Statistical basis of clinical trials

Author(s):  
Jeremy Prout ◽  
Tanya Jones ◽  
Daniel Martin

This chapter summarizes some aspects of study design and statistical analysis to allow the anaesthetist to appraise research. Types of observational study are described and aspects of interventional studies such as sample size calculation and power are explained. Research governance, phases of drug trials and levels of evidence are described. A section on statistical analysis includes expression of proportion for binary data (odds ratio, number needed to treat) and use of probability and confidence intervals to measure statistical significance.

2019 ◽  
Vol 46 (2) ◽  
pp. 101-109 ◽  
Author(s):  
Spyridon N Papageorgiou ◽  
Georgios N Antonoglou ◽  
Conchita Martin ◽  
Theodore Eliades

Objective: The aim of this study was to explore the methods, reporting and transparency of clinical trials in orthodontics and compare them to the field of periodontics, as a standard within dentistry. Design/setting: Cross-sectional bibliographic study Methods: A total of 300 trials published in 2017–2018 and evenly distributed in orthodontics and periodontics were selected, assessed and analysed statistically to explore key aspects of the conduct and reporting of orthodontic clinical trials compared to trials in periodontics. Results: Several aspects are often neglected in orthodontic and periodontic trials and could be improved upon, including use of statistical expertise (22.3% of assessed trials), blinding of outcome assessors (62.3%), prospective trial registration (12.0%), adequate sample size calculation (35.7%), adherence to CONSORT (14.3%) and open data sharing (4.3%). The prevalence of statistically significant findings among orthodontic and periodontic trials was 62.3%, which was significantly associated with several methodological traits like statistician involvement (odds ratio [OR] = 0.5; 95% confidence interval [CI] = 0.3–0.9), blind outcome assessor (OR = 0.5; 95% CI = 0.2–1.0), lack of prospective trial registration (OR = 2.8; 95% CI = 1.3–5.9) and non-adherence to CONSORT (OR = 4.5; 95% CI = 1.3–15.8). Conclusions: Although trials in orthodontics seem to be significantly worse compared to periodontics in aspects like trial registration, adherence to CONSORT and declaration of competing interests or financial support, their methods do seem to have improved considerably in recent years.


Author(s):  
Philip Wiffen ◽  
Marc Mitchell ◽  
Melanie Snelling ◽  
Nicola Stoner

This chapter provides a brief overview to the concept of evidence-based medicine (EBM) starting with a well-accepted definition. The importance of clinical significance over statistical significance is discussed. A number of useful tools are presented and described to enable the practitioner to become competent in recognizing high-quality evidence and to have the skills to critically appraise evidence that is potentially important to their practice. There is a brief description of some of the statistical tools commonly used in EBM including binary data tools such as odds ratios, number needed to treat, and relative risks.


2002 ◽  
Vol 12 (4) ◽  
pp. 471-483 ◽  
Author(s):  
Hansheng Wang ◽  
Shein-Chung Chow ◽  
Gang Li

2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Bart Hiemstra ◽  
Frederik Keus ◽  
Jørn Wetterslev ◽  
Christian Gluud ◽  
Iwan C. C. van der Horst

Abstract Background All clinical research benefits from transparency and validity. Transparency and validity of studies may increase by prospective registration of protocols and by publication of statistical analysis plans (SAPs) before data have been accessed to discern data-driven analyses from pre-planned analyses. Main message Like clinical trials, recommendations for SAPs for observational studies increase the transparency and validity of findings. We appraised the applicability of recently developed guidelines for the content of SAPs for clinical trials to SAPs for observational studies. Of the 32 items recommended for a SAP for a clinical trial, 30 items (94%) were identically applicable to a SAP for our observational study. Power estimations and adjustments for multiplicity are equally important in observational studies and clinical trials as both types of studies usually address multiple hypotheses. Only two clinical trial items (6%) regarding issues of randomisation and definition of adherence to the intervention did not seem applicable to observational studies. We suggest to include one new item specifically applicable to observational studies to be addressed in a SAP, describing how adjustment for possible confounders will be handled in the analyses. Conclusion With only few amendments, the guidelines for SAP of a clinical trial can be applied to a SAP for an observational study. We suggest SAPs should be equally required for observational studies and clinical trials to increase their transparency and validity.


Author(s):  
Janislei Gislei Dorociaki Stocco ◽  
Hellen Hoers ◽  
Franciele Soares Pott ◽  
Karla Crozeta ◽  
Dulce Aparecida Barbosa ◽  
...  

Abstract Objective: to evaluate the effectiveness and safety in the use of second-generation central venous catheters impregnated in clorhexidine and silver sulfadiazine when compared with other catheters, being them impregnated or not, in order to prevent the bloodstream infection prevention. Method: systematic review with meta-analysis. Databases searched: MEDLINE, EMBASE, CINAHL, LILACS/SciELO, Cochrane CENTRAL; search in Congress Proceedings and records from Clinical Trials. Results: 1.235 studies were identified, 97 were pre-selected and 4 were included. In catheter-related bloodstream infection, there was no statistical significance between second-generation impregnated catheter compared with the non-impregnated ones, absolute relative risk 1,5% confidence interval 95% (3%-1%), relative risk 0,68 (confidence interval 95%, 0,40-1,15) and number needed to treat 66. In the sensitivity analysis, there was less bloodstream infection in impregnated catheters (relative risk 0,50, confidence interval 95%, 0,26-0,96). Lower colonization, absolute relative risk 9,6% (confidence interval 95%, 10% to 4%), relative risk 0,51 (confidence interval 95% from 0,38-0,85) and number needed to treat 5. Conclusion: the use of second-generation catheters was effective in reducing the catheter colonization and infection when a sensitivity analysis is performed. Future clinical trials are suggested to evaluate sepsis rates, mortality and adverse effects.


2021 ◽  
Vol 58 (2) ◽  
pp. 133-147
Author(s):  
Rownak Jahan Tamanna ◽  
M. Iftakhar Alam ◽  
Ahmed Hossain ◽  
Md Hasinur Rahaman Khan

Summary Sample size calculation is an integral part of any clinical trial design, and determining the optimal sample size for a study ensures adequate power to detect statistical significance. It is a critical step in designing a planned research protocol, since using too many participants in a study is expensive, exposing more subjects to the procedure. If a study is underpowered, it will be statistically inconclusive and may cause the whole protocol to fail. Amidst the attempt to maximize power and the underlying effort to minimize the budget, the optimization of both has become a significant issue in the determination of sample size for clinical trials in recent decades. Although it is hard to generalize a single method for sample size calculation, this study is an attempt to offer something that might be a basis for finding a permanent answer to the contradictions of sample size determination, by the use of simulation studies under simple random and cluster sampling schemes, with different sizes of power and type I error. The effective sample size is much higher when the design effect of the sampling method is smaller, particularly less than 1. Sample size increases for cluster sampling when the number of clusters increases.


2017 ◽  
Vol 157 (6) ◽  
pp. 921-927 ◽  
Author(s):  
Hyun Jin Min ◽  
Hyun Kang ◽  
Geun Joo Choi ◽  
Kyung Soo Kim

Objective Whether there is an association or a cause-and-effect relationship between epistaxis and hypertension is a subject of longstanding controversy. The objective of this systematic review and meta-analysis was to determine the association between epistaxis and hypertension and to verify whether hypertension is an independent risk factor of epistaxis. Data Sources A comprehensive search was performed using the MEDLINE, EMBASE, and Cochrane Library databases. Review Methods The review was performed according to the Meta-analysis of Observational Studies in Epidemiology guidelines and reported using the Preferred Reporting Items for Systematic Reviews and Meta-analysis guidelines. Results We screened 2768 unique studies and selected 10 for this meta-analysis. Overall, the risk of epistaxis was significantly increased for patients with hypertension (odds ratio, 1.532 [95% confidence interval (CI), 1.181-1.986]; number needed to treat, 14.9 [95% CI, 12.3-19.0]). Results of the Q test and I2 statistics suggested considerable heterogeneity ([Formula: see text] = 0.038, I2 = 49.3%). The sensitivity analysis was performed by excluding 1 study at a time, and it revealed no change in statistical significance. Conclusion Although this meta-analysis had some limitations, our study demonstrated that hypertension was significantly associated with the risk of epistaxis. However, since this association does not support a causal relationship between hypertension and epistaxis, further clinical trials with large patient populations will be required to determine the impact of hypertension on epistaxis.


2020 ◽  
Author(s):  
Lida Feyz ◽  
Yale Wang ◽  
Atul Pathak ◽  
Manish Saxena ◽  
Felix Mahfoud ◽  
...  

BACKGROUND Great and costly efforts are required to recruit potential participants into clinical trials. Using social media may make the recruitment process more efficient. Merely 20% of clinical trials are completed on time, a finding mostly linked to challenges in patient recruitment [1]. Recruitment through social media is increasingly being recognized as a tool to efficiently identify eligible subjects at lower costs [2, 3]. One of the key reasons for its success is the strong adherence of users to specific social media platforms. Facebook for instance has over 2.38 billion active monthly users of which about 75% access the network on a daily basis [4]. As such, the platform and other like it offer great potential to quickly and affordably enroll patients into clinical trials and surveys [3, 5-7]. At present, little evidence is available on the efficacy of using social media to recruit patients into cardiovascular and hypertension trials [8]. The aim of the present study was to evaluate the efficacy of social media as an approach to recruit hypertensive patients into the RADIANCE-HTN SOLO trial. OBJECTIVE The aim of the present study was to evaluate the efficacy of social media as an approach to recruit hypertensive patients into the RADIANCE-HTN SOLO trial. METHODS The RADIANCE-HTN SOLO (NCT02649426) is a multicenter, randomised study that was designed to demonstrate the efficacy and safety of endovascular ultrasound renal denervation (RDN) to reduce ambulatory blood pressure at 2 months in patients with combined systolic–diastolic hypertension in the absence of medications. Between March 28, 2016, and Dec 28, 2017, 803 patients were screened for eligibility and 146 were randomised to undergo RDN (n=74) or a sham procedure (n=72) [9]. Key entry criteria included: age 18-75 years with essential hypertension using 0-2 antihypertensive drugs. Patients were recruited from 21 hospitals in the USA and 18 hospitals in Europe. The study was approved by local ethics committees or institutional review boards and was performed in accordance with the declaration of Helsinki. All participants provided written informed consent. All recruitment materials including social media campaigns was approved by local ethics committees of the involved sites. Recruitment strategies included social media (Facebook), conventional advertisements (ads) (magazine, brochure/poster, radio, newspaper), web search (the clinical website, craigslist and web-browsing), and physician referral. Both newspaper ads and posters contained brief information about study entry criteria. Newspapers were distributed at public transport places and posters were displayed in outpatient cardiology and hypertension clinics. Radio ads were run for 30 or 60 seconds providing a short summary of the study, entry criteria and contact information. Ads were run in major metropolitan areas on radio stations with large adult listener bases during popular days and times. Facebook ads were targeted towards subjects >45 years old within a certain distance from a recruitment site (range 20-50 miles). Criteria were modified over time in order to increase response rates [i.e. distance was increased or decreased, age was increased to >55 year]. Facebook ads referred to a dedicated study website translated into country specific languages. If interested, subjects could complete an anonymous online screening questionnaire which provided direct automatic feedback on study eligibility. Eligible subjects were asked to provide contact details (name and telephone number) to receive additional information, a process coordinated via a secure online portal (Galen Gateway Patient Recruitment Portal, Galen Patient Recruitment, Inc., Cumberland, RI). Study site were only able to contact potential candidates within their area. The study sponsor was not able to access any personal data. Trained local site personnel or contracted secondary screeners contacted candidates by phone to verify eligibility and answer potential questions. A subsequent outpatient clinic visit was scheduled during which the study was explained in greater detail and the informed consent form could be signed. Statistical analysis Categorical variables were expressed as percentages and counts. Continuous variables were described as mean  standard deviation (SD) when normally distributed, data was compared using an Independent-Samples or Paired-Samples T test to analyze the difference between recruitment methods. In case of non-normal distribution, median data was presented with the interquartile range [IQR]. All statistical tests are 2-tailed. A P-value <0.05 was considered statistically significant. Statistical analysis was performed using SPSS statistical analysis (version 24.0).   RESULTS Results Facebook ads were active during a 115-day recruitment period between August and November 2017. A total of 285 potential candidates were recruited by different recruitment strategies in this specific time period, of which 184 (65%) were consented through Facebook (Table 1). The average age of the subjects consented through Facebook was 59 ± 8 years and 51% were male (Table 2). Facebook reached 5.3 million people in 168 separate campaigns run in proximity to 19 sites in the US and 14 sites in Europe. The number of candidates per site was variable with a median of 23 [17 – 26] candidates per site that passed the questionnaire (Figure 1). A total of 27/184 subjects were eventually randomised. Total cost for the Facebook ads was $152,412; costing $907/campaign and $0.83/click. This resulted in a total cost of $828/consent. During the same recruitment period, 7-day radio spots were launched with a total cost of $2,870; resulting in 9 inquiries with eventually 5 potential candidates and 2 consents ($1,435/consent).   CONCLUSIONS Conclusion Targeted social media was a successful and efficient strategy to find potential candidates for a multicenter blood pressure clinical trial. Whether this approach can be replicated across other disease states or demographics remains to be studied.


2021 ◽  
Vol 10 (7) ◽  
pp. 1487
Author(s):  
Isabel Añón-Oñate ◽  
Rafael Cáliz-Cáliz ◽  
Carmen Rosa-Garrido ◽  
María José Pérez-Galán ◽  
Susana Quirosa-Flores ◽  
...  

Rheumatic diseases (RD) and hereditary thrombophilias (HT) can be associated with high-risk pregnancies. This study describes obstetric outcomes after receiving medical care at a multidisciplinary consultation (MC) and compares adverse neonatal outcomes (ANOs) before and after medical care at an MC. This study is a retrospective observational study among pregnant women with RD and HT treated at an MC of a university hospital (southern Spain) from 2012 to 2018. Absolute risk reduction (ARR) and number needed to treat (NNT) were calculated. A total of 198 pregnancies were registered in 143 women (112 with RD, 31 with HT), with 191 (96.5%) pregnancies without ANOs and seven (3.5%) pregnancies with some ANOs (five miscarriages and two foetal deaths). Results previous to the MC showed 60.8% of women had more than one miscarriage, with 4.2% experiencing foetal death. MC reduced the ANO rate by AAR = 60.1% (95%CI: 51.6−68.7%). The NNT to avoid one miscarriage was 1.74 (95%CI: 1.5–2.1) and to avoid one foetal death NNT = 35.75 (95CI%: 15.2–90.9). A total of 84.8% of newborns and 93.2% of women did not experience any complication. As a conclusion, the follow-up of RD or HT pregnant women in the MC drastically reduced the risk of ANOs in this population with a previous high risk.


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