Is creatinine a better monitoring choice than cystatin C on survodutide?

Setup, so nobody has to ask: creatinine · cystatin C · survodutide.

I suspect the honest answer is that it depends, in which case I would like to know on what.

Assume I can obtain either option without difficulty, so availability is not the deciding factor.

What is the actual trade-off, and does it matter at the scale I am working at?

Answering this needs to distinguish screening from monitoring. A screening panel looks for the unexpected; a monitoring panel tracks something you already have a reason to watch.

A twenty-analyte panel run on a healthy person will produce, on average, one out-of-range result purely from how reference intervals are constructed. That is arithmetic rather than pathology.

Delta checks — comparing against your own previous value — are far more sensitive than comparing against a population interval, which is the argument for keeping a series rather than a snapshot.

External quality assurance schemes document between-laboratory differences on common analytes that routinely exceed the size of clinically interesting changes.

Keep the full report, not the number. You will need the units and the interval later.