Table 1.

Outcome variables.

Category	ICD codes	OPS codes
“mild to moderate CKD”	N18.1, N18.2, N18.3, N18.81, N18.82, N18.83
“severe CKD”	N18.0, N18.4, N18.5, N18.84, Z49.1, Z49.2, Z94.0, Z99.2	5-555, 8-853, 8-854, 8-855, 8-857
“general CKD”	N19, N18.8, N18.80, N18.9, N18.1, N18.2, N18.3, N18.81, N18.82, N18.83, N18.0, N18.4, N18.5, N18.84, Z49.1, Z49.2, Z94.0, Z99.2	5-555, 8-853, 8-854, 8-855, 8-857

Change of ICD code N18.- in 2010; both versions of ICD coding for CKD (before and after 2010) were used for the analyses.