MBNMAdose outputs: Relative effects, forest plots and rankings"

In MBNMAdose: Dose-Response MBNMA Models

library(MBNMAdose)
#devtools::load_all()
library(rmarkdown)
library(knitr)
library(dplyr)

knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>",
  fig.width = 7,
  fig.height = 5,
  include=TRUE,
  tidy.opts=list(width.cutoff=80),
  tidy=TRUE
)

For looking at outputs from MBNMAdose we will demonstrate using results from an Emax MBNMA on the triptans dataset:

tripnet <- mbnma.network(triptans)
trip.emax <- mbnma.run(tripnet, fun=demax(emax="rel", ed50="rel")) 

Estimating relative effects

It may be of interest to calculate relative effects between different doses of agents to obtain outputs that are more similar to those from standard NMA. A benefit of dose-response MBNMA is that relative effects between doses that have not been explored in trials can still be compared.

Relative effects can take the form of odds ratios, mean differences or rate ratios, depending on the likelihood and link function used in a model. Estimating relative effects can be particularly helpful for dose-response functions where parameter interpretation can be challenging (e.g. splines, fractional polynomials).

The get.relative() function allows for calculation of relative effects between any doses of agents as specified by the user. This includes doses not available in the original dataset, as these can be estimated via the dose-response relationship. Optional arguments allow for relative effects to be estimated at specific effect modifier values (if meta-regression incorporated into MBNMA model), calculation of 95% prediction intervals rather than 95% credible intervals (the default), and for the conversion of results from the log to the natural scale. The resulting relative effects can also be ranked (see [Ranking] for more details).

# Specify treatments (agents and doses) for which to estimate relative effects
treats <- list("Placebo"=0,
               "eletriptan"= 1,
               "sumatriptan"=2,
               "almotriptan"=1)

# Print relative effects on the natural scale
rels <- get.relative(trip.emax, treatments = treats, eform=TRUE)
print(rels)

# Rank relative effects
rank(rels)

get.relative() can also be used to compare results between two different models by specifying which model's relative effects should be presented in the lower left diagonal (lower.diag) of the table, and which should be presented in the upper right diagnoal (upper.diag).

This can be used to compare relative effects estimated by MBNMA models fitted with different dose-response relationships, or to compare MBNMA estimates with NMA estimates.

nma <- nma.run(tripnet) # NMA (consistency) model
ume <- nma.run(tripnet, UME=TRUE) # UME (inconsistency) model

# MBNMA consistency and NMA consistency odds ratios compared 
consistency <- get.relative(lower.diag=trip.emax, upper.diag=nma,
                            treatments = treats, eform=TRUE)
print(consistency)

It can also be used to compare NMA or MBNMA consistency models with Unrelated Mean Effects (UME) inconsistency models. A UME model only parameterises direct comparisons within the network and so can be used to test the consistency assumption ([Checking for consistency][3-consistencychecking.html]). Note that if a UME model is fitted, comparisons for which there is no direct evidence will not have relative effects estimated for them.

# MBNMA consistency and NMA inconsistency log-odds ratios compared
inconsistency <- get.relative(lower.diag=trip.emax, upper.diag=ume,
                            treatments = treats, eform=FALSE)
print(inconsistency)

Forest plots

Forest plots can be easily generated from MBNMA models using the plot() method on an "mbnma" object. By default this will plot a separate panel for each dose-response parameter in the model. Forest plots can only be generated for parameters which are modelled using relative effects and that vary by agent/class.

plot(trip.emax)

Ranking

Rankings can be calculated for different dose-response parameters from MBNMA models by using rank() on an "mbnma" object. Any parameter monitored in an MBNMA model that varies by agent/class can be ranked. A vector of these is assigned to params. lower_better indicates whether negative responses should be ranked as "better" (TRUE) or "worse" (FALSE).

ranks <- rank(trip.emax, lower_better = FALSE)
print(ranks)
summary(ranks)

The output is an object of class("mbnma.rank"), containing a list for each ranked parameter in params, which consists of a summary table of rankings and raw information on agent/class (depending on argument given to level) ranking and probabilities. The summary median ranks with 95% credible intervals can be simply displayed using summary().

Histograms for ranking results can also be plotted using the plot() method, which takes the raw MCMC ranking results stored in mbnma.rank and plots the number of MCMC iterations the parameter value for each treatment was ranked a particular position.

# Ranking histograms for Emax
plot(ranks, params = "emax")

# Ranking histograms for ED50
plot(ranks, params = "ed50")

Alternatively, cumulative ranking plots for all parameters can be plotted simultaneously so as to be able to compare the effectiveness of different agents on different parameters. The surface under cumulative ranking curve (SUCRA) for each parameter can also be estimated by setting sucra=TRUE.

# Cumulative ranking plot for both dose-response parameters
cumrank(ranks, sucra=TRUE)

References

MBNMAdose documentation built on Aug. 8, 2023, 5:11 p.m.