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Retrospective Analyses of Potential Interventions and Determinants for COVID-19

An international collaborative programme to evaluate non-randomised comparative studies of treatments for COVID-19 and prognostic factors


Repurposed medications with postulated activity against COVID-19 have been used in clinical practice variably in countries around the world, to treat Covid-19 patients, based largely on anti-viral activity, without good evidence of clinical effectiveness. Some drugs taken chronically for other diseases have been proposed to worsen the prognosis of COVID-19 patients.

A few large international randomized unblinded adaptive trials began in late March 2020 such as SOLIDARITY, DISCOVERY, and RECOVERY, as well as many smaller trials to test these medications. They may require several months to declare ´proof beyond reasonable doubt´ for effectiveness, futility, or harm.

Randomized controlled trials (RCT) provide the most unbiased evidence of treatment effects although unblinded RCTs may harbour greater post-baseline biases than blinded RCTs. However, non-randomised comparative studies can complement RCTs with data on patients excluded from randomized trials, uncommon safety events and greater statistical power.

Non-randomised comparative studies need careful design and analysis. There are some examples of non-randomised comparative studies producing the same results for benefits of treatment as RCTs. However, there are many examples to the contrary.
Many of the registered non-randomised COVID-19 comparative studies have similar aims but are using different methodologies, analytical designs, and varying sample sizes. This may result in differing results for the same questions, as with some reported RCTs.

Results of prognostic factors and scores emerging from these studies may also vary and require replication.
Therefore, our international study team will seek to use the experience of analysing a dataset of hospitalized COVID-19 patients of treatments and prognostic factors to help draw more robust and reliable results from non-randomised comparative studies of treatment effectiveness and safety and of prognostic factors and scores.


Our activities include:

– Non-randomised comparative retrospective cohort analyses of treatments in hospitalised COVID-19 patients in Spain.
– A ´real-time´ systematic review of non-randomised comparative studies of treatments for hospitalised patients with COVID-19 with requests for collaboration from study groups.
– Meta-analysis of non-randomised comparative studies of treatments in hospitalised COVID-19 patients.
– Seek to homogenise non-randomised comparative analyses of treatments in hospitalised COVID-19 patients where there are discrepant results between studies by collaboration with other study groups
– Comparison of non-randomised comparative studies of treatments in hospitalised COVID-19 patients and RCTs, cumulatively as these studies are published.

Our projects are registered in the EUPAS register and PROSPERO register.

We welcome enquires and opportunities for collaboration that will help the endeavour to combat this disease.

Our Core Team

There is an initial core team for this programme formed by the following experts:

Nawab Qizilbash
MRCP MSc DPhil(Oxon), Senior Clinical Epidemiologist, OXON Epidemiology, Madrid and Honorary Associate Professor, London School of Hygiene & Tropical Medicine

Stuart Pocock

PhD, Professor of Medical Statistics, London School of Hygiene & Tropical Medicine and Data Monitoring Committee member of the COVID-19 DISCOVERY trial

José Ignacio Méndez Rubio
MPH, Director of Data Analytics & HEOR, OXON Epidemiology, Madrid

Jesús López Arrieta

MD, Head of Geriatrics, Hospital Cantoblanco-La Paz, Madrid

Macarena Garrido-Estepa

MSc PhD, Science and Innovation Ministry, Madrid

Rafael Herruzo Cabrera

Professor of Preventive Medicine and Public Health, Universidad Autónoma de Madrid

Bélène Podmore
MPH PhD, Epidemiologist and Systematic Reviewer, OXON Epidemiology, Madrid

José M. Castellano
MD, PhD, Scientific Director, HM Hospitals, Madrid, Spain.

Ongoing Projects

Non-randomised comparative studies of treatments for COVID-19 and prognostic factors


Retrospective Cohort Analysis: Treatments for COVID-19


Meta-analysis of non-randomised treatment studies

Contact our core team