGROUND: Conventional mixed models for the analysis of diet diary data have introduced several simplifying assumptions, such as that of a single standard deviation for within-person day-to-day variation which is common to all individuals. OBJECTIVE: We developed a model in which the within-person standard deviation was allowed to differ from person to person. DESIGN: The model was demonstrated using data on daily retinol intake from the Dietary and Nutritional Survey of British Adults. The data were from 7-day weighed dietary diaries. Estimation was performed by Markov chain Monte Carlo. Reliability of the model was assessed from the accuracy of estimation of the percentage of days on which various intakes were exceeded. For levels above the median retinol intake, estimation of percentages of days with excessive intakes was most accurate using the model with varying within-person standard deviation. SETTING: A survey of British adults aged 16-64 years. SUBJECTS: In total 2197 adults living in the UK, 1087 males and 1110 females. RESULTS: Under the traditional model, estimated daily intake ranged from 716.4 to 1421.8 microg depending on age and sex, with a within-person standard deviation of 4298.9 microg. Under the new model, estimated average daily intake ranged from 388.9 to 518.3 microg depending on age and sex, but with a within-person standard deviation varying between subjects with a 95% range of 29 to 8384 microg. The new model was shown to predict the percentage of days of exceeding large intakes more successfully than the traditional model. For example, the percentage of days of exceeding the maximum recommended intake (9000 microg for men and 7500 microg for women) was 2.4%. The traditional model predicted no excessive intakes, whereas the new model predicted 2.9%. CONCLUSIONS: This model is potentially useful in dietary research in general and for analysis of data on chemical contaminants in foods, in particular.

Adolescent↗
PubMed2003

The Swedish Two-County Trial of mammographic screening: cluster randomisation and end point evaluation.

BACKGROUND: The Swedish Two-County Trial has been criticised on the grounds of the cluster randomisation and alleged bias in classification of cause of death. PATIENTS AND METHODS: In the Two-County Trial, 77 080 women were randomised to regular invitation to screening (active study population, ASP) and 55 985 to no invitation (passive study population, PSP), in 45 geographical clusters. After approximately 7 years, the PSP was invited to screening and the trial closed. We analysed data using hierarchical statistical models to take account of cluster randomisation, and performed a conservative analysis assuming a systematic difference between ASP and PSP in baseline breast cancer mortality in one of the counties. We also analysed deaths from causes other than breast cancer and from all causes among breast cancer cases diagnosed in the ASP and PSP. RESULTS: Taking account of the cluster randomisation there was a significant 30% reduction in breast cancer mortality in the ASP. Conservatively, assuming a systematic difference between ASP and PSP clusters in baseline breast cancer mortality, there was a significant 27% reduction in mortality in the ASP. Ignoring classification of cause of death, there was a significant 13% reduction in all-cause mortality in breast cancer cases in the ASP. CONCLUSIONS: Breast cancer mortality is a valid end point and mammographic screening does indeed reduce mortality from breast cancer. The criticisms of the Swedish Two-County Trial are unfounded.

Adult↗
PubMed2002

Quantification of the effect of mammographic screening on fatal breast cancers: The Florence Programme 1990-96.

Breast cancer cases diagnosed in women aged 50-69 since 1990 to 1996 in the City of Florence were partitioned into those who had been invited to screening prior to diagnosis and those who had not. All cases were followed up for vital status until 31 December 1999. The cumulative number of breast cancer deaths among the cases were divided by screening and invitation status, to give the rates of cancers proving fatal within a period of 8 years of observation (incidence-based mortality). We used the incidence-based mortality rates for two periods (1985-86, 1990-96), pre and during screening. The incidence-based mortality ratio comparing 1990-96 and 1985-86 was 0.50 (95% CI : 0.38-0.66), a significant 50% reduction. For noninvited women, compared to 1985-86, there was a 41% significant mortality reduction (RR=0.59, 95% CI : 0.42-0.82). The comparable reduction in those invited was a significant 55% (RR=0.45, 95% CI : 0.32-0.61). The incidence ratio of rates of cancers stage II or worse was close to one when the noninvited in 1990-96 were compared with 1985-86 (RR=0.97, 95% CI : 0.78-1.21). Excluding prevalent cases, the rate of stage II+ breast cancer cases was 42% lower in Screened women compared with the noninvited (RR=0.58, 95% CI : 0.45-0.74). This study confirmed that new treatments and the first rounds of the screening programme contributed to reducing mortality from breast cancer.

Aged↗
PubMed2002

Estimates of the likely prophylactic effect of tamoxifen in women with high risk BRCA1 and BRCA2 mutations.

The development of breast cancer control strategies in women at high genetic risk of breast cancer is an important issue. The likely benefit of chemopreventive approaches is of particular interest. Tamoxifen tends to be more effective in both prevention and treatment of oestrogen receptor positive tumours than oestrogen receptor negative. In this study, we combine the oestrogen-receptor specific effects of tamoxifen from randomized preventive or therapeutic trials with the oestrogen receptor status of tumours in BRCA1 and BRCA2 mutation positive women from published tumour surveys to obtain estimates of the likely effect of tamoxifen administration in mutation carriers. We used a simple two-stage procedure to estimate the benefit as a weighted average of the effect on oestrogen receptor positive tumours and oestrogen receptor negative, and using a more complex hierarchical modelling approach. Using the simple procedure and deriving the estimates of benefit from both primary prevention and therapeutic trials, we obtain an estimated reduction in risk of breast cancer from administration of tamoxifen in BRCA1 mutation positive women of 13% (RR=0.87, 95% CI 0.68--1.11). The corresponding estimated reduction in BRCA2 mutation positive women was 27% (RR=0.73, 95% CI 0.59--0.90). Using the more complex models gave essentially the same results. Using only the primary prevention trials gave smaller estimates of benefit in BRCA1 carriers but larger estimates in BRCA2, in both cases with wider confidence intervals. The benefit of prophylactic use of tamoxifen in BRCA1 mutation carriers is likely to be modest, and the effect in BRCA2 mutation carriers somewhat greater.

Adult↗
PubMed2002

Deterministic models for breast cancer progression: application to the association between mammographic parenchymal pattern and histologic grade of breast cancers.

Dense mammographic patterns are a risk factor for breast cancer. In a recent case-control study, dense patterns were observed to be associated with a higher relative risk estimate for the more aggressive grade 3 tumors than for grade 1 or 2 tumors. The present study was designed to ascertain, by reference to odds ratio estimates of relative risk by tumor size and histologic grade, whether this was more likely to be due to increased innate predisposition of dense parenchymal patterns to grade 3 tumors, or to dedifferentiation of cases missed at screening due to dense patterns. If the observation were due entirely to dedifferentiation, then for a given size the relative risk of grade 3 tumors would be the same as for grades 1-2. Size-specific relative risks of grade 3 tumors were higher than those of grade 1-2 tumors. It is concluded that the majority of the enhanced risk of grade 3 tumors is due to enhanced innate predisposition to grade 3 tumors in dense breasts.

Adult↗
PubMed2002

Probabilities of progression of aortic aneurysms: estimates and implications for screening policy.

BACKGROUND: Screening for abdominal aortic aneurysm, and intervention with elective repair, can reduce the incidence of aneurysmal rupture by a half. If a screening programme is implemented, it is essential to determine appropriate follow up intervals for rescreening. This paper estimates probabilities of progression growth of aortic diameter to provide evidence for this. METHODS: Data were taken from 2342 men aged 65-80 screened in the Chichester randomised control trial, who have been followed up for an average of 11 years. Aortic diameter was modelled as a Markov process with four categories: <30 mm (normal), 30-44 mm, 45-54 mm, and > or =55 mm. Estimates of the probabilities of progressing to each higher category were obtained. RESULTS: The probabilities of progression increased with greater initial aortic diameter. The estimated rates/year were 0.018 (95% confidence interval 0.014 to 0.023), 0.16 (0.12 to 0.20), and 0.49 (0.35 to 0.70) respectively for moving up one category. The probabilities of moving from <30 mm to > or =55 mm were estimated as 1% in 5 years and 12% in 15 years, while the corresponding figures for moving from 45-54 mm to > or =55 mm were 91% and 99%. There were differences in rates of progression according to age, with men over 70 years having rates about three times those of men under 70. CONCLUSIONS: It seems unnecessary to follow up men with normal aortic diameter as they experience a low probability of reaching criteria for surgery even within 15 years. However, follow up intervals should be progressively shorter for those with greater aortic diameter, especially in those aged over 70. Active follow up, for example every 3 months, is appropriate for men with an aortic diameter of 45-54 mm.

Aged↗
PubMed2002

All-cause mortality among breast cancer patients in a screening trial: support for breast cancer mortality as an end point.

BACKGROUND: It has recently been suggested that all-cause mortality is a more appropriate end point than disease specific mortality in cancer screening trials, and that disease specific mortality is biased in favour of screening. This suggestion is based partly on supposed inconsistencies between all-cause mortality results and disease specific results in cancer screening trials, and alleged increases in deaths from causes other than breast cancer among breast cancer cases diagnosed among women invited to screening. METHODS: We used data from the Swedish Two-County Trial of mammographic screening for breast cancer, in which 77 080 women were randomised to an invitation to screening and 55 985 to no invitation. We estimated relative risks (RRs) (invited v control) of death from breast cancer, death from other causes within the breast cancer cases, and death from all causes within the breast cancer cases. RRs were adjusted for age and took account of the longer follow up of breast cancer cases in the invited group due to lead time. RESULTS: There was a significant 31% reduction in breast cancer mortality in the invited group (RR 0.69, 95% confidence interval (CI) 0.58-0.80; p<0.001). There was no significant increase in deaths from other causes among breast cancer cases in the invited group (RR 1.12, 95% CI 0.96-1.31; p=0.14). A significant 19% reduction in deaths from all causes was observed among breast cancer cases in the group invited to screening (RR 0.81, 95% CI 0.72-0.90; p<0.001). A more conservative estimation gave a significant 13% reduction (RR 0.87, 95% CI 0.78-0.97; p=0.01). These findings are consistent with the magnitude of the reduction in breast cancer mortality. CONCLUSIONS: Invitation to screening was associated with a reduction in deaths from all causes among breast cancer cases, consistent with high participation rates in screening. There is no significant evidence of bias in cause of death classification in the Two-County Trial, and as breast cancer mortality is the targeted clinical outcome in breast cancer screening, it is the appropriate end point in a breast cancer screening trial. All-cause mortality is a poor and inefficient surrogate for breast cancer mortality.

Adult↗
PubMed2002

Cross-issue synthesis: potential application to breast cancer, tamoxifen and genetic susceptibility.

BACKGROUND: Cross-design synthesis usually refers to the inclusion in a meta-analysis of studies addressing the same question but using different designs, for example, combining results from randomised trials with those from case-control studies. Here we describe a procedure for combining information from studies addressing different but clinically related questions, referred to, for brevity, as cross-issue synthesis. METHODS: Surveys have measured the oestrogen receptor (ER) status of invasive breast cancer in women with mutations in the BRCA1 or BRCA2 gene. These mutations confer a substantially increased risk of breast cancer. These are also published randomised trials of tamoxifen administered for at least 3 years, either as an adjuvant therapy or for primary prevention, which record whether breast cancer recurred or occured respectively. These studies also give results by ER status. There are biological reasons to suppose that tamoxifen is more effective at preventing ER-positive cancers, and may have little or no effect at preventing ER-negative cancers. Women with BRCA mutations are more likely to develop ER-negative cancers. Combining meta analyses for these two types of studies supplies an estimate of the effectiveness of tamoxifen in preventing breast cancer in women with BRCA mutation. Hierarchical models were developed for this purpose. Estimation was by Markov chain Monte Carlo (MCMC). RESULTS: A range of models were fitted by MCMC. Using these, the effect of tamoxifen on the relative risk of developing breast cancer in women with a mutation in the BRCA1 gene is estimated to be 0.90 95% confidence interval (CI) (0.52, 1.61), and for the BRCA2 gene 0.71 95% CI (0.45, 1.21). DISCUSSION: This procedure can be generalised to combine information from two sets of studies addressing different, but clinically related questions.

Antineoplastic Agents, Hormonal↗
PubMed2001

Randomization at the level of primary care practice: use of pre-intervention data and random effects models.

The Anglia menorrhagia education study tests the effectiveness of an education package for the treatment of menorrhagia given to doctors at a primary care level. General practices were randomized to receive or not receive the package. It is hoped that this intervention will reduce the proportion of women suffering from menorrhagia that are referred to hospital. Data are available on the treatment and referral of women in the practices in the education and control groups, both pre- and post-intervention. We define and demonstrate a random effects logistic regression model that includes pre-intervention data for calculating the effectiveness of the intervention.

Female↗
PubMed2001

Beyond randomized controlled trials: organized mammographic screening substantially reduces breast carcinoma mortality.

BACKGROUND: The efficacy of mammographic screening in the reduction of breast carcinoma mortality has been demonstrated in randomized controlled trials. However, the evaluation of organized screening outside of research settings (so-called "service screening") faces unique methodologic and conceptual challenges. The current study describes the evaluation of organized mammography screening in a clinical setting and demonstrates the benefit obtained from service screening in two Swedish counties. METHODS: In the group of subjects ages 20--69 years, there were 6807 women diagnosed with breast carcinoma over a 29-year period in 2 counties in Sweden and 1863 breast carcinoma deaths. All patients were classified from patient charts based on their screening status (i.e., whether they had been invited to undergo screening and whether they actually had undergone screening). The number of women who lived in the 2 counties during the 29-year study period was provided by the Central Bureau of Statistics. Breast carcinoma-specific mortality was compared across three time periods: 1) 1968--1977, when no screening was taking place because mammography had not been introduced; 2) 1978--1987, the approximate period of the Two-County randomized controlled trial of screening in women ages 40--74 years; and 3) 1988--1996, when all women in the 2 counties ages 40--69 years were invited to undergo screening (service screening). When comparing breast carcinoma mortality in screened women with that in women diagnosed before screening was introduced, a correction for self-selection bias was incorporated to prevent overestimation of the benefit of screening. RESULTS: The mortality from incident breast carcinoma diagnosed in women ages 40-69 years who actually were screened during the service screening period (1988--1996) declined significantly by 63% (relative risk [RR] = 0.37; 95% CI, 0.30--0.46) compared with breast carcinoma mortality during the time period when no screening was available (1968--1977). The mortality decline was 50% (RR = 0.50; 95% CI, 0.41--0.60) when breast carcinoma mortality among all women who were invited to undergo screening (nonattendees included) was compared with breast cancer mortality during the time period when no screening was available (1968--1977). The reduction in mortality observed during the service screening period, adjusted for selection bias, was 48% (RR = 0.52; 95% CI, 0.43--0.63). No significant change in breast carcinoma mortality was observed over the three time periods in women who did not undergo screening. This group included women ages 20--39 years because these individuals were never invited to undergo screening, and women ages 40--69 years who did not undergo screening (not invited during the randomized trial or invited during the second and third time periods but declined). CONCLUSIONS: Regular mammographic screening resulted in a 63% reduction in breast carcinoma death among women who actually underwent screening. The policy of invitation to organized screening with mammography appears to have reduced breast carcinoma mortality by 50% in these 2 counties.

Adult↗
PubMed2001

Learning preferences, computer attitudes, and test performance with computer-aided instruction.

BACKGROUND: Learning preference refers to how individuals choose to approach learning situations. Computer-aided instruction (CAI) permits the adaptation of educational content to individual student learning strategies. METHODS: To determine if learning preference and computer attitude influence the acquisition of knowledge using CAI materials, a prototype CAI program was developed that incorporated differing learning exercises. Students (n = 180) completed Rezler's Learning Preference Inventory (LPI) and a computer attitude survey (CAS). The LPI uses three sets of paired scales to characterize learning preference and choice of learning situation. The CAS assesses student attitudes toward computers in general (CAS-G), as well as the educational use of computers (CAS-E). After finishing the program students completed a program attitude survey (CAS-P). Immediate comprehension was assessed by pretests and posttests incorporated into the program. Retention was assessed by a repeat of the posttest 4 to 6 weeks after initial program review. RESULTS: Scores (mean +/- SEM) on the pretest, posttest, and late posttest were 38.1% +/- 1.35%, 70.9% +/- 1.24%, and 62.5% +/- 1.44%, respectively. There was no correlation between students' learning preferences or computer attitude and test performance. CONCLUSIONS: The data indicate that CAI provides a means of delivering educational content that results in an increase in knowledge that is not correlated with computer attitudes or learning preferences.

Angiography↗
PubMed2001

Risk factors for and relationship between bacterial vaginosis and cervicitis in a high risk population for cervicitis in Southern Iran.

In 1990, a study of the reproductive habits and cervical pathology in women of the Qashgha'i nomadic tribe, resulted in a high prevalence of cervicitis. This led us to explore the likely infectious agents responsible for a such high prevalence; to assess the difference in cervicitis rates between nomadic and non-nomadic populations in the same area; and to determine the risk factors for and the relationship between cervicitis and bacterial vaginosis (BV). In 1996-1997 a study was carried out of 839 married women of the Qashgha'i, 274 of the Lor nomadic tribes, and 388 non-nomadic urban women. A gynaecological examination, Pap smear and vaginal secretion for assessing BV by gram staining were performed. Data was analysed by logistic regression. Backward stepwise regression was used to assess multivariable effects on risk of cervicitis. The prevalence of cervicitis was 88% in the Qashgha'i, 85% in the Lor and 71% in the urban population. In the multivariate backward stepwise regression analysis for predictors of cervicitis in the Qashgha'i, significant factors were decreased association with those over 40 (p < 0.004) and postpartum bleeding. In the Lor tribe the predictors were an increased risk after more than four pregnancies (p < 0.01) and the use of contraception. Among the urban population, the risk of cervicitis was increased with the use of oral contraceptive previously (p < 0.03) or currently (p < 0.01). BV was strongly associated with cervicitis, with a relatively high attributable risk. Both sexual and childbirth exposures may be associated with cervicitis in these populations.

Adult↗
PubMed2001

The long-term benefits of a single scan for abdominal aortic aneurysm (AAA) at age 65.

AIM: To investigate the efficacy of a single ultrasonic scan at age 65 to identify patients at risk from ruptured abdominal aortic aneurysm (AAA). METHOD: A total of 6058 men aged 64-81 were recruited to a randomised trial, and 3000 were invited to attend a single screening test. An additional population of 1011 men was offered screening as they reached age 65. If a normal aorta was identified in this sub-group, further scans were offered at two-yearly intervals. Follow up and treatment of those identified as having an aortic dilatation of 3 cm or greater was undertaken. All subject groups were monitored for deaths occurring over the study period, and date and cause of death were recorded. RESULTS: A total of 2212 men attended screening in the randomised trial; the overall compliance was 74%, and prevalence of AAA was 7.7%. Compliance decreased, and prevalence increased, with age. Mortality from ruptured AAA was reduced by 68% at 5 years (screened group compared to the age-matched control population), and by 42% in the study arm (screened and refusers) compared with controls. The benefit persisted at ten years (53% and 21% respectively). Of the uncontrolled sample of 1011 men offered a scan at age 65, 681 attended and 649 of these were found to have a normal aortic diameter; re-screening demonstrated new aneurysm development in 4% over ten years. The aortic diameters of the new AAAs were under 4 cm and would therefore have a low risk of rupture.1 Mortality from rupture in all those with an initially normal aortic diameter was low, at 1 case per 1000 scans over ten years. CONCLUSION: Screening once for AAA at age 65 can identify the majority of AAA that are of clinical significance and can identify a large population at low risk from rupture who do not require surveillance. This policy has been effective when combined with selective treatment in reducing the risk of rupture for ten years in those who attend the screening programme.

Aged↗
PubMed2001

Dietary intake of soybean protein and menstrual cycle length in pre-menopausal Singapore Chinese women.

BACKGROUND: Intake of soybean protein was associated with a reduced risk of breast cancer in a case-control study. It has also been demonstrated to increase menstrual cycle length in an experimental setting. OBJECTIVE: To ascertain whether the association of soybean protein intakes with menstrual cycle length persists in an uncontrolled community setting. DESIGN: Cross-sectional food frequency dietary survey, menstrual cycle survey and prospective collection of menstrual cycle data. SETTING: A hospital clinic and a nursing college. SUBJECTS: Two hundred menstruating women. RESULTS: An association (P = 0.034) of higher intakes of soybean protein with increased menstrual cycle length, as recorded by self report and by prospectively recording three consecutive cycles, was observed. The risk of menstrual cycle length being greater than the median, when comparing the upper quartile (8.7-35.2 g x day(-1)) of soybean intake and the lowest quartile (0.1-3.3 g x day(-1)) was double, and this approached statistical significance (OR = 2.02, 95% CI = 0.88-4.64 and OR = 1.93, 95% CI = 0.82-4.56 for self-reported cycle length and cycle length as recorded by diary, respectively). In terms of the absolute association with cycle length, subjects in the upper quartile of soybean intake demonstrated a cycle length 1-2 days longer than did subjects in the lowest quartile. CONCLUSIONS: It is likely that the association between dietary intake of soybean protein and length of menstrual cycle prevails in the community setting. This is shown using both self-reported cycle length and cycle length as recorded in a prospective diary.

Adult↗