In CovalenceResearch/sloper-public: A Simple Calculator to Project Dialysis Costs Based on eGFR Slopes

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slopeR

slopeR is a Shiny app designed to calculate time to dialysis and associated costs from estimated glomerular filtration rates (eGFR), for up to two treatments. The calculation is based on a 2021 article by Durkin and Blais. Please note that this Shiny app is implemented independently of these authors and any error in this app, which comes without any warranty, is our own.

How it works

The model developed by Durkin and Blais, which was implemented in this Shiny app, calculates eGFR trajectories using the acute and chronic slope from a cohort baseline eGFR value. Within the acute and chronic phase, respectively, eGFR is assumed to change linearly.

eGFR trajectories are calculated until they reach the user-specified eGFR threshold for dialysis initiation. The time it takes for eGFR to reach this threshold is combined with a user-specified cohort baseline age to calculate, for each treatment, the age at dialysis initiation.

This age is then used to find the corresponding estimate for remaining life expectancy in patients with end-stage renal disease (ESRD). These estimates came from the 2021 United States Renal Data Service Annual Data Report, Chapter 6: Mortality. For their remaining lifetime, patients are assumed to remain on dialysis so their remaining life time is the time to dialysis (TTD).

Costs are then calculated, for each treatment and eGFR slope, by multiplying TTD with annual costs of dialysis. These costs can then be compared across treatments and give an estimate of what total costs and cost savings would be with each treatment, based on its impact on eGFR.

How to use

Inputs

For using slopeR, you should have acute and chronic eGFR slopes, i.e., changes in eGFR between two time points. Such data are publicly available from clinical trials, but of course you can just explore assumptions for a treatment. Note that all eGFR values in slopeR are in the 'standard' eGFR unit: mL/min/1.73m².

In slopeR, you must specify the length of the acute phase and trial end, both in weeks. During the acute phase, the acute eGFR slope applies, between the end of the acute phase and the trial end, the chronic eGFR slope applies. In addition, you can explore lower and higher values than the main estimate. These work exactly the same way as the main estimate but save you some time by allowing you to investigate three values at once for a specific treatment. You can also specify names for each treatment to have table and figure outputs labelled specifically to your case.

You must also specify two population parameters for the cohort you're interested in: the baseline age and the baseline eGFR value. You also need to specify at which eGFR threshold dialysis is initiated.

Finally, you must specify the annual dialysis cost and the annual discount rate. You can also specify the currency label for labelling table columns (no currency conversion of any kind is performed).

Outputs

The calculation returns two outputs in the Shiny app:

• A table, which contains, for each treatment and slope (combinations of treatment and slope each form a row):
  • Time to dialysis (TTD) in years and the difference in TTD between treatments
  • Age at dialysis initiation
  • Time on dialysis
  • Costs and incremental costs for dialysis
• A figure, which shows eGFR trajectories for each treatment and user-specified eGFR value until the dialysis intiation threshold is reached.

CovalenceResearch/sloper-public documentation built on April 11, 2022, 12:02 a.m.