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SafetyGraphics / nepExplorer

Interactive Graphic for Exploring Kidney Function Data in Clinical Trials
https://safetygraphics.github.io/nepExplorer/
MIT License
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When calculating maximal value, should the x-axis measure determine the visit window? #40

Open samussiah opened 4 years ago

samussiah commented 4 years ago

i.e. should the visit window in which the maximal creatinine increase occurs be the same visit window from which to calculate eGFR decrease, or can the two measures be drawn from different visit windows depending on where the maximal change occurred?

samussiah commented 4 years ago

Related to #36

JimBuchanan commented 4 years ago

While there are a number of variables that go into the eGFR calculation, most of them do not change over the time interval we are assessing (e.g., age, sex, race, weight). The only variable that changes substantially over time, and drives the changes in eGFR, is serum creatinine. Thus, the window with the maximal creatinine increase should be the same window as the maximum eGFR decrease. But here's the catch. In reality, if we measured GFR with a better marker (like inulin), we would see "real" GFR decrease before creatinine started to increase. So when we calculate eGFR using a marker like cystatin C, we may see a maximal decrease in eGFR in a different window than that calculated based on serum creatinine. But from the standpoint of calculation, we can assume the same window for maximum creatinine increase and maximum eGFR (based on creatinine) and, separately, the same window for maximum cystatin C increase and maximum eGFR (based on cystatin C). Hope that helps.