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Conventional trial designs are resource and time-intensive. To accelerate the process of testing new interventions, we now have several novel research trial designs. This article focuses on master protocol trials, which allow several therapies to be tested within a single larger trial.

Previous articles in this series have looked at various aspects of planning, designing, conducting and interpreting biomedical research. In this article, we offer an overview of some tools and resources available to health and biomedical researchers, to help them with their research.

Calculation of sample size is an essential part of research study design since it affects the reliability and feasibility of the research study. In this article, we look at the principles of sample size calculation for different types of research studies.

Background and Aims: Acute kidney injury (AKI) is a significant postoperative complication. Multiple perioperative factors are implicated in the causation of AKI in the postoperative period in patients with oesophageal cancer. The study aimed to find out the incidence, causes and effects of AKI following oesophagectomy surgery. Methods: A prospective observational study was conducted in consecutive adult patients undergoing elective oesophagectomy at a tertiary cancer care hospital. Patients with preoperative chronic renal insufficiency (serum creatinine >1.5 mg/dl), AKI in the past and a history of renal replacement therapy were excluded. Serum creatinine values were measured on postoperative days 1, 3, 5, the day of discharge or day 15 and on the day of first follow-up or day 28, following oesophagectomy surgery. The incidence of AKI was measured using the ‘Kidney Disease Improving Global Outcome’ (KDIGO) criteria. Results: The incidence of AKI was 14.7% [95% confidence interval (CI) 9.9%, 20.7%] (i.e., 27/183) in patients who underwent elective oesophagectomy. AKI was associated with prolonged hospital stay [median- 13 days (interquartile range {IQR} 11–21.5) versus 9 days (IQR 8–12), P < 0.001] and increased in-hospital mortality (14.8% versus 1.3%, P 0.004, odds ratio = 13.2, 95% CI 2.3, 77.3). After multivariate analysis, age, anastomotic leak and use of vasopressors in the postoperative period were independent predictors of AKI. Conclusion: The incidence of AKI was 14.7% after elective oesophagectomy. AKI was associated with prolonged hospital stay and in-hospital mortality. Higher age, anastomotic leak and use of vasopressors in the postoperative period were independent predictors of AKI.

Missing data are an inevitable part of research and lead to a decrease in the size of the analyzable population, and biased and imprecise estimates. In this article, we discuss the types of missing data, methods to handle missing data and suggest ways in which missing data can be minimized.

Validity and reliability refer to the accuracy and consistency of a research tool. In the previous article in this series, we examined the development of a research questionnaire. In this article, we discuss the methods of determining the validity and reliability of a research questionnaire.

Simulation-based training (SBT) aims to acquire technical and non-technical skills in a simulated fashion without harming the patient. Simulation helps the anaesthesiologist acquire procedural competence and non-technical abilities. In thoracic anaesthesia, various simulators are available with varying degrees of fidelity and costs. Apart from improving bronchoscopy-related skills, other potential applications of SBT include the practice of lung isolation in normal and difficult airway scenarios, troubleshooting complications during surgeries, and certification of the proficiency of anaesthesiologists. A pragmatic approach is required for choosing the simulator based on its availability, cost, and benefits. Although the literature supports SBT to improve procedural skills, retention of the skills and their translation into improving clinical outcomes remain largely unproven. Randomised, controlled studies targeting the effect of SBT on the improvement of clinical outcomes of patients are needed to prove their worth.

Background and Aims: During proximal or distal migration of lung isolation device (LID), the bronchial cuff would move into a wider or narrower portion of the bronchus, leading to a decrease or increase in the cuff pressure, respectively. To test this hypothesis, we conducted a study to find out the efficacy of continuous bronchial cuff pressure (BCP) monitoring for detecting the displacement of LID. Methods: A single-arm interventional study was conducted including hundred adult patients undergoing elective thoracic surgeries using a left-sided LID. BCP was monitored in a continuous manner using a pressure transducer connected to the bronchial cuff of the LID. The position of the LID was assessed using a paediatric bronchoscope. Changes in the BCP were noted when the LID was moved intentionally in the left main bronchus (part 1) and during the surgery (part 2). Bronchoscopic confirmation was performed at the end of the surgery to note any uncaptured movement of the LID (part 3). Results: During part 1 of the study, BCP consistently decreased on the proximal movement and increased on the distal movement of the LID, although the magnitude of change was not constant. During part 2 of the study, sensitivity, specificity, positive predictive value, negative predictive value and accuracy of continuous BCP monitoring to detect the dislodgement of LIDs (n = 41) during the surgery were 97.6%, 40%, 76.9%, 88.9% and 78.7%, respectively. Conclusion: Continuous BCP monitoring is a useful and sensitive method for monitoring the position of left-sided LIDs in limited-resource settings.

Cannabis is one of the world's oldest cultivated plants and the most commonly used recreational drug worldwide. The plant relevant for medicinal use is Cannabis sativa that has two pharmacologically active ingredients – delta-9-tetrahydrocannabinol that is psychoactive and cannabidiol that does not have psychotropic activity. The policy tapestry of Cannabis has undergone a significant change in the past few decades worldwide. Different countries have diverse policies, ranging from classifying use of Cannabis as illicit, to legalization of its use, both for medicinal and recreational purposes. Cannabis products are approved for use, for instance, in multiple sclerosis and Dravet syndrome (US Food Drug and Administration). Against this backdrop, we find that the knowledge foundations for use of Cannabis in clinical trials in India are still evolving. Conducting ethical research within a clinical trials framework is essential to understand dosing, formulation, shelf life, drug–drug interaction, tolerability, and safety before establishing its utility for various indications. In the absence of guidelines or a regulatory framework for conduct of these studies, the various Institutional Ethics Committees (IECs), which are responsible for reviewing projects related to Cannabis, face unique challenges with respect to the basic requirements. The principal investigators (PIs) are equally strained to find local guidance, recommendations, and literature in support of their application to the respective IEC, thus leading to an impasse and delay in initiating the proposed clinical studies with Cannabis. The present article addresses considerations, questions, and issues that affect the conduct of these clinical studies and recommends mandatory documents and some suggested guidelines for use by both PIs and IECs to take studies with Cannabis forward until such time that an interdisciplinary regulatory framework is firmed up by regulatory authority.

Questionnaires are often used as part of research studies to collect data from participants. However, the information obtained through a questionnaire is dependent on how it has been designed, used, and validated. In this article, we look at the types of research questionnaires, their applications and limitations, and how a new questionnaire is developed.

Background and Aims: Translaryngeal ultrasonography (TLUSG) for diagnosis of vocal cord palsy, a relatively new, safe and noninvasive bedside technique with minimal risk of respiratory infection transmission, has been effective in patients with thyroid disease. We studied its use as an alternative method to visual inspection by flexible laryngoscopy (FL) for vocal cord assessment in patients undergoing thoracic surgeries. Methods: After Institutional Ethics Committee approval and trial registration, in this single-arm, prospective study, the vocal cord function of 110 patients who underwent either total oesophagectomy or mediastinoscopy was assessed immediately after extubation by both FL and TLUSG. A follow-up assessment was done by laryngoscopy using Hopkin's endoscope (HL) and a repeat TLUSG. The primary outcome was the concordance between direct visualisation (FL or HL) and TLUSG. Results: Vocal cords were successfully visualised by TLUSG in 90% of male and all female patients. Findings of FL and TLUSG done at the first assessment matched in 89 (86.4%) out of 103 patients, and the degree of concordance was 0.69 (95% confidence interval [CI] =0.52–0.83). At the second assessment, HL and TLUSG findings matched in 83 (94.3%) out of 88 patients, and the degree of concordance was 0.89 (95% CI = 0.77–0.98). Conclusion: TLUSG is an effective noninvasive alternative to direct visualisation for vocal cord assessment in both male and female patients undergoing thoracic surgery.

Virtual clinical trials refer to clinical trials that take advantage of digital technologies, including computer and mobile device apps, web-based tools, and remote monitoring devices, for one or more of the trial processes, such as participant recruitment, counseling, informed consent, measurement of endpoints, and/or adverse event monitoring, to obviate or reduce the need for participant visits to the trial site. The advantages of such trials may include higher recruitment rates, better compliance, lower dropout rates, reduction in time for trial completion, and lower costs. The use of such trials increased manifold during the COVID-19 pandemic and is likely to continue in the future.

Studies sometimes aim to show that a new intervention is not substantially worse than the existing standard of care while offering some benefits, for example, lower cost, decreased toxicity, or easier administration. Such studies are called non-inferiority (NI) trials. In this article, we look at some aspects of NI trials.

Background and Aims: Bedside ultrasound (US) is used to evaluate gastric residual volume (GRV) and assess aspiration risk. We examined the accuracy of US-guided measurement of GRV using Perlas's formula, by two trained anaesthesiologists, in patients who had consumed different types and volumes of fluids. Methods: Patients with no risk factors for delayed gastric emptying were included. Each assessor independently determined the baseline US-guided GRV. The patients were randomly allocated to receive no drink or 100 or 200 mL of water or milk. US-guided GRV was re-assessed within 5 min after the intervention. Investigators were blinded to the measurements performed by each other and to the randomisation arm. The primary outcome was the agreement between actual volumes consumed and estimated change in GRV. Results: Agreement between actual volume consumed and estimated change in GRV was poor [Intra-class correlation coefficient (ICC) 0.46, 95% confidence interval (CI) 0.09 to 0.72; P = 0.09 for assessor 1 and ICC 0.37; 95% CI 0.02 to 0.66; P = 0.03 for assessor 2]. Conclusion: US-guided GRV measurements using Perlas's formula, performed by trained anaesthesiologists may not be a reliable measure of GRV.

In an equivalence trial, researchers aim to show that a new intervention is more or less similar to an existing standard of care, i.e., the two are “equivalent”. In this article, we discuss some aspects of the design, analysis, interpretation and reporting of equivalence trials.

Screening tests are done to diagnose asymptomatic disease in apparently healthy people with the aim to reduce mortality and morbidity from the disease. Certain criteria need to be fulfilled before we adopt population-level screening for any disease. Several biases exist in evaluating screening studies, and the ideal study design would be a randomized trial with hard endpoints such as mortality and morbidity.

Background and Aims: The application of cricoid pressure (CP) for rapid sequence induction is questioned on two grounds: its effectiveness in clinical settings and its impact on the laryngeal view. The main reason cited for its ineffectiveness is the lack of knowledge and training in its correct application. This study assessed, the performance of anesthetists in applying effective CP in a clinical setting. Material and Methods: Eighty-five ASA I/II adult patients posted for elective surgery requiring oral endotracheal intubation with nasogastric tube (NGT) placement participated in the study. Eighty-five anesthetists divided into five groups based on their level of experience were randomly chosen to apply CP after induction of anesthesia. An experienced anesthetist performed videolaryngoscopy and attempted NGT insertion. The primary outcome was effectiveness of CP defined as the inability to pass the NGT into the esophageal opening. We also noted that the glottic view with and without CP and the effectiveness of CP across different levels of experience of anesthetists. Results: Of the 85 anesthetists, 61 (71.8%) applied effective CP. The effectiveness improved with experience (first-year residents-11/17 [64.7%], second-year residents-11/17 [64.7%], third-year residents-10/17 [58.8%], senior residents-13/17 [76.5%], and consultants-16/17 [94.1%]) (P = 0.157). Post hoc analysis showed higher effectiveness among anesthetists with >3 years of experience (85.3%) compared with

PURPOSEThe 2018 WHO health workforce report analyzing gender equity in 104 countries reported that although women constituted 70% of the workers, they were less likely to be employed full-time and faced a 28% gender pay gap. The ongoing COVID-19 pandemic has affected professional as well as personal lives of physicians. We conducted a survey among Indian physicians to understand this impact.METHODSA 31-point anonymized survey to evaluate the impact of the COVID-19 pandemic and resultant lockdown on physicians' domestic responsibilities was disseminated via e-mail and text messaging applications. Our aim was to evaluate whether the impact was gender-based and to look for differences in aspects of domestic work, childcare, and professional commitments.RESULTSWe obtained 1,041 responses, of which 643 identified themselves as men and 393 as women. An increase in the domestic responsibilities during the lockdown was confirmed by 90% of the women compared with 82% men. More women than men were solely responsible for domestic chores (38.7% v 23.7%), managed their children's education (74% v 31%), and felt an adverse impact of the pandemic on their professional work (60.8% v 42.6%). Fewer women's spouses (57/359) than men's (174/594, P = .00001) were forced to take leave or work reduced hours, and double the proportion of women (3.5% v 1.5%) had to quit their jobs to manage responsibilities at home.CONCLUSIONAs the COVID-19 pandemic and the lockdown measures threw newer challenges, more women physicians than men (81% v 63%) shouldered the burden of increased domestic work and childcare. This survey highlights the need to re-examine the specific challenges faced by women physicians and identify means to support and empower them.

Background and Aims: Ultrasonography (USG) is used to evaluate gastric residual volume (GRV); however, this technique may have inter-assessor variability. This study aimed to measure GRV in three groups of fasted patients 2 h after they received 200 mL of water, clear apple juice or apple-flavoured oral rehydration solution (ORS) and to determine inter-assessor reliability of USG-guided GRV measurement. Methods: We randomised 90 adult patients planned for elective cancer surgery, with no risk factors for delayed gastric emptying, to receive 200 mL of water, clear apple juice or apple-flavoured ORS after overnight fasting. Two hours later, two blinded assessors (a trained anaesthesiologist and a radiologist) independently determined USG-guided GRV. The primary outcome was GRV measured by the radiologist. The secondary outcome was inter-assessor correlation and agreement in GRV measurements. Results: There was no statistically significant difference in median GRV between groups (apple-flavoured ORS 74.8 mL, apple juice 63.7 mL, and water 62.1 mL, P = 0.11). We found poor correlation between measurements of radiologist and anaesthesiologist (Intra-class correlation coefficient 0.3, 95% confidence intervals 0.09 to 0.48, P value 0.002). The average (mean) bias was 5.4 mL (standard deviation 42.3 mL) and the 95% limits of agreement were -79.2 ml to +90 ml. Conclusion: Patients receiving 200 mL of water, clear apple juice or apple-flavoured ORS had comparable GRV after 2 h. There was poor correlation and agreement between GRV measurements of different assessors, indicating that more training may be required for anaesthesiologists to attain proficiency in the quantitative assessment of GRV.

Clinical research is an essential part of evidence-based medicine. The conduct of high-quality clinical research requires the backing of strong infrastructure, especially well-trained clinical research professionals. Tata Memorial Centre is the largest public cancer center in India and has been offering a Masters degree in Clinical Research since 2014. In this article, we look at the need for clinical research training, the evolution of this course and the impact it has had on clinical research capacity in India

The previous two articles in this series gave an overview of the methodology of systematic reviews and meta-analysis. In this third and concluding article, we look at the different types of biases that can confound the results of a meta-analysis and briefly describe some special types of meta-analysis.

Randomized controlled trials are the gold standard for determining the efficacy of a new intervention. Trials conducted for regulatory approval of an intervention compare the effect of the intervention with the standard of care or placebo to demonstrate efficacy. Randomization attempts to ensure that all known and unknown confounding factors are evenly distributed between the groups, and that the groups will be comparable at the end of the study, so that any inter-group differences in outcomes can be attributed to the intervention. However, in reality, intercurrent events may impact the assessment and subsequent interpretation of the outcome of interest. To address this, International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) in 2017, released an addendum to the E9 guideline (ICH E9 R1) putting forth the concept of Estimands and Sensitivity Analysis in Clinical Trials. This addendum addresses how these intercurrent events are to be handled using the Estimand concept, which is now expected to be detailed in a separate section of the study protocol. In this paper, we discuss what estimands are, and their likely impact on how regulatory trial protocols and their statistical analyses plans are written and implemented. We also look at the application of the concept of estimands to routine clinical practice.

The coronavirus disease-19 pandemic has affected all aspects of health care including clinical research, as the focus of health-care systems has shifted to maintaining essential care. The impact on clinical research has been profound. In this article, we have enlisted the multiple challenges faced by investigators and sites in carrying out clinical research activities during this crisis and the steps which can be taken by them to reduce the impact of this evolving pandemic on clinical research.

A systematic review is a form of secondary research that answers a clearly formulated research question using systematic and defined methods to identify, collect, appraise, and summarize all the primary research evidence on that topic. In this article, we look at meta-analysis – the statistical technique of combining the results of studies included in a systematic review.

Background and Aims: The aim of this study was to compare the efficacy of McGRATH series 5 videolaryngoscope (VL) with Macintosh laryngoscope for nasotracheal intubation (NTI) in patients without anticipated difficult airways undergoing head and neck cancer surgeries. Material and Methods: We randomized 60 adult patients for NTI by experienced anesthetists with either Macintosh laryngoscope or McGRATH series 5 VL (VL group). The primary objective was to compare time taken for intubation (TTI). The secondary objectives included success rates, number of attempts, need for optimization maneuvers, Cormack and Lehane (CL) grade, and percentage of difficult intubations. Results: The mean TTI in the VL group was 43 (±10.6) versus 75 (±38.0) s in the Macintosh group (99% CI: 12.5; –51.6 s; P < 0.001). The overall intubation success rate was 100% in both groups. All 29 (100%) patients in the VL group were intubated in the first attempt versus 26 (86%) patients in the Macintosh group (99% CI –5; 33%; P = 0.11). In the Macintosh group, 20 (66%) patients needed optimization maneuver versus none in the VL group (99% CI 40; 91%; P < 0.001). In the VL group, 28 (96%) patients had a CL grade 1 view versus 9 (31%) in Macintosh group (99% CI 38; 92%; P < 0.001). There were no difficult intubations in the VL group versus 3 (10%) in the Macintosh group (99% CI: 7; 28%; P = 0.237). There was no trauma to oropharyngeal structures in either group. Conclusion: The McGRATH series 5 VL has faster TTI, better glottic visualization, and less need for optimization maneuvers than the Macintosh laryngoscope for NTI in patients with unanticipated difficult airways, when performed by experienced anesthetists.

In this series on research study designs, we have so far looked at different types of primary research designs which attempt to answer a specific question. In this segment, we discuss systematic review, which is a study design used to summarize the results of several primary research studies. Systematic reviews often also use meta-analysis, which is a statistical tool to mathematically collate the results of various research studies to obtain a pooled estimate of treatment effect; this will be discussed in the next article.

In the fifth piece of this series on research study designs, we continue the discussion on interventional studies (clinical trials), in which the investigator decides whether or not a particular participant receives the exposure (or intervention). In this article, we take a closer look at several features which are important to ensure that the findings of such a study represent the real effect of an intervention, such as allocation concealment, blinding, compliance to intervention, the use of co-interventions and participant dropout rate.

In analytical observational studies, researchers try to establish an association between exposure(s) and outcome(s). Depending on the direction of enquiry, these studies can be directed forwards (cohort studies) or backwards (case–control studies). In this article, we examine the key features of these two types of studies.

Diagnostic tests are used to identify subjects with and without disease. In a previous article in this series, we examined some attributes of diagnostic tests – sensitivity, specificity, and predictive values. In this second article, we look at likelihood ratios, which are useful for the interpretation of diagnostic test results in everyday clinical practice.

In the previous two articles in this series on biostatistics, we examined the properties of diagnostic tests and various measures of their performance in clinical practice. These performance measures vary according to the cutoff used to distinguish the diseased and the healthy. We conclude the series on diagnostic tests by looking at receiver operating characteristic curves, a technique to assess the performance of a test across several different cutoffs, and discuss how to determine an optimum cutoff.

Background and Aims: In 2007, the World Health Organization (WHO) implemented the Surgical Safety Checklist (SSC), which has enhanced the communication between the surgical team members, improved outcomes, decreased complications, and improved patient safety. However, for the checklist to be effective, proper implementation and compliance with the checklist are imperative. The aim of this study was to evaluate the quality of implementation of the WHO SSC during elective surgery at a tertiary referral cancer hospital in India. Material and Methods: In this prospective observational study, a trained research nurse passively observed the implementation of selected items from the modified version of the WHO SSC during elective surgeries and evaluated the compliance with the checklist, percentage of items for which the use of the SSC prompted an action, and level of interaction between the key team players during the conduct of the checklist. Results: We studied 200 surgeries for each part of the SSC. Compliance was 200 (100%), 156 (78%), and 153 (76.5%) for the first, second, and third part of the SSC, respectively. All the three parts were mostly initiated by surgeons [197 (98.5%), 92 (59%), and 136 (88.9%), respectively]. Overall, 131/2200 (5.95%) items in the checklist were carried out only after being prompted during the conduct of the checklist. The interaction between all three representatives was found in only 265/509 (52%) cases. Conclusion: The quality of implementation of the SSC was found to be suboptimal, with a definite scope for improvement. Compliance with all items on the checklist and active participation by all team members are crucial for successful implementation of the checklist.

In this article in our series on common pitfalls in statistical analysis, we look at some of the attributes of diagnostic tests (i.e., tests which are used to determine whether an individual does or does not have disease). The next article in this series will focus on further issues related to diagnostic tests.

In the fourth piece of this series on research study designs, we look at interventional studies (clinical trials). These studies differ from observational studies in that the investigator decides whether or not a participant will receive the exposure (or intervention). In this article, we describe the key features and types of interventional studies.

One of the first steps in planning a research study is the choice of study design. The available study designs are divided broadly into two types – observational and interventional. Of the various observational study designs, the descriptive design is the simplest. It allows the researcher to study and describe the distribution of one or more variables, without regard to any causal or other hypotheses. This article discusses the subtypes of descriptive study design, and their strengths and limitations.

Logistic regression analysis is a statistical technique to evaluate the relationship between various predictor variables (either categorical or continuous) and an outcome which is binary (dichotomous). In this article, we discuss logistic regression analysis and the limitations of this technique.

Agreement between measurements refers to the degree of concordance between two (or more) sets of measurements. Statistical methods to test agreement are used to assess inter-rater variability or to decide whether one technique for measuring a variable can substitute another. In this article, we look at statistical measures of agreement for different types of data and discuss the differences between these and those for assessing correlation.

Background and Aims: Evidence-based medicine (EBM) is defined as the use of scientifically proven evidence for delivering best possible health care to patients. Despite growing emphasis on the need for EBM-based practice, acceptability, and perceptions toward EBM might differ among health professionals. The objective of this study was to assess the attitude, knowledge, and current practices of EBM among perioperative care health professionals in India. Material and Methods: This was a single point paper-based questionnaire survey carried out in February 2014 among delegates registered for an EBM conference on “perioperative care” held at a Tertiary referral Cancer Centre in India. Participation was voluntary and respondents were given the option of remaining anonymous. Results: Out of 190 questionnaires, 123 (65%) were returned. Most respondents (98%) agreed that practicing EBM improved patient care. The need to follow departmental protocols (22%) worries about the cost of implementing new treatments (20%) and inadequate skills to critically appraise articles (16%) accounted for major barriers in implementing EBM in clinical practice, with only 15% of respondents stating reluctance to change set practice. “Randomized controlled trial” and “number needed to treat” were the best and least understood EBM terms. Regarding awareness of 10 commonly used EBM-based guidelines in perioperative medicine, the percentage of correct responses ranged from 20% to 88%. Conclusion: Although most respondents agreed that practicing EBM improved patient care, many of them showed a low level of awareness regarding fundamental aspects of EBM. In addition to encouraging implementation of EBM, there should be increased focus on training in EBM methods.

There are several types of research study designs, each with its inherent strengths and flaws. The study design used to answer a particular research question depends on the nature of the question and the availability of resources. In this article, which is the first part of a series on “study designs,” we provide an overview of research study designs and their classification. The subsequent articles will focus on individual designs.

Background and Aims: The incidence of intra-operative awareness with explicit recall in the Western world has been reported to be between 0.1% and 0.2% in the general surgical population and up to 1-2% of patients at high risk for this complication. Awareness in the Indian population has never been studied; we therefore wanted to detect the incidence of awareness in patients who were at high risk of experiencing awareness during surgery in our population. Material and Methods: We conducted a prospective single-center observational study at a 600-bedded tertiary cancer care referral hospital. We recruited adult patients posted for major cancer surgery who were considered to be at high risk for awareness. These patients were interviewed at three time-points using the structured modified Brice interview questionnaire. The primary outcome studied was the incidence of definite intra-operative awareness. Results: A total of 934 patients were included in the final analysis of which none reported awareness. Using the rule of three (Hanley and Lippman-Hand) we conclude that the upper 95% confidence interval for the incidence of awareness in this population is

Correlation is a statistical technique which shows whether and how strongly two continuous variables are related. In this article, which is the eighth part in a series on ′Common pitfalls in Statistical Analysis′, we look at the interpretation of the correlation coefficient and examine various situations in which the use of technique of correlation may be inappropriate.

In a previous article in this series, we explained correlation analysis which describes the strength of relationship between two continuous variables. In this article, we deal with linear regression analysis which predicts the value of one continuous variable from another. We also discuss the assumptions and pitfalls associated with this analysis.

In the previous article in this series on common pitfalls in statistical analysis, we looked at the difference between risk and odds. Risk, which refers to the probability of occurrence of an event or outcome, can be defined in absolute or relative terms. Understanding what these measures represent is essential for the accurate interpretation of study results.

During the conduct of clinical trials, it is not uncommon to have protocol violations or inability to assess outcomes. This article in our series on common pitfalls in statistical analysis explains the complexities of analyzing results from such trials and highlights the importance of "intention-to-treat" analysis.

Background: Allogenic blood transfusion is associated with several potential complications, especially in patients with cancer. The objective of this prospective single-centre study was to identify the rates of perioperative blood transfusion and overtransfusion in a tertiary-level cancer hospital. Methods: Between March and May 2008, we studied all adult patients undergoing elective major cancer surgery under anaesthesia and recorded intra- and immediate post-operative (within 24 h) blood transfusions and post-operative investigations. Overtransfusion was defined as post-transfusion haemoglobin (Hb) exceeding 10 g/dL. Results: One hundred and eighty-six of 1175 (16%) patients received perioperative blood transfusion. The main trigger for intraoperative transfusion was blood loss exceeding the patient′s maximum allowable blood loss (92, 49%). Ninety-five (51%) transfused patients had post-transfusion Hb more than 10 g/dL. The rate of overtransfusion was not higher in patients who received single-unit transfusions. Conclusion: The perioperative transfusion rate in patients undergoing cancer surgery was 16%. More than half of these patients were overtransfused. Following this audit, point-of-care facilities for intraoperative haemoglobin measurement have been introduced.

In biomedical research, we are often interested in quantifying the relationship between an exposure and an outcome. “Odds” and “Risk” are the most common terms which are used as measures of association between variables. In this article, which is the fourth in the series of common pitfalls in statistical analysis, we explain the meaning of risk and odds and the difference between the two.

Ultrasound technology is a rapidly emerging science and the field of anaesthesia has not remained un-touched by its widespread applications. It is playing an increasing role in vascular access, in regional anaes-thesia for nerve blocks and as a transoesophageal echocardiography tool for cardiac imaging and viewing blood flows. It has special applications to assess the depth of epidural space in cases of difficult anatomy or in an otherwise high risk patient where interventional procedure is required. As the ultrasound guidance is becom-ing standard practice of future, anaesthesiologists need to develop a thorough understanding of this technol-ogy& practical skills by training themselves.

Neurological deficit is an uncommon but catastrophic complication of epidural anesthesia. Epidural hematomas and abscesses are the most common causes of such neurological deficit. We report the case of a patient with renal cell carcinoma with lumbar vertebral metastasis who developed paraplegia after receiving thoracic epidural anesthesia for a nephrectomy. Subsequently, on histo-pathological examination of the laminectomy specimen, the patient was found to have previously undiagnosed thoracic vertebral metastases which led to a thoracic epidural hematoma. In addition, delayed reporting of symptoms of neurological deficit by the patient may have impacted his outcome. Careful pre-operative investigation, consideration to using alternative modalities of analgesia, detailed patient counseling and stringent monitoring of patients receiving central neuraxial blockade is essential to prevent such complications.

Multiple testing refers to situations where a dataset is subjected to statistical testing multiple times - either at multiple time-points or through multiple subgroups or for multiple end-points. This amplifies the probability of a false-positive finding. In this article, we look at the consequences of multiple testing and explore various methods to deal with this issue.