Alicja R. Rudnicka
St George's, University of London
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Featured researches published by Alicja R. Rudnicka.
BMJ | 2003
Malcolm Law; Nicholas J. Wald; Alicja R. Rudnicka
Abstract Objectives To determine by how much statins reduce serum concentrations of low density lipoprotein (LDL) cholesterol and incidence of ischaemic heart disease (IHD) events and stroke, according to drug, dose, and duration of treatment. Design Three meta-analyses: 164 short term randomised placebo controlled trials of six statins and LDL cholesterol reduction; 58 randomised trials of cholesterol lowering by any means and IHD events; and nine cohort studies and the same 58 trials on stoke. Main outcome measures Reductions in LDL cholesterol according to statin and dose; reduction in IHD events and stroke for a specified reduction in LDL cholesterol. Results Reductions in LDL cholesterol (in the 164 trials) were 2.8 mmol/l (60%) with rosuvastatin 80 mg/day, 2.6 mmol/l (55%) with atorvastatin 80 mg/day, 1.8 mmol/l (40%) with atorvastatin 10 mg/day, lovastatin 40 mg/day, simvastatin 40 mg/day, or rosuvastatin 5 mg/day, all from pretreatment concentrations of 4.8 mmol/l. Pravastatin and fluvastatin achieved smaller reductions. In the 58 trials, for an LDL cholesterol reduction of 1.0 mmol/l the risk of IHD events was reduced by 11% in the first year of treatment, 24% in the second year, 33% in years three to five, and by 36% thereafter (P < 0.001 for trend). IHD events were reduced by 20%, 31%, and 51% in trials grouped by LDL cholesterol reduction (means 0.5 mmol/l, 1.0 mmol/l, and 1.6 mmol/l) after results from first two years of treatment were excluded (P < 0.001 for trend). After several years a reduction of 1.8 mmol/l would reduce IHD events by an estimated 61%. Results from the same 58 trials, corroborated by results from the nine cohort studies, show that lowering LDL cholesterol decreases all stroke by 10% for a 1 mmol/l reduction and 17% for a 1.8 mmol/l reduction. Estimates allow for the fact that trials tended to recruit people with vascular disease, among whom the effect of LDL cholesterol reduction on stroke is greater because of their higher risk of thromboembolic stroke (rather than haemorrhagic stroke) compared with people in the general population. Conclusions Statins can lower LDL cholesterol concentration by an average of 1.8 mmol/l which reduces the risk of IHD events by about 60% and stroke by 17%.
Computer Methods and Programs in Biomedicine | 2012
Muhammad Moazam Fraz; Paolo Remagnino; Andreas Hoppe; Bunyarit Uyyanonvara; Alicja R. Rudnicka; Christopher G. Owen; Sarah Barman
Retinal vessel segmentation algorithms are a fundamental component of automatic retinal disease screening systems. This work examines the blood vessel segmentation methodologies in two dimensional retinal images acquired from a fundus camera and a survey of techniques is presented. The aim of this paper is to review, analyze and categorize the retinal vessel extraction algorithms, techniques and methodologies, giving a brief description, highlighting the key points and the performance measures. We intend to give the reader a framework for the existing research; to introduce the range of retinal vessel segmentation algorithms; to discuss the current trends and future directions and summarize the open problems. The performance of algorithms is compared and analyzed on two publicly available databases (DRIVE and STARE) of retinal images using a number of measures which include accuracy, true positive rate, false positive rate, sensitivity, specificity and area under receiver operating characteristic (ROC) curve.
PLOS ONE | 2011
Ma’en Obeidat; Louise V. Wain; Nick Shrine; Noor Kalsheker; María Soler Artigas; Emmanouela Repapi; Paul R. Burton; Toby Johnson; Adaikalavan Ramasamy; Jing Hua Zhao; Guangju Zhai; Jennifer E. Huffman; Veronique Vitart; Eva Albrecht; Wilmar Igl; Anna-Liisa Hartikainen; Anneli Pouta; Gemma Cadby; Jennie Hui; Lyle J. Palmer; David Hadley; Wendy L. McArdle; Alicja R. Rudnicka; Inês Barroso; Ruth J. F. Loos; Nicholas J. Wareham; Massimo Mangino; Nicole Soranzo; Tim D. Spector; Sven Gläser
Rationale Lung function measures are heritable traits that predict population morbidity and mortality and are essential for the diagnosis of chronic obstructive pulmonary disease (COPD). Variations in many genes have been reported to affect these traits, but attempts at replication have provided conflicting results. Recently, we undertook a meta-analysis of Genome Wide Association Study (GWAS) results for lung function measures in 20,288 individuals from the general population (the SpiroMeta consortium). Objectives To comprehensively analyse previously reported genetic associations with lung function measures, and to investigate whether single nucleotide polymorphisms (SNPs) in these genomic regions are associated with lung function in a large population sample. Methods We analysed association for SNPs tagging 130 genes and 48 intergenic regions (+/−10 kb), after conducting a systematic review of the literature in the PubMed database for genetic association studies reporting lung function associations. Results The analysis included 16,936 genotyped and imputed SNPs. No loci showed overall significant association for FEV1 or FEV1/FVC traits using a carefully defined significance threshold of 1.3×10−5. The most significant loci associated with FEV1 include SNPs tagging MACROD2 (P = 6.81×10−5), CNTN5 (P = 4.37×10−4), and TRPV4 (P = 1.58×10−3). Among ever-smokers, SERPINA1 showed the most significant association with FEV1 (P = 8.41×10−5), followed by PDE4D (P = 1.22×10−4). The strongest association with FEV1/FVC ratio was observed with ABCC1 (P = 4.38×10−4), and ESR1 (P = 5.42×10−4) among ever-smokers. Conclusions Polymorphisms spanning previously associated lung function genes did not show strong evidence for association with lung function measures in the SpiroMeta consortium population. Common SERPINA1 polymorphisms may affect FEV1 among smokers in the general population.
IEEE Transactions on Biomedical Engineering | 2012
Muhammad Moazam Fraz; Paolo Remagnino; Andreas Hoppe; Bunyarit Uyyanonvara; Alicja R. Rudnicka; Christopher G. Owen; Sarah Barman
This paper presents a new supervised method for segmentation of blood vessels in retinal photographs. This method uses an ensemble system of bagged and boosted decision trees and utilizes a feature vector based on the orientation analysis of gradient vector field, morphological transformation, line strength measures, and Gabor filter responses. The feature vector encodes information to handle the healthy as well as the pathological retinal image. The method is evaluated on the publicly available DRIVE and STARE databases, frequently used for this purpose and also on a new public retinal vessel reference dataset CHASE_DB1 which is a subset of retinal images of multiethnic children from the Child Heart and Health Study in England (CHASE) dataset. The performance of the ensemble system is evaluated in detail and the incurred accuracy, speed, robustness, and simplicity make the algorithm a suitable tool for automated retinal image analysis.
British Journal of Ophthalmology | 2012
Christopher G. Owen; Zakariya Jarrar; Richard Wormald; Astrid E. Fletcher; Alicja R. Rudnicka
Background UK estimates of age related macular degeneration (AMD) occurrence vary. Aims To estimate prevalence, number and incidence of AMD by type in the UK population aged ≥50 years. Methods Age-specific prevalence rates of AMD obtained from a Bayesian meta-analysis of AMD prevalence were applied to UK 2007–2009 population data. Incidence was estimated from modelled age-specific prevalence. Results Overall prevalence of late AMD was 2.4% (95% credible interval (CrI) 1.7% to 3.3%), equivalent to 513 000 cases (95% CrI 363 000 to 699 000); estimated to increase to 679 000 cases by 2020. Prevalences were 4.8% aged ≥65 years, 12.2% aged ≥80 years. Geographical atrophy (GA) prevalence rates were 1.3% (95% CrI 0.9% to 1.9%), 2.6% (95% CrI 1.8% to 3.7%) and 6.7% (95% CrI 4.6% to 9.6%); neovascular AMD (NVAMD) 1.2% (95% CrI 0.9% to 1.7%), 2.5% (95% CrI 1.8% to 3.4%) and 6.3% (95% CrI 4.5% to 8.6%), respectively. The estimated number of prevalent cases of late AMD were 60% higher in women versus men (314 000 cases in women, 192 000 men). Annual incidence of late AMD, GA and NVAMD per 1000 women was 4.1 (95% CrI 2.4% to 6.8%), 2.4 (95% CrI 1.5% to 3.9%) and 2.3 (95% CrI 1.4% to 4.0%); in men 2.6 (95% CrI 1.5% to 4.4%), 1.7 (95% CrI 1.0% to 2.8%) and 1.4 (95% CrI 0.8% to 2.4%), respectively. 71 000 new cases of late AMD were estimated per year. Conclusions These estimates will guide health and social service provision for those with late AMD and enable estimation of the cost of introducing new treatments.
Computer Methods and Programs in Biomedicine | 2012
Muhammad Moazam Fraz; Sarah Barman; Paolo Remagnino; Andreas Hoppe; Abdul W. Basit; Bunyarit Uyyanonvara; Alicja R. Rudnicka; Christopher G. Owen
The change in morphology, diameter, branching pattern or tortuosity of retinal blood vessels is an important indicator of various clinical disorders of the eye and the body. This paper reports an automated method for segmentation of blood vessels in retinal images. A unique combination of techniques for vessel centerlines detection and morphological bit plane slicing is presented to extract the blood vessel tree from the retinal images. The centerlines are extracted by using the first order derivative of a Gaussian filter in four orientations and then evaluation of derivative signs and average derivative values is performed. Mathematical morphology has emerged as a proficient technique for quantifying the blood vessels in the retina. The shape and orientation map of blood vessels is obtained by applying a multidirectional morphological top-hat operator with a linear structuring element followed by bit plane slicing of the vessel enhanced grayscale image. The centerlines are combined with these maps to obtain the segmented vessel tree. The methodology is tested on three publicly available databases DRIVE, STARE and MESSIDOR. The results demonstrate that the performance of the proposed algorithm is comparable with state of the art techniques in terms of accuracy, sensitivity and specificity.
Ophthalmology | 2012
Alicja R. Rudnicka; Zakariya Jarrar; Richard Wormald; Derek G. Cook; Astrid E. Fletcher; Christopher G. Owen
OBJECTIVE To obtain prevalence estimates of age-related macular degeneration (AMD; late, geographic atrophy, neovascular) by age and gender amongst populations of European ancestry taking into account study design and time trends. DESIGN Systematic review of population-based studies published by September 2010 with quantitative estimates of geographic atrophy (GA), neovascular (NV), and late AMD prevalence. Studies were identified by a literature search of MEDLINE (from 1950), EMBASE (from 1980), and Web of Science (from 1980) databases. PARTICIPANTS Data from 25 published studies (57 173 subjects: 455 with GA, 464 with NVAMD, and 1571 with late AMD). METHODS Bayesian meta-regression of the log odds of AMD with age, gender, and year of study allowing for differences in study design characteristics, to estimate prevalences of AMD (late, GA, NVAMD) along with 95% credible intervals (CrI). MAIN OUTCOME MEASURES Log odds and prevalence of AMD. RESULTS There was considerable heterogeneity in prevalence rates between studies; for late AMD, 20% of the variability in prevalence rates was explained by differences in age and 50% by study characteristics. The prevalence of AMD increased exponentially with age (odds ratio [OR], 4.2 per decade; 95% CrI, 3.8-4.6), which did not differ by gender. There was some evidence to suggest higher risk of NVAMD in women compared with men (OR, 1.2; 95% CrI, 1.0-1.5). Compared with studies using fundus imaging and international classification systems, studies using fundus imaging with alternative classifications were more likely (OR, 2.7; 95% CrI, 1.1-2.8), and studies using alternative classifications without fundus imaging most likely to diagnose late AMD (OR, 2.9; 95% CrI, 1.3-7.8). There was no good evidence of trends in AMD prevalence over time. Estimated prevalence of late AMD is 1.4% (95% CrI, 1.0%-2.0%) at 70 years of age, rising to 5.6% (95% CrI, 3.9%-7.7%) at age 80 and 20% (95% CrI, 14%-27%) at age 90. CONCLUSIONS Studies using recognized classifications systems with fundus photography reported the lowest prevalences of AMD taking account of age and gender, and were stable over time, with a potentially higher risk of NVAMD for women. These prevalence estimates can be used to guide health service provision in populations of European ancestry.
International Journal of Obesity | 2009
Christopher G. Owen; Peter H. Whincup; Lia Orfei; Qurratul-Ain Chou; Alicja R. Rudnicka; Andrea K Wathern; Samantha J. Kaye; Johan G. Eriksson; Clive Osmond
Objective:Although obesity beginning early in life is becoming more common, its implications for coronary heart disease (CHD) risk in later life remain uncertain. We examined the relationship of body mass index (BMI) before 30 years of age to CHD risk in later life.Design:Systematic review of published studies relating BMI between age 2 and 30 years to later CHD risk. Studies were identified using Medline (1950 onwards), Embase (1980 onwards) and Web of Science (1970 onwards) databases (to November 2007).Measurements:Relative risks (RR) of CHD associated with a 1 standard deviation (s.d.) higher BMI (most based on a narrow age range at measurement) were extracted by two authors independently, and combined using random-effect models.Results:A total of 15 studies provided 17 estimates (731 337 participants, 23 894 CHD events) of the association of early BMI to later CHD outcome. BMI in early childhood (2–6 years, 3 estimates) showed a weak inverse association with CHD risk (RR 0.94, 95% CI 0.82–1.07). BMI in later childhood (7 to <18 years, 7 estimates) and BMI in early adult life (18–30 years, 7 estimates) were both positively related to later CHD risk (RR 1.09, 95% CI 1.00–1.20; RR 1.19, 95% CI 1.11–1.29 respectively). However, there was considerable statistical heterogeneity between study estimates. Results were unaffected by adjustment for social class and/or cigarette smoking, blood pressure and/or total cholesterol, in studies with available data. Gender and year of birth (1900–1976) had little effect on the association.Conclusions:BMI is positively related to CHD risk from childhood onwards; the associations in young adults are consistent with those observed in middle age. Long-term control of BMI from childhood may be important to reduce the risk of CHD.
Circulation | 2007
Alicja R. Rudnicka; Ann Rumley; Gordon Lowe; David P. Strachan
Background— Circulating levels of fibrinogen, fibrin D-dimer, C-reactive protein (CRP), tissue plasminogen activator antigen (t-PA) and von Willebrand factor are associated with incident coronary heart disease. We describe cross-sectional diurnal, seasonal, and blood-processing patterns for these variables, and assess whether they represent important sources of variability that should be taken into account in epidemiological studies or for additional risk prediction in individuals. Methods and Results— A total of 9377 men and women aged 45 years were visited in their homes and blood-sampled for fibrinogen, D-dimer, CRP, t-PA, and von Willebrand factor. These variables were examined in relation to the time of blood sample collection, day of the year, and delay in processing. All variables exhibited statistically significant diurnal sinusoidality (P≤0.02). Our models predicted a peak rise for fibrinogen and von Willebrand factor at midday, with overall diurnal variations of 3% and 10%, respectively, after adjustment for standard cardiovascular risk factors. D-dimer exhibited a peak at 14:00 hours, CRP at 15:00 hours, and t-PA at 10:00 hours with diurnal variations of 10%, 34%, and 55%, respectively, after full adjustment. All variables except CRP showed seasonal heterogeneity. Greater delays in processing blood samples were associated with higher levels of t-PA in particular. The proportion of variation attributed to the diurnal, seasonal, and processing effects was 2% for fibrinogen and von Willebrand factor; 9% for D-dimer, 1% for CRP, and 16% for t-PA. Conclusions— Temporal variations are important sources of heterogeneity that may bias the analysis of epidemiological studies and coronary heart disease risk prediction in individuals. Sample-processing delay is particularly important for t-PA.
PLOS Medicine | 2010
Peter H. Whincup; Claire M. Nightingale; Christopher G. Owen; Alicja R. Rudnicka; Ian Gibb; Catherine M. McKay; Angela S. Donin; Naveed Sattar; K. George M. M. Alberti; Derek G. Cook
Peter Whincup and colleagues carry out a cross-sectional study examining ethnic differences in precursors of of type 2 diabetes among children aged 9–10 living in three UK cities.