Table 1.

Proposed criteria to identify cases of CKDu

	Possible	Probable	Confirmed
CKD EPI eGFR < 60 ml/min/1.73m2 but higher threshold would be appropriate if younger subjects are included	X	X	X
Urine dipstick negative for protein, or no greater than 1+	X	X	X
Age 18–60 years with consideration of including adolescents in future studies	X	X	X
3-month repeat CKD EPI eGFR < 60 ml/min/1.73m2		X	X
Ultrasound demonstrating absence of cystic disease or large stone burden.			X
Renal biopsy showing primary tubulointerstitial disease			X
Diabetes: Diabetic subjects are not excluded (may coexist with CKDu). Studies of CKDu prevalence or incidence should be stratified by presence of diabetes
Location. If in a region where CKDu or a phenomenon akin to CKDu is suspected, the current approach could be used to estimate relative prevalence. Ideally a subset of patients should undergo biopsy to confirm, but that may be impossible in low resource settings.
Supportive features: Absence of edema; presence of hypokalemia and hyperuricemia. Ultrasound findings of loss of cortico-medullary differentiation or bilateral small kidney size.