Imperial College London

MrMatyasSzigeti

Faculty of MedicineSchool of Public Health

Clinical Trials Unit Statistician
 
 
 
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16 results found

Elek LP, Szigeti M, Erdelyi-Hamza B, Smirnova D, Fountoulakis KN, Gonda Xet al., 2022, What you see is what you get? Association of belief in conspiracy theories and mental health during COVID-19., Neuropsychopharmacol Hung, Vol: 24, Pages: 42-55, ISSN: 1419-8711

Background: The COVID-19 pandemic brought about great uncertainty and significant changes in our people's everyday lives. In times of such crises, it is natural to seek explanations to overcome our fears and uncertainties, contributing to an increase to believe in conspiracy theories which, by yielding explanations, decrease uncertainty and ambiguity and may thus have an effect on mental well-being. In spite of this, the majority of research on conspiracy theories focused on their social effects with little attention to psychological effects. Thus, the aim of our present study was to examine the association between belief in conspiracy theories and different aspects of mental health during the COVID-19 pandemic in a general population sample. Methods: Our analyses included data from the Hungarian leg of the COMET-G (COVID-19 MEntal health international for the General population) study. The Hungarian sample included participants who completed a detailed questionnaire assessing belief in seven conspiracy theory items, as well as STAI-S and CES-D to measure state anxiety and depression, respectively, and answered questions related to their change in depression, anxiety and suicidal thoughts during the pandemic. Association between the individual beliefs as well as a composite Conspiracy Theory Belief Score (CTBS) and mental health measures was analysed using linear regression models. Results: Overall, belief in conspiracy theories was relatively moderate in our sample. Sex and age appeared to have a significant effect on the Overall Conspiracy Theory Belief Score (CTBS), with women having a higher score and scores increasing with age. Some of the individual beliefs also showed associations with age and sex. State anxiety and depression was not significantly associated with CTBS, however in case of depression some individual items were, and symptom clusters within CES-D also showed a pattern of association with some of the individual items. As far as changes in mental

Journal article

Ferenci T, Szigeti M, Kovacs L, 2022, Using non-stationary extreme value analysis to characterize blood glucose curves, Pages: 171-176

Introduction: The application of extreme value statistics provides a novel way to characterize the risk of high blood glucose levels. Its statistical methodology works well for dependent data, but the impact of non-stationarity is unclear.Material and Methods: 14.7 million blood glucose measurements from 225 patients were analyzed with stationary and nonstationary extreme value models. In case of the latter, the location parameter was allowed to vary with time using spline expansion to allow for a flexible, data-driven functional form.Results: Estimated scale and shape parameters were almost identical (correlation > 0.99) and estimated location was also similar (correlation =0.9). One-year return level and estimated time spent in a year above the clinically relevant threshold of 600 mg/dl was also very similar, and estimated time spent above 400 mg/dl was similar with the exception of a single patient, who had much higher value with the stationary model.Discussion and Conclusion: Non-stationary extreme values models can be applied to analyze blood glucose measurements with the aim of measuring the risk of hyperglycaemia. Obtained results are similar to those with stationary models, but whether it is possible (and if so, to what extent) that the estimated longterm trend in location picks up some effect of true extremity requires further investigation.

Conference paper

Szigeti M, Ferenci T, Kovács L, 2021, The Use of Extreme Value Statistics to Characterize Blood Glucose Curves and Patient Level Risk Assessment of Patients With Type I Diabetes., J Diabetes Sci Technol

OBJECTIVE: Characterizing blood glucose curves and providing precise patient level risk assessment of hyperglycemia using extreme value statistics and comparing these assessments with traditional indicators of glycemic variability which are not designed to specifically capture the risk of hyperglycemia. RESEARCH DESIGN AND METHODS: One year return level (blood glucose level exceeded exactly once every year on average) and probability of exceeding and expected time spent above certain thresholds (600 and 400 mg/dL) per year were calculated. As a comparison, traditional metrics for glycemic variability were determined too. The effect of body mass index on extremes was also investigated using non-stationary models. Metrics were calculated on a dataset containing 170.8 patient-years of measurements of 226 patients. RESULTS: Nine high-risk patients were identified with the novel metrics: their estimated time spent above 600 mg/dL per year were above 2 hours. These patients were at moderate risk according to the traditional metrics. Higher body mass index was associated with more extreme glucose levels. CONCLUSIONS: Through these estimates it is possible to assess each patient's individual clinical risk of hyperglycemia even beyond the observed blood glucose levels and detection limits. Additionally, it allows the assessment of the impact of clinical characteristics and treatments on blood glucose control in a novel, mathematically well-founded and potentially clinically more useful way than the already existing indicators.

Journal article

Tan P-T, Cro S, Van Vogt E, Szigeti M, Cornelius Vet al., 2021, A review of the use of controlled multiple imputation in randomised controlled trials with missing outcome data, BMC Medical Research Methodology, Vol: 21, ISSN: 1471-2288

Background:Missing data are common in randomised controlled trials (RCTs) and can bias results if not handled appropriately. A statistically valid analysis under the primary missing-data assumptions should be conducted, followed by sensitivity analysis under alternative justified assumptions to assess the robustness of results. Controlled Multiple Imputation (MI) procedures, including delta-based and reference-based approaches, have been developed for analysis under missing-not-at-random assumptions. However, it is unclear how often these methods are used, how they are reported, and what their impact is on trial results. This review evaluates the current use and reporting of MI and controlled MI in RCTs.Methods:A targeted review of phase II-IV RCTs (non-cluster randomised) published in two leading general medical journals (The Lancet and New England Journal of Medicine) between January 2014 and December 2019 using MI. Data was extracted on imputation methods, analysis status, and reporting of results. Results of primary and sensitivity analyses for trials using controlled MI analyses were compared.Results:A total of 118 RCTs (9% of published RCTs) used some form of MI. MI under missing-at-random was used in 110 trials; this was for primary analysis in 43/118 (36%), and in sensitivity analysis for 70/118 (59%) (3 used in both). Sixteen studies performed controlled MI (1.3% of published RCTs), either with a delta-based (n = 9) or reference-based approach (n = 7). Controlled MI was mostly used in sensitivity analysis (n = 14/16). Two trials used controlled MI for primary analysis, including one reporting no sensitivity analysis whilst the other reported similar results without imputation. Of the 14 trials using controlled MI in sensitivity analysis, 12 yielded comparable results to the primary analysis whereas 2 demonstrated contradicting results. Only 5/110 (5%) trials using missing-at-random MI and 5/16 (31%) trials using con

Journal article

Gohel M, Mora J, Szigeti M, Epstein D, Heatley F, Bradbury A, Bulbulia R, Cullum N, Nyameke I, Poskitt K, Renton S, Warwick J, Davies Aet al., 2020, Long-term clinical and cost-effectiveness of early endovenous ablation in venous ulceration (The EVRA randomized clinical trial), JAMA: Journal of the American Medical Association, ISSN: 0098-7484

ImportanceOne-year outcomes from the Early Venous Reflux Ablation (EVRA) randomized trial showed accelerated venous leg ulcer healing and greater ulcer free time for participants treated with early endovenous ablation of lower extremity superficial reflux. Outcomes up to 5 years are presented here.ObjectiveTo evaluate the clinical and cost-effectiveness of early endovenous ablation of superficial venous reflux in patients with venous leg ulceration.DesignRandomized clinical trial.SettingVascular surgery departments in twenty United Kingdom hospitalsParticipantsBetween October 2013 and September 2016, 450 participants (450 legs) with venous leg ulceration of <6 months and superficial venous reflux were enrolled. InterventionsPatients were randomly assigned to receive compression therapy with early endovenous ablation within 2 weeks of randomization (early intervention, n=224) or compression with deferred endovenous treatment of superficial venous reflux (deferred intervention, n=226). Endovenous modality and strategy were left to the preference of the treating clinical team. Main outcomes and measuresThe primary outcome for the extended phase was time to first ulcer recurrence. Secondary outcomes included ulcer recurrence rate and cost effectiveness.ResultsOf 426 participants whose leg ulcer had healed, 121 (28.4%) experienced at least one recurrence during follow-up. There was no clear difference in time to first ulcer recurrence between the two groups (hazard ratio 0.82; 95% confidence interval [CI] 0.57 to 1.17; P=0.278). Ulcers recurred at a lower rate of 0.107 per person year (PY) in the early-intervention group compared to 0.162 per PY in the deferred-intervention group (incidence rate ratio 0.658; 95% CI: 0.480 to 0.898, p=0.003). Time to ulcer healing was shorter in the early-intervention group for primary ulcers (hazard ratio 1.36; 95% CI 1.12 to 1.64, p=0.002). At three years, early intervention is 91.6% likely to be cost-effective at a willingness to pa

Journal article

Szigeti M, Ferenci T, Kovacs L, 2020, The use of block maxima method of extreme value statistics to characterise blood glucose curves, Pages: 433-437

In contrast to regular statistics where the focus is on the most typical part of the data and the used metrics are describing that part (usually with the mean or median and variance and interquartile range) where most of the observations came from, there is a branch of statistics which focuses on the extreme events, i.e, the tails of the distributions. These are not simple outliers, like data entry errors, but real part of the data which are far from the central tendency and occur rarely, yet, have relevance and impact. Thus, in many application, they can't be simply neglected. The use of extreme value statistics allows us to fit models on this part of the data and like 'regular' statistics, enables us to calculate estimates and predictions, but in this case for extreme values. These methods are frequently used in fields like meteorology and finance where the extreme events have large impact despite their rarity. Because of this rarity, however, only a small fraction of the data can be used so much higher sample size is required for such analysis. This factor limited the use of extreme value statistics in biomedical field where available technology and costs are strong limitations at frequently measuring most of the biomarkers until recently. Blood glucose level is one of the exceptions nowadays, as with recent advancements it can be monitored for relatively long time and with high frequency for a patient. Additionally, extreme values of blood glucose levels (both high and low) are associated with- chronic or acute- complications of diabetes. This paper aims to demonstrate that the use of extreme value statistics, in particular the block maxima approach could be a possible way to characterize blood glucose curves. In addition to providing a metric for the state of the patient and therefore hopefully the associated risks, it allows the comparison of the performance of artificial pancreas systems. Block maxima method was used to model extreme values of a dataset conta

Conference paper

Szigeti M, Ferenci T, Kovacs L, 2020, The use of peak over threshold methods to characterise blood glucose curves, Pages: 199-204

In contrast to regular statistics which focuses on the typical part of the data and use metrics to describe that part (usually the mean or variance), there is a branch of statistics which focuses on the extreme and thus rare events. The use of extreme value statistics allows us to fit models on this part of the data and like regular statistics, enables us to calculate estimates and predictions, but in this case for extreme values. These methods are frequently used in fields like meteorology and finance where the extreme events has large impact despite their rarity. Because of this rarity, however, only a small fraction of the data can be used so much higher sample size is required for such analysis - thus fields with a large amount of historical data have an advantage.This factor limited the use of extreme value statistics in biomedical field where available technology and costs are strong limitations at measuring most of the biomarkers until recently.Blood glucose level is one of the exceptions nowadays, as with recent advancements it can be monitored for relatively long time and with high frequency for a patient. Additionally, extreme values of blood glucose levels (both high and low) are associated with - chronic or acute - complications of diabetes.This paper aims to demonstrate that the use of extreme value statistics could be a possible way to characterize blood glucose curves. In addition to providing a metric for the state of the patient, it allows the comparison of the performance of artificial pancreas models.Peak over threshold method was used to model extreme values of a simulated dataset containing 1440 measurements of 99 patients with 250 mg/dl as threshold. Probabilities for exceeding the clinically relevant levels of 270 mg/dl (cognitive symptoms expected) and 600 mg/dl (diabetic hyperosmolar syndrome) were calculated and were 23.9% and 8.0 • 10-6% respectively in the region above the threshold (250 mg/dl). Through these estimates it is possible

Conference paper

Szigeti M, Kovács L, Ferenci T, 2019, Stability of relative and absolute metrics: Empirical evidence from pulmonology, Pages: 235-238

It has been widely argued that absolute treatment effect measurements (such as risk difference) reveal the "clinical benefit" of an intervention. Yet, many previous experience with binary endpoints have shown that they are unlikely to be transportable between populations. As absolute metrics are usually derived from baseline risk and relative metric (such as odds ratio), it seems logical to rather measure relative metrics, assuming they are stable. In the present study, a continuous endpoint was used to assess the stability of both relative and absolute metrics using a empirical data from pulmonology. Results are preliminary due to the low baseline variability, yet, the difference was significantly correlated with the baseline, unlike the ratio, which is in line with previous experience with binary endpoints. Further research is needed to explore the stability with continuous endpoints.

Conference paper

Poulter NR, Savopoulos C, Anjum A, Apostolopoulou M, Chapman N, Cross M, Falaschetti E, Fotiadis S, James RM, Kanellos I, Szigeti M, Thom S, Sever P, Thompson D, Hatzitolios AIet al., 2018, Randomized crossover trial of the impact of morning or evening dosing of antihypertensive agents on 24-hour ambulatory blood pressure: the HARMONY trial, Hypertension, Vol: 72, Pages: 870-873, ISSN: 0194-911X

Some data suggest that nocturnal dosing of antihypertensive agents may reduce cardiovascular outcomes more than daytime dosing. This trial was designed to evaluate whether ambulatory blood pressure monitoring levels differ by timing of drug dosing. Patients aged 18 to 80 years with reasonably controlled hypertension (≤150/≤90 mm Hg) on stable therapy of ≥1 antihypertensive agent were recruited from 2 centers in London and Thessaloniki. Patients were randomized to receive usual therapy either in the morning (6 am–11 am) or evening (6 pm–11 pm) for 12 weeks when participants crossed over to the alternative timing for a further 12 weeks. Clinic blood pressures and a 24-hour recording were taken at baseline, 12, and 24 weeks and routine blood tests were taken at baseline. The study had 80% power to detect 3 mm Hg difference in mean 24-hour systolic blood pressure (α=0.05) by time of dosing. A 2-level hierarchical regression model adjusted for center, period, and sequence was used. Of 103 recruited patients (mean age, 62; 44% female), 95 patients (92%) completed all three 24-hour recordings. Mean 24-hour systolic and diastolic blood pressures did not differ between daytime and evening dosing. Similarly, morning and evening dosing had no differential impact on mean daytime (7 am–10 pm) and nighttime (10 pm–7 am) blood pressure levels nor on clinic levels. Stratification by age (≤65/≥65 years) or sex did not affect results. In summary, among hypertensive patients with reasonably well-controlled blood pressure, the timing of antihypertensive drug administration (morning or evening) did not affect mean 24-hour or clinic blood pressure levels.

Journal article

Johnston SL, Szigeti M, Cross M, 2018, Correction: Azithromycin for acute exacerbations of Asthma: The AZALEA randomized clinical trial (JAMA Internal Medicine (2016) 176:11 (1630-1637) DOI: 10.1001/jamainternmed.2016.5664), JAMA Internal Medicine, Vol: 178, Pages: 1003-1003, ISSN: 2168-6106

© 2018 American Medical Association. All rights reserved. IncorrectNumbersofAdverseEventsReported: The Original Investigation titled "Azithromycin for Acute Exacerbations of Asthma: The AZALEAR and omized Clinical Trial,"1published in the November 2016 issue of JAMA Internal Medicine, reported incorrect numbers of adverse events owing to a recently discovered error in the AZALEA clinical trial database. In the last paragraph of the Results section, "a reduced frequency of respiratory, thoracic, and mediastinal (63 of 64 respiratory) adverse events (27 vs 37, respectively)" should read "a reduced frequency of respiratory, thoracic, and mediastinal (61 of 62 respiratory) adverse events (26 vs 36, respectively)." Inthe online-only Supplement, numbers of adverse events were reported incorrectly in eTables 16 through 19. This article and its supplement have been corrected online.

Journal article

Johnston SL, Szigeti M, Cross M, Brightling C, Chaudhuri R, Harrison T, Mansur A, Robison L, Sattar Z, Jackson D, Mallia P, Wong E, Corrigan C, Higgins B, Ind P, Singh D, Thomson NC, Ashby D, Chauhan Aet al., 2016, Azithromycin for acute exacerbations of asthma. The AZALEA randomized clinical trial, JAMA Internal Medicine, Vol: 176, Pages: 1630-1637, ISSN: 2168-6106

Importance Guidelines recommend against antibiotic use to treat asthma attacks. A study with telithromycin reported benefit, but adverse reactions limit its use.Objective To determine whether azithromycin added to standard care for asthma attacks in adults results in clinical benefit.Design, Setting, and Participants The Azithromycin Against Placebo in Exacerbations of Asthma (AZALEA) randomized, double-blind, placebo-controlled clinical trial, a United Kingdom–based multicenter study in adults requesting emergency care for acute asthma exacerbations, ran from September 2011 to April 2014. Adults with a history of asthma for more than 6 months were recruited within 48 hours of presentation to medical care with an acute deterioration in asthma control requiring a course of oral and/or systemic corticosteroids.Interventions Azithromycin 500 mg daily or matched placebo for 3 days.Main Outcomes and Measures The primary outcome was diary card symptom score 10 days after randomization, with a hypothesized treatment effect size of −0.3. Secondary outcomes were diary card symptom score, quality-of-life questionnaires, and lung function changes, all between exacerbation and day 10, and time to a 50% reduction in symptom score.Results Of 4582 patients screened at 31 centers, 199 of a planned 380 were randomized within 48 hours of presentation. The major reason for nonrecruitment was receipt of antibiotics (2044 [44.6%] screened patients). Median time from presentation to drug administration was 22 hours (interquartile range, 14-28 hours). Exacerbation characteristics were well balanced across treatment arms and centers. The primary outcome asthma symptom scores were mean (SD), 4.14 (1.38) at exacerbation and 2.09 (1.71) at 10 days for the azithromycin group and 4.18 (1.48) and 2.20 (1.51) for the placebo group, respectively. Using multilevel modeling, there was no significant difference in symptom scores between azithromycin and placebo at day 10 (difference

Journal article

Johnston SL, Szigeti M, Cross M, Brightling CE, Chaudhuri R, Harrison T, Mansur AH, Robinson L, Sattar Z, Jackson DJ, Mallia P, Wong EHC, Corrigan C, Higgins B, Ind P, Singh D, Thomson NC, Ashby D, Chauhan Aet al., 2016, A Randomised, Double-Blind, Placebo-Controlled Study To Evaluate The Efficacy Of Oral Azithromycin (500 Mg Od) As A Supplement To Standard Care For Adult Patients With Acute Exacerbations Of Asthma (the Azalea Trial), Publisher: AMER THORACIC SOC

Conference paper

Poulter N, Anjum A, Cross M, Falaschetti E, Savopoulos C, Szigeti M, Thom S, Hatzitolios Aet al., 2016, A comparison of the impact of morning or night delivery of antihypertensive agents on 24 hour ambulatory blood pressure monitoring (ABPM) levels: a randomised cross-over trial, Pages: 641-641

Conference paper

Poulter N, Anjum A, Cross M, Falaschetti E, Savopoulos C, Kanellos I, Szigeti M, Thom S, Hatzitolios Aet al., 2016, LBOS 01-01A COMPARISON OF THE IMPACT OF MORNING OR NIGHT DELIVERY OF ANTIHYPERTENSIVE AGENTS ON 24 HOUR ABPM LEVELS: A RANDOMISED CROSS-OVER TRIAL (HARMONY).

Conference paper

Abbara A, Jayasena CN, Christopoulos G, Narayanaswamy SN, Izzi-Engbeaya C, Nijher G, Comninos A, Peters D, Buckley A, Ratnasabapathy R, Prague JK, Salim R, Lavery SA, Bloom SR, Szigeti M, Ashby D, Trew G, Dhillo WSet al., 2015, Efficacy of kisspeptin-54 to trigger oocyte maturation in women at high risk of OHSS during IVF therapy, Journal of Clinical Endocrinology and Metabolism, Vol: 100, Pages: 3322-3331, ISSN: 0368-1610

Context:In Vitro Fertilization (IVF) treatment is an effective therapy for infertility, but can result in the potentially life-threatening complication ‘ovarian hyperstimulation syndrome’ (OHSS).Objective:To investigate whether kisspeptin-54 can be used to effectively and safely trigger oocyte maturation in women undergoing IVF treatment at high risk of developing OHSS.Design:Phase 2 multi-dose open label randomized clinical trial carried out during 2013–2014.Setting:Hammersmith Hospital IVF unit, London, UK.Patients:Sixty women at high risk of developing OHSS Intervention:Following a standard recombinant FSH/GnRH antagonist protocol, patients were randomized to receive a single injection of kisspeptin-54 to trigger oocyte maturation using an adaptive design for dose allocation (3.2nmol/kg, n=5; 6.4nmol/kg, n=20; 9.6nmol/kg, n=15; 12.8nmol/kg, n=20). Oocytes were retrieved 36hrs after kisspeptin-54 administration, assessed for maturation, and fertilized by intra-cytoplasmic sperm injection (ICSI) with subsequent transfer of one or two embryos. Women were routinely screened for the development of OHSS.Main Outcome Measure:Oocyte maturation was measured by oocyte yield (percentage of mature oocytes retrieved from follicles ≥14mm on ultrasound). Secondary outcomes include rates of OHSS and pregancy. Results:Oocyte maturation occurred in 95% of women. Highest oocyte yield (121%) was observed following 12.8nmol/kg kisspeptin-54, which was +69% (CI -16%,+153%) greater than following 3.2nmol/kg. At all doses of kisspeptin-54, biochemical pregnancy, clinical pregnancy and live birth rates per transfer (n=51) were 63%, 53% and 45%, respectively. Highest pregnancy rates were observed following 9.6nmol/kg kisspeptin-54 (85%, 77% and 62%, respectively). No woman developed moderate, severe or critical OHSS.Conclusion:Kisspeptin-54 is a promising approach to effectively and safely trigger oocyte

Journal article

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