In meta-analysis 3RCTs, why does the Cochrane h'book ref 17.7 discourage using means difference?

I tried performing a meta-analysis of single arm studies (i.e without controls) using openMeta-analyst which allowed me to combine the effect estimate in form of proportions. Different organ transplants with similar endpoint were included from various studies. I was able to obtain

1) the overall estimate of all organs

2) perform sub-group analysis to find the estimate for specific organs, timing of treatment(<7days and >7 days), study design and availability of insurance cover or not

3) Did meta-regression to assess impact of covariates like timing of treatment

My PI wants a direct comparison of the point estimates from the subgroups already meta-analyzed. Is this a good practice and how can I do this without controls? I thought of using one organ say heart as the intervention and liver as control and then including by the number of events/total number of subjects for studies that provided data. For the corresponding control or intervention without values (since this direct comparison was not done in individual studies), I used zero and then corrected with 0.5 automatically which the software handles pretty well. Is this an ideal way to go in order to obtain the RR or OR across different sub-groups?

Please see below a schema of what I did:

Study organ 1 organ 2

A 0/0 6/20

B 0/0 4/9

C 0/0 8/23

D 6/21 0/0

E 34/45 0/0

F 12/50 0/0

ABC don't have information on organ 1 while DEF don't have info on organ 2. I am hoping this set up can help me unravel the difference between organs for a specific outcome measured.

I would appreciate your urgent response.

Hi I am currently doing a systematic review and meta analysis comparing 3 PDE5 inhibitors for the treatment of erectile dysfunction, the studies are alll interventio vs placebo, however some

are flexible dosage and some are fixed dosage, how would I incorporate these dosages in a forest plot? Would I pool them all together? Or have two seperate forest plots, one competing fixed dosage and one comparing flexible dosage? Also I second question is would a traditional meta analysis or a network meta analysis Work best for my review? Bare in mind all trails compare against placebo

thanks

PLEASE guide me how can I use or even convert Mean(%) to Mean(mm)

I am pooling the effect size of a specific intervention. I am calculating the mean difference and 95% confidence interval scores. I came across an outcome measure expressed in Meters in some of these studies and expressed in Feet in one study.

Is it correct if I convert the mean and the standard deviation to Meters and I calculate the mean difference or should I calculate the standard mean difference as an alternative?

I carried out a Dersimonian-Laird random-effects meta-analysis using Cochrane (RevMan) software to create a summary effect estimate of weighted mean difference. I notice that the distribution of study effects (n=20) is negatively skewed. Do you recommend using the Permutation Method for non-parametric RE meta-analysis (e.g. Stata)? How skewed do the estimates have to be to require this form of RE meta-analysis. Thanks.

Hi All,

I am currently undertaking a systematic review. 19 studies were classified as studies awaiting classification.

I have contacted the authors. Several authors did not reply and a number of others replied stating that this abstract has not been published yet. For these studies, the decision is surely to include them in studies awaiting classification.

However, a number of authors indicated that although the abstract was not published as a paper, they have written one or more papers from the same study. Outcome measures are often different than those presented in the abstract identified during the search.

For the latter studies, would you still include them in the studies awaiting classification? How would you treat these conference abstracts?

Thanks,

Pasquale

Hi All,

I am currently undertaking a systematic review. Two of the studies, completed by nearly the same authors, seem to have used the same set of participants.

The differences mainly lies in the study design:

Study 1 included a double-blind, randomized, sham controlled trial (5 days/ week for 2 weeks) in twenty patients with 3:2 ratio. At baseline, each patient underwent a clinical evaluation. Assessments were then carried out immediately after either shaml or real stimulation (post-stimulation, T1), at one-month (T2) and at three-months follow-up (T3).

Study 2 included a randomized, double-blind, sham-controlled, crossover trial (5 d/wk for 2 weeks) in 20 patients with a 1:1 ratio. Each patient underwent a clinical evaluation before and after real or sham stimulation. A follow-up evaluation was performed at 1 and 3 months with a crossover washout period of 3 months. After the washout, After a washout period of 3 months after the last visit (i.e., T3), each patient received the opposite treatment (crossover phase)

and underwent the same standardized assessment as in the first

phase, at baseline, at 2 weeks, at 1 month, and at 3 months

Both studies made use of the same outcome measures and data analysis involves identical data analysis measures.

What is your view on the below:

1. Should both studies be included in the review?

Since the authors seem to have made use of the same participants (same research authors, same institution, identical sample size, same outcome measurements), could the inclusion of the two studies bias the findings of the review?

Thank you!

Pasquale

I am conducting a meta-analysis. One of the outcome measures I am examining is speed. In some studies it is expressed in m/s while in others it is expressed in seconds.

How could I pool these studies (using std. mean difference) knowing that as increasing values in seconds signify decreased speed while increasing values in m/s signify increased speed?

Since I have some studies that reported the continuous outcome as change from baseline and others that reported it as end of value score, is it possible to include both?