Background: The Checklist for the Reporting of Updated Guidelines (CheckUp) has recently been developed as a tool to evaluate the completeness of reporting the updating process in updated clinical guidelines (CGs). However, the reporting of updated CGs has not yet been systematically assessed yet.

Objectives: 1) To assess the completeness of reporting the updating process in a sample of updated CGs; and, 2) to explore the inter-observer reliability of the CheckUp.

Methods: We performed a systematic search to identify updated CGs, with a systematic review of the evidence, including at least one recommendation, and published in 2015. Three independent reviewers assessed each included CGs using CheckUp. This checklist includes 16 items that address 1) presentation of an updated guideline (6 items;2) editorial independence (3 items); and, 3) methodology of the updating process (7 items). We calculated the median score per item, per domain, and overall. We determined the intraclass coefficient (ICC) and 95% confidence interval (95% CI).

Results: Sixty CGs were included. The median score per domain was 3 (range 1-6) for presentation, 2.5 (range 0-3) for editorial independence, and 4.5 (range 0-7) for methodology. The median overall score was 10 (range 5-16). CGs developed by a European or international organisation obtained a higher overall score compared to American and Asian ones. The overall agreement among the three reviewers was adequate (ICC 0.88; 95% CI 0.75-0.95).

Conclusions:The reporting of updating process in updated CGs is suboptimal. CheckUp can be used to inform guideline developers to improve the reporting of updated CGs.