23 August 2018 - Associations between patient characteristics or treatments received and clinical outcomes are often first described using observational data, such as data arising through usual clinical care without the experimental assignment of treatments that occurs in a randomised clinical trial. 

These data based on usual clinical care are referred to by some as “real world” data. A key strategy for efficiently finding such associations is to use a case-control study. 

In a recent issue of JAMA Internal Medicine, Wang et al assessed the association between cardiovascular disease and use of inhaled long-acting β2-agonists or long-acting anti-muscarinic antagonists in chronic obstructive pulmonary disease (COPD), utilising a nested case-control study.

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