# Meta-analysis with only p-values

I am doing a systematic review on the risk factors that predict infection after liver and pancreatic surgery. These risk factors include parameters like age, sex, smoking, pre-operative chemo etc.

I have a number of studies but not all report their findings in the same way, so I am having trouble doing the meta-analysis. Some of the studies only report a p-value. Beyond simply counting the number of studies that have significant P-values for each risk factor, is there another way to derive an overall p-value for each risk factor?

• Do you know the direction of the effect? – Jeremy Miles Feb 10 '20 at 17:06
• You can work back from a p-value to a standardized difference and variance, if you know the sample size (and the direction). – Jeremy Miles Feb 10 '20 at 17:07
• I do know the direction of the effect and sample size. – Keno Feb 11 '20 at 11:13
• Here is a worked example using R: metafor-project.org/doku.php/tips:assembling_data_smd – Wolfgang Feb 11 '20 at 18:51

There are many ways to calculate an overall $$p$$-value: Edgington's method, Fisher's, Lancaster's, Stouffer, Tippett's and several others. They all have their advantages and disadvantages. Since you have tagged this R you may be interested to read the vignettes for the metap package available from CRAN which contains some guidance on the choice. It is too long to include here.