We performed a meta-research study by searching PubMed for comparative effectiveness observational studies evaluating therapeutic interventions using routinely collected data published in high impact factor journals from 01/06/2018 to 30/06/2020. We assessed the reporting of study design (i.e., eligibility, treatment assignment, and the start of follow-up). Risk of selection bias and immortal time bias was determined by assessing if the time of eligibility, treatment assignment and the start of follow-up were synchronised to mimic the randomisation following the target trial emulation framework.