Evidence map›Paper›PMID 33188930›Full record

ArticleContemporary clinical trials2020

Causal inference methods for small non-randomized studies: Methods and an application in COVID-19.

Sarah Friedrich, Tim Friede

Open access · greenAbstract read
In one paragraph

Article in Contemporary clinical trials, 2020. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 7 papers.

0numbers the graph read from it
0cells of the map it votes in
7citing papers in PubMed
0.2field-weighted citation impact, top 43% of its field
1 · What the graph read from it

What it found

Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.

The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.

2 · The registry

The trial behind it

Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.

Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.

3 · Its place in the literature

Who cites it

7 citing papers in PubMed, 1 citations in OpenAlex.

  1. Sex-related variations in platelet reactivity in presence or absence of antiplatelet therapy.European heart journal. Cardiovascular pharmacotherapy · 2025
    Article
  2. Article
  3. Article
  4. Article
  5. On the role of data, statistics and decisions in a pandemic.Advances in statistical analysis : AStA : a journal of the German Statistical Society · 2022
    Article
  6. Article
  7. Guest editors-in-chief note to COVID-19 special issue.Contemporary clinical trials · 2021
    Article
4 · The record

Corrections and comments

PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.

5 · Who and what money

Authors and funding

2 authors at 1 institution in 1 country.

Sarah FriedrichDepartment of Medical Statistics, University Medical Center Göttingen, Humboldtallee 32, 37073 Göttingen, Germany. Electronic address: sarah.friedrich@med.uni-goettingen.de.
Tim FriedeDepartment of Medical Statistics, University Medical Center Göttingen, Humboldtallee 32, 37073 Göttingen, Germany. Electronic address: tim.friede@med.uni-goettingen.de.
University of Göttingen · DE

Funding

No grant is acknowledged in the PubMed record.

6 · The paper itself

Abstract

The usual development cycles are too slow for the development of vaccines, diagnostics and treatments in pandemics such as the ongoing SARS-CoV-2 pandemic. Given the pressure in such a situation, there is a risk that findings of early clinical trials are overinterpreted despite their limitations in terms of size and design. Motivated by a non-randomized open-label study investigating the efficacy of hydroxychloroquine in patients with COVID-19, we describe in a unified fashion various alternative approaches to the analysis of non-randomized studies. A widely used tool to reduce the impact of treatment-selection bias are so-called propensity score (PS) methods. Conditioning on the propensity score allows one to replicate the design of a randomized controlled trial, conditional on observed covariates. Extensions include the g-computation approach, which is less frequently applied, in particular in clinical studies. Moreover, doubly robust estimators provide additional advantages. Here, we investigate the properties of propensity score based methods including three variations of doubly robust estimators in small sample settings, typical for early trials, in a simulation study. R code for the simulations is provided.

Indexed as

COVID-19 Drug TreatmentAntiviral AgentsCausalityClinical Trials as TopicCOVID-19HumansHydroxychloroquinePandemicsPropensity ScoreSample SizeSARS-CoV-2Antiviral AgentsHydroxychloroquineCausal inferenceCOVID-19Propensity scoreSmall samples

Identifiers

PMID33188930
PMCPMC7834813
OpenAlexW3046779276

What OpenQuestion holds

Textmetadata
Read underepoch 390

Registered trials

None linked

Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.