The use of fixed study main effects in arm‐based network meta‐analysis

Methods of network meta‐analysis (NMA) can be classified as arm‐based and contrast‐based approaches. There are several arm‐based approaches, and some of these have been criticized because they recover inter‐study information and hence do not obey the principle of concurrent control. Here, we point out that recovery of inter‐study information in arm‐based NMA can be prevented by fitting a fixed main effect for studies. Advantages of arm‐based NMA are discussed.