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Tammy Clifford - Canadian Agency for Drugs and Technologies in Health (CADTH). Ottawa, ON, CA

Tammy Clifford

Chief Scientist and Vice President, Evidence Standards | Canadian Agency for Drugs and Technologies in Health (CADTH)

Ottawa, ON, CANADA

Supporting evidence-informed decisions in Canadian health care as CADTH's Chief Scientist and Vice President, Evidence Standards.





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Evidence, ethics and quality - Tammy Clifford




Have you wondered how drugs and other healthcare interventions become available for use in the Canadian healthcare system? What factors go into these decisions and who's involved? How does the Canadian process compare to similar processes around the globe?

Dr Tammy Clifford is the Chief Scientist and Vice President, Evidence Standards at CADTH, a Canadian organization that assesses evidence on behalf of the health system, helping policy makers and practising clinicians determine what health interventions work and whether they provide value to our health care system. Tammy has more than a dozen years of progressive health leadership experience, including executive and senior management positions in academic and non-for-profit environments.

Trained as a PhD Epidemiologist, Tammy is a passionate, empowering leader with an accomplished track record of producing timely, relevant, high-quality health research that supports informed policy and practice decisions within the Canadian health care system. She has developed a keen understanding of real-world evidence needs, resulting from direct involvement as a scientist and as a respected leader of inter-disciplinary teams. Tammy is well-connected with the broader health research community, in Canada and globally. She remains actively involved in university teaching and graduate student supervision, mostly through the University of Ottawa's School of Epidemiology, Public Health & Preventive Medicine.

Industry Expertise (5)



Health Care - Services

Medical Devices


Areas of Expertise (11)


Evidence-Based Medicine


Health & Healthcare Law and Policy

health technology assessment

Systematic Reviews


Research Ethics

Randomized Controlled Trials

Peer Review

Women in Science

Education (3)

McGill University: BSc, Physiology 1992

McGill University: MSc, Occupational Health 1993

University of Western Ontario: PhD, Epidemiology & Biostatistics 2002

Affiliations (2)

  • Adjunct Professor, School of Epidemiology, University of Ottawa
  • Associate Editor, International Journal of Technology Assessment in Health Care

Languages (1)

  • English

Media Appearances (3)

Is robotic surgery worth the cost?

Healthy Debate  online


Interviewed to provide context surrounding topic of robotic surgery; spoke to the need for evidence to demonstrate impact of any health technology on outcomes that matter to patients, and to consider the opportunity costs associated with acquisition and ongoing maintenance of such big ticket items.

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How an Ottawa doctor's inventions are making health care faster and cheaper

Ottawa Citizen  online


Spoke to the need for technology developers to collect the evidence/data that will be required by regulators and payors to "make the case" that the technology works (on outcomes that matter to patients), and how it can help the health care system.

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Mind the Uncertainty Gap (video podcast)

IDEAL Collaboration - Oxford University  online


A 15 minute presentation delivered at the IDEAL Collaboration meeting in April 2017, at Oxford University. Comparing/contrasting the results of a handful of health technology assessments on robotic surgery.

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Articles (12)

Expediting evidence synthesis: exploring attitudes & perspections towards rapid reviews using Q methodology

Peer J


Rapid reviews expedite the knowledge synthesis process with the goal of providing timely information to healthcare decision-makers who want to use evidence-informed policy and practice approaches. A range of opinions and viewpoints on rapid reviews is thought to exist; however, no research to date has formally captured these views. This paper aims to explore evidence producer and knowledge user attitudes and perceptions towards rapid reviews.

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International Journal of Technology Assessment in Health Care


Rapid reviews are characterized as an accelerated evidence synthesis approach with no universally accepted methodology or definition. This modified Delphi consensus study aimed to develop a comprehensive set of defining characteristics for rapid reviews that may be used as a functional definition.

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Quality of conduct and reporting in rapid reviews: an exploration of compliance with PRISMA and AMSTAR guidelines

Systematic Reviews


Rapid reviews are an accelerated evidence synthesis approach intended to meet the timely needs of decision-makers in healthcare settings. Quality of conduct and reporting has been described in the rapid review literature; however, no formal assessment has been carried out using available instruments. The objective of this study was to explore compliance with conduct and reporting guidelines in rapid reviews published or posted online during 2013 and 2014.

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A third of systematic reviews changed or did not specify the primary outcome: a PROSPERO register study

Journal of Clinical Epidemiology


The primary outcomes from systematic review publications were compared with those reported in the corresponding PROSPERO records; discrepancies in the primary outcomes were assessed as upgrades, additions, omissions, or downgrades. Relative risks (RRs) and 95% confidence intervals (CI) were calculated to determine the likelihood of having a change in primary outcome when the meta-analysis result was favorable and statistically significant. Ninety-six systematic reviews were published. A discrepancy in the primary outcome occurred in 32% of the included reviews and 39% of the reviews did not explicitly specify a primary outcome(s); 6% of the primary outcomes were omitted. There was no significant increased risk of adding/upgrading (RR, 2.14; 95% CI: 0.53, 8.63) or decreased risk of downgrading (RR, 0.76; 95% CI: 0.27, 2.17) an outcome when the meta-analysis result was favorable and statistically significant. As well, there was no significant increased risk of adding/upgrading (RR, 0.89; 95% CI: 0.31, 2.53) or decreased risk of downgrading (RR, 0.56; 95% CI: 0.29, 1.08) an outcome when the conclusion was positive. We recommend review authors carefully consider primary outcome selection, and journals are encouraged to focus acceptance on registered systematic reviews.

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Network meta-analysis incorporating randomised controlled trials and non-randomised comparative cohort studies for assessing the safety and effectiveness of medical treatments

Systematic Reviews


Network meta-analysis is increasingly used to allow comparison of multiple treatment alternatives simultaneously, some of which may not have been compared directly in primary research studies. The majority of network meta-analyses published to date have incorporated data from randomized controlled trials (RCTs) only; however, inclusion of non-randomized studies may sometimes be considered. Non-randomized studies can complement RCTs or address some of their limitations, such as short follow-up time, small sample size, highly selected population, high cost, and ethical restrictions. In this paper, we discuss the challenges and opportunities of incorporating both RCTs and non-randomized comparative cohort studies into network meta-analysis for assessing the safety and effectiveness of medical treatments. Non-randomized studies with inadequate control of biases such as confounding may threaten the validity of the entire network meta-analysis. Therefore, identification and inclusion of non-randomized studies must balance their strengths with their limitations. Inclusion of both RCTs and non-randomized studies in network meta-analysis will likely increase in the future due to the growing need to assess multiple treatments simultaneously, the availability of higher quality non-randomized data and more valid methods, and the increased use of progressive licensing and product listing agreements requiring collection of data over the life cycle of medical products. Inappropriate inclusion of non-randomized studies could perpetuate the biases that are unknown, unmeasured, or uncontrolled. However, thoughtful integration of randomized and non-randomized studies may offer opportunities to provide more timely, comprehensive, and generalizable evidence about the comparative safety and effectiveness of medical treatments

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How can we improve the recognition, reporting and resolution of medical device-related incidents in hospitals?

BMC Health Services Research


To explore factors that influence and to identify initiatives to improve the recognition, reporting and resolution of device-related incidents. Semi-structured telephone interviews with 16 health professionals in two tertiary care hospitals were conducted. Purposive sampling was used to identify appropriate study participants. Transcribed interviews were read independently by one individual to identify, define and organize themes and verified by another reviewer. Themes related to incident recognition were the hospital staff's knowledge and professional experience, medical device performance and clinical manifestations of patients, while incident reporting was influenced by error severity, personal attitudes of clinicians, feedback received on the error reported. Physicians often discontinued using medical devices if they malfunctioned. Education and training and the implementation of registries were discussed as important initiatives to improve medical device surveillance in clinical practice. Results from the telephone interviews suggest that multiple factors that influence participation in medical device surveillance activities are consistent with results for medical errors as reported in previous studies. The study results helped to propose a conceptual framework for a medical device surveillance system in a hospital context that would enhance patient safety and health care delivery.

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Factors that influence the recognition, reporting, and resolution of incidents related to medical devices and other healthcare technologies: a systematic review

Systematic Reviews


Medical devices have improved the treatment of many medical conditions. Despite their benefit, the use of devices can lead to unintended incidents, potentially resulting in unnecessary harm, injury or complications to the patient, a complaint, loss or damage. Devices are used in hospitals on a routine basis. Research to date, however, has been primarily limited to describing incidents rates, so the optimal design of a hospital-based surveillance system remains unclear. Our research objectives were twofold: i) to explore factors that influence device-related incident recognition, reporting and resolution and ii) to investigate interventions or strategies to improve the recognition, reporting and resolution of medical device-related incidents.

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Rapid reviews: an emerging approach to evidence synthesis in health technology assessment

International Journal of Technology Assessment in Health Care


Increasingly, healthcare decision makers demand quality evidence in a short timeframe to support urgent and emergent decisions related to procurement, clinical practice, and policy. Health technology assessment (HTA) producers are responding by developing innovative approaches to evidence synthesis that can be executed more quickly than traditional systematic review. These approaches, and the broader implications they bring to bear on health decision making and policy development, however, are generally neither well-understood nor well-described. This study intends to contribute to an emerging literature around methodological approaches to rapid review in HTA by outlining those developed and implemented by the Canadian Agency for Drugs and Technologies in Health (CADTH).

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Complementary and alternative medicine use by pediatric specialty outpatients



OBJECTIVE: Complementary and alternative medicine (CAM) use is high among children and youth with chronic illnesses. The objective of this study was to assess the prevalence and patterns of CAM use in 10 subspecialty clinics in Canada and to compare CAM use between 2 geographically diverse locations. METHODS: This survey was carried out at 1 Children’s Hospital in western Canada (Edmonton) and 1 Children’s Hospital in central Canada (Ottawa). Questionnaires were completed by parents in either French or English. RESULTS: Although demographic characteristics of the 2 populations were similar, CAM use at the western hospital was 71% (n = 704) compared with 42% (n = 222) at the central hospital (P < .0001). Most respondents agreed or strongly agreed that they feel comfortable discussing CAM in their clinic. The most common CAM products currently used were multivitamins/minerals, herbal products, and homeopathic remedies. The most common CAM practices currently used were massage, chiropractic, relaxation, and aromatherapy. Eighty adverse effects were reported, and 55 (68.8%) of these were self-assessed as minor. CONCLUSIONS: Results of this study indicate that CAM use is high among pediatric specialty clinic outpatients and is much greater in the western than in the central hospital. Most respondents felt that their CAM use was helpful with few or no harms associated. Many patients, using CAM alongside their conventional medicines, are still not discussing their CAM use with their physicians and are increasing the likelihood for potential interactions and preventable harms.

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Gender issues: Do as I say, not as I do?

International Journal of Technology Assessment in Health Care


An invited commentary to accompany an empirical report on how (poorly) HTA agencies handle gender equity issues.

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Factors influencing breastfeeding choices in a southwestern Ontario community

Journal of Human Lactation


Factors associated with full breastfeeding (FBF) at 1 week and at 6 months postpartum were examined in a cohort of 856 mother-infant dyads. Questionnaires were mailed at 4 time points over the first 6 months postpartum. At 1 week, 68% of infants were FBF; at 6 months, 23% were FBF. Factors significantly associated with FBF at 1 week were hospital of delivery, residing with a smoker, maternal shiftwork during pregnancy, and having no prior breast-feeding experience. Cox proportional hazards regression analysis showed that residing with a smoker, having consumed caffeine during pregnancy, reporting elevated maternal trait anxiety at 1 week postpartum, having been employed full-time outside the home prior to delivery, and having received anesthesia/analgesia during labor/delivery were associated with earlier cessation of FBF, whereas not having previous breastfeeding experience predicted its continuation. Although most mothers are breastfeeding early on, a number of factors adversely affect its successful continuation.

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IDEAL framework for surgical innovation 1: the idea and development stages

BMJ (British Medical Journal)


IDEAL is a framework for evaluations of surgical innovations, which follow a distinct development pathway differing from the approach developed for pharmacological interventions. Many pathway and evaluation challenges are shared by other interventional therapies, requiring individual therapist skills and customisation of treatment to the individual, partly through medical devices. This paper provides an overview of the IDEAL framework and recommendations, and focuses on the first two stages: idea and development.

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