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Response to: ‘Catching the falling star: points to consider when using propensity scores’ by Ouyang et al
  1. Sytske Anne Bergstra1,
  2. Cornelia F Allaart1,
  3. Robert B M Landewé2,3
  1. 1 Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands
  2. 2 Amsterdam Rheumatology & Immunology Center, Amsterdam, The Netherlands
  3. 3 Zuyderland Medical Center, Heerlen, The Netherlands
  1. Correspondence to Sytske Anne Bergstra, Department of Rheumatology, Leiden University Medical Center, Leiden 2333 ZA, The Netherlands; s.a.bergstra{at}

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We would like to thank Dr Ouyang1 for his thoughtful response to our article, including additional suggestions regarding the use of the multiple (or generalised) propensity score (PS), which we are sure will be helpful for other researchers who plan to use this technique.2 We agree with the mentioned suggestions and will provide some additional clarifications.

Like virtually every method used to adjust for bias in observational data, a multiple PS is dependent on the ignorability assumption and assumes that all important confounders are measured and included. Although in practice it is probably impossible to know all confounders, this emphasises the importance of …

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  • Handling editor Josef S Smolen

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Provenance and peer review Commissioned; internally peer reviewed.

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