[R-meta] Mismatch between P-value and 95% CI in rma()

[Viechtbauer, Wolfgang (NP)]

Hi Adelina,

Can you provide a fully reproducible example? Without this, I cannot really tell what is going on.

Best,
Wolfgang

>-----Original Message-----
>From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-bounces using r-project.org] On
>Behalf Of Adelina Artenie
>Sent: Tuesday, 16 August, 2022 21:04
>To: r-sig-meta-analysis using r-project.org
>Subject: [R-meta] Mismatch between P-value and 95% CI in rma()
>
>Hi everyone,
>
>I am running a meta-regression analysis for which the outcome is a rate and
>several continuous moderator variables. I use rma() in metafor to estimate the
>incidence rate ratio (IRR) associated with a 1-unit increase in the moderator.
>
>If I specify test = "z", my understanding is that both the P-value and the 95%CI
>are estimated using the Wald test (so results should align). However, I see a
>small mismatch between the P-value and the 95%CI: the upper bound of the 95% CI
>is 1.00 (eg: IRR=0.97; 95%CI: 0.94 � 1.00), yet the P-value can be anywhere from
>P= 0.07 to P= 0.1, depending on the moderator. These P-values seem too high � I
>would expect them to be closer to 0.05.
>
>I wonder if I am making a mistake in my code or interpretation, or alternatively,
>if a mismatch like this could occur (though I�ve never encountered it before..) I
>wonder also if this can have anything to do with the log transformation.
>
>I rely on 95%CI when interpreting my results but I like to also present the P-
>value, and so I�d like to understand what is happening.
>
>Many thanks for your help.
>Best,
>Adelina Artenie
>
>**
>Code:
>My_rma <- rma(measure = "IRLN",
>                        xi = cases,
>                        ti = prs_yrs_100,
>                        add = 0.5,
>                        to = "only0",
>                        data = Incidence_dat,
>                        method = "DL",
>                        test = "z",
>                        slab = author,
>                        mods = ~ moderator )
>summary(My_rma)
>round(exp(coef(summary(My_rma))[-1,c("estimate", "ci.lb", "ci.ub")]), 2)