how to interpret the MR-PRESSO results

[arkyl]

Hi,
I am wondering how to interpret the MR-PRESSO results. I used "OUTLIERtest = TRUE, DISTORTIONtest = TRUE" as in the example.
Under "Main MR results", if for "Outlier-corrected" MR, I got a significant P-value, does that mean the MR result is significant after outlier removal? Or do I need to do any additional analysis?
Thanks much!

Yue

[kaanokay]

Hi @rondolab,

I'm interested in your package. Could you give more details about how to interpret MR-PRESSO results? Results are made of many different slot. I had 48 SNPs and outlier test found 17th, 31th, and 35th SNPs are outlier right? I should remove these SNPs, and then re-analyze my data with remained 45 SNPs? If you can explain to give examples, I'll be so appreciate for that.

Thanks.

My MR-PRESSO results:

[kaanokay]

[marieverbanck]

Hi @arkyl and @kaanokay ,

MR-PRESSO is a sequential method that comprises three components

1- Global test

MR-PRESSO applies an IVW MR model using all specified IVs and computes a global test for horizontal pleiotropy (H0: there is no horizontal pleiotropy). The global test provides a test statistic (residual sum of squares) and a P-value reported in:
$`MR-PRESSO results`$`Global Test`

2- Outlier test

If horizontal pleiotropy is detected in step 1, MR-PRESSO performs an outlier test for each IV and remove all offending IVs that are due to horizontal pleiotropy before running IVW MR without the detected outliers. The outlier test provides a test statistic (residual sum of squares) and a P-value for each IV reported in:
$`MR-PRESSO results`$`Outlier Test`

3- Distortion test

If horizontal pleiotropy is detected in step 1 and outliers are detected in step 2, MR-PRESSO performs a distortion test to test the difference in the causal estimates before and after outlier removal. The distortion test provides:

1. the list of the 'Outliers Indices' identified as outliers and excluded to calculate
2. the 'Distortion Coefficient' (in percent) and
3. its P-value.

These elements are reported in:
$`MR-PRESSO results`$`Distortion Test`

Synthesis of the results

The estimated causal effect (as well as standard error, test statistic and P-value) are reported for the raw MR analysis and the outlier-corrected MR analysis in
$`Main MR results`

NB: if no horizontal pleiotropy is detected or no outlier IVs are detected MR-PRESSO outputs NAs for the outlier-corrected analysis.

Best,
Marie

[kaanokay]

Hi @marieverbanck,

Thank you so much for your detailed explanation.

Bw.