Is it necessary to adjust the weight of a study included in a meta-analysis if the study provides two different results for the same patient cohort?

08 February 2024 1 8K Report

Good afternoon, everyone!

I plan to investigate the effect of Trendelenburg position on the quantitative measure "X". We have the following results:

1) Study 1: 30 patients in supine position have the value of the parameter "X" = 69+-10, same patients in Trendelenburg position: "X" = 75+-12. The time after which values of the parameter "X" were recorded after the start of the Trendelenburg position was 1 minute.

2) Study 2: 40 patients in the supine position: "X" = 86+-11, same patients in the Trendelenburg position: "X" = 105+-16. The time after which values of the parameter "X" were recorded after the start of the Trendelenburg position was 1 minute.

AND same 40 patients in the Trendelenburg position have the value of the parameter "X"= 95+-14, BUT the time after which values of the parameter "X" were recorded after the start of the Trendelenburg position was 10 minutes, instead of 1 min.

In fact, we have 3 observations for one outcome, but 2 of them are from the same cohort of patients in the Study 2.

How can we take this into account to adjust the "weight" of each of the two results in the second study?

Would it be correct to reduce the sample size for the second and third observations to 20 (40/2) when entering primary data for meta-analysis into programs such as Stata or RevMan?

Deborah J Hilton

Good afternoon, I have only used Revman once a long time ago to add a study done in Guinea Bassau to the cochrane review on antibiotics for the prevention of the complications associated with measles. I can't recall a lot of this now - it is a long time ago & now that review has been redone so my name was knocked off as co-author [I didn't assist with last review update]. However, my thoughts on your question from my limited knowledge of statistics is I wouldn't reduce sample to 20. Even though the same study group, but different amount of time after, it is more a repeat measure but changing one part of how your measure. I don't really know the answer to the question - sorry.

Badges
Science topic

More Petr Polyakov's questions See All

In PRIMER, is it possible to downweight certain taxa in multivariate community datasets to reflect uncertainty around identification??

I have a dataset with about 80 different species. As usual, some species are very easy to identify with certainty whereas others are more difficult, which means that I am less certain of my...

03 March 2021 8,066 4 View

How to get onecolumn document from standard IEEE ACCESS LateX template?

I have prepared a manuscript in IEEE Latex template, but for some purpose, I need to prepare a word file as well (detailed format is not required). Compared to two column .tex file, one column...

02 March 2021 1,830 3 View

Gel electrophoresis result for total RNA samples, 1.5 Agarose gel was used, How to improve the integrity of RNA?

Gel electrophoresis, RNA degradation, RNA extraction from fresh tissue

02 March 2021 5,433 5 View

How to grow E.coli on the low salt LB agar plate with 50 or 100ug/ml of Blasticidin?

Hello, I would like to ask how to grow E.coli which resists 50 or 100ug/ml of Blasticidin. I have tried many methods by using low salt Luria-Bertain(LB) agar plate. However, no colonies grow. Let...

01 March 2021 2,027 2 View

OpenBCI eeg--has anyone used them?

I'm looking to try out an off-the-shelf EEG set for some exploratory work. Curious if anyone has used the OpenBCI, and how much set-up work is required. I've heard they are more difficult to get...

01 March 2021 4,128 3 View

How to remove DCU and HOBT from my reaction?

I am doing a acid and a chiral amino alcohol reaction using DCC and HOBT in DCM or THF? Can anyone suggest me how to remove DCU and HOBT from a reaction mixture??

28 February 2021 2,153 1 View

1 nm thick MgO thin-film to be deposited on Si wafer using thermal evaporation. What will be the optimum deposition conditions?

Favourable conditions of base pressure, rate of deposition. Also, by which characterisation technique to be used to verify the thickness of the deposited film.

28 February 2021 3,640 3 View

How to eliminate Steady state error from Reinforcement learning genetic algorithm code?

The following code (see 1st 2 images attached) is used to produce PID controller values that are designed to control the system (G). The code finds the PID controller values (noted as k) by using...

28 February 2021 6,560 14 View

B-mercaptoethanol (BME) protocol?

Hi everybody, I have been running a multiplex IHC which allow me to stain the same tissue with different markers (Primary Ab + Secondary conjugated Ab) (AF487, AF555, AF647). Since I would like to...

27 February 2021 5,028 2 View

What is the suitable range of Sulfur content and Viscosity of Heavy fluid Oil that used in Kiln?

What is the disadvantages of high sulfur content to the ceramic burning process? and what is the effect of outranged viscosity?

24 February 2021 8,219 2 View

How optimize the Size Exclusion Chromatography?

Hello! I'll do a size exclusion chromatography, but I only have an open column, and I'll perform the peptide extraction from yeast, using buffer lysis (sodium phosphate 50 mM/NaCl 30 mM/DNAse and...

01 March 2021 2,215 2 View

No title

01 March 2021 3,905 5 View

What test should I use to compare two or three means, if data is not normally distributed but sample size is > 30 in each group?

I personally feel this as a most confusing question. As per my understanding, if sample size is > 30, and sample is skewed, we can still use paramteric approach, as it will follow Z...

01 March 2021 1,587 6 View

Is it necessary to report effect size (ES) in statistics of biomedical research given that we already report p values routinely?

Pls share your thoughts

01 March 2021 7,330 4 View

Why there are two peaks while using the mie plot of Silver nanoparticle?

Hi, I am trying to learn the theoretical modelling of silver nanoparticle using the Mie scattering theory. After that, I discovered a software named Mieplot developed by Philip Laven, where it...

25 February 2021 7,493 6 View

How to calculate Z (the number of molecules in a unit cell) for calculating theoretical density?

I am trying to calculate the theoretical density of my ceramics materials. I use the formula below to calculate the theoretical density: Theoretical density = (Molecular weight x No. of molecules...

24 February 2021 3,823 2 View

How to handle studies which report perfect effect sizes in a meta-analysis using Pearson's r?

I'm in the process of updating a meta-analysis and in one of the new studies, effect sizes are reported as Tau-U. Two of the effect sizes are reported as Tau-U = 1.00. I am using Andy Field's...

24 February 2021 2,265 3 View

Sample size determination for non-parametric tests?

How do I run a a priori sample size determination for non-parametric tests, like the Mann-Whitney U-test and the Kruskall-Wallis or other non-parametric tests that accord with the unpaired t-test...

24 February 2021 166 6 View

How to determine a priori sample size for t-test with unequal means?

I need to conduct a a priori sample size determinations for t-test with unequal means, but I don't know the sizes of the groups nor the ratio of both groups... Can I do a sample size determination...

24 February 2021 8,289 3 View

What are alternatives to factor analysis for a small sample?

My sample size is too small to conduct a factor analysis. I created my own psychometric scale for measuring Effectiveness of Support, which contains 38 items (4 sub-scales) Im really struggling...

23 February 2021 9,287 12 View