TABLE 1.

Criteria for a valid surrogate endpoint, applied to potential surrogate endpoints in kidney transplantation.

Criterion	Proteinuria	DSA	eGFR + proteinuria combined	Chronic graft histology	iBox score
Disease process (graft failure) sufficiently understood	Confirmed	Confirmed	Confirmed	Confirmed	Confirmed
Biologic plausibility	Confirmed	Confirmed	Confirmed	Confirmed	Confirmed
Strength of consistency supporting relationship between surrogate marker and outcome	Confirmed	Confirmed	Not confirmed	Not confirmed	Confirmed
Treatment effects on surrogate endpoint predict treatment effects on clinical outcome of interest	Not confirmed	Not confirmed	Not confirmed	Not confirmed	Not confirmed

DSA, donor-specific antibody; eGFR, estimated glomerular filtration rate.