Complex sentence: Some CTUs specialise in different methodologies (for example Randomised controlled Trials, cluster randomised trials, surgical trials, health services research) and some specialise in one disease type, whereas others are generic units.
Split into simpler sentences: Some CTUs specialise in different methodologies, such as randomised controlled trials, cluster randomised trials, surgical trials, and health services research. Some specialise in one disease type, whereas others are generic units.