“Choosing “No” will calculate an indexed eGFR value, standardized to a body surface area of 1.73m2 (units: mL/min/1.73m2)
Assessment for CKD staging and CKD progression should generally be assessed using the indexed eGFR value.”
The way I read #6 in the FAQs, we have to index to body size to properly compute kidney disease.
https://www.kidney.org/sites/default/files/441-8491_2202_faqs_aboutgfr_v5.pdf