As @Alexander already mentioned, you are looking for an approach that is called "individual participant/person/patient data meta-analysis" (IPD meta-analysis). He also refered to an article by Richard Riley, who has published a lot in this field. Please find below a collection of articles that I used for our advanced meta-analysis class:
Cooper, H., & Patall, E. A. (2009). The relative benefits of
meta-analysis conducted with individual participant data versus
aggregated data. Psychological methods, 14(2), 165–176.
doi:10.1037/a0015565
Curran, P. J., & Hussong, A. M. (2009). Integrative data analysis:
the simultaneous analysis of multiple data sets. Psychological
methods, 14(2), 81–100. doi:10.1037/a0015914
Lyman, G. H., & Kuderer, N. M. (2005). The strengths and limitations
of meta-analyses based on aggregate data. BMC Medical Research
Methodology, 5(1), 14.
(already mentioned) Riley, R. D., Lambert, P. C., & Abo-Zaid, G.
(2010). Meta-analysis of individual participant data: rationale,
conduct, and reporting. BMJ, 340(feb05 1), c221-c221.
doi:10.1136/bmj.c221
Riley, R. D., Lambert, P. C., Staessen, J. A., Wang, J., Gueyffier,
F., Thijs, L., & Boutitie, F. (2007). Meta-analysis of continuous
outcomes combining individual patient data and aggregate data.
Statistics in Medicine. doi:10.1002/sim.3165
Simmonds, M. C., Higgins, J. P., Stewart, L. A., Tierney, J. F.,
Clarke, M. J., & Thompson, S. G. (2005). Meta-analysis of individual
patient data from randomized trials: a review of methods used in
practice. Clinical Trials, 2(3), 209–217.
Stewart, L. A., & Tierney, J. F. (2002). To IPD or not to IPD?
Advantages and disadvantages of systematic reviews using individual
patient data. Evaluation and The Health Professions, 25(1), 76-97.
Best Answer
The purpose of using SMD is to uniform scale before they are combined. So if you already have same measurement scale, SMD is not necessary. According to this Cochrane page, the standardized mean difference is used as a summary statistic in meta-analysis when the studies all assess the same outcome but measure it in a variety of ways (for example, all studies measure depression but they use different psychometric scales). In this circumstance it is necessary to standardize the results of the studies to a uniform scale before they can be combined. The standardized mean difference expresses the size of the intervention effect in each study relative to the variability observed in that study.