Dear colleagues,

I am conducting a meta-analysis of in vitro studies, but I am facing challenges due to the variability in methodologies, as well as differences in doses and exposure times used across the included studies. I have the following questions and would greatly appreciate any guidance or recommendations:

1. Standardized Mean Difference (SMD): Is it appropriate to calculate the SMD to account for variations in measurement scales across studies? Would this approach be reliable for comparing studies with differing doses and exposure times?

2. Heterogeneity: What are the best practices for handling heterogeneity in in vitro data, especially when the methodologies differ substantially?

3. Risk of Bias Assessment: How can the risk of bias be systematically assessed in in vitro systematic reviews? Are there specific tools or frameworks that are commonly used for this purpose?

Any advice, references, or insights from your experience would be incredibly helpful. Thank you in advance for your time and assistance!

Best regards,