Table 1.

Algorithms of in- and outpatient discharge codes and prescription codes used to identify patients with painful and non-painful DPN and diabetic foot ulcer

Type 2 diabetesa

≥1 diabetes discharge code (E10-E14, H36.6, O24 [except O24.4], G63.2)

OR

≥1 prescription of a glucose-lowering drug (ATC: A10)b

Potential DPN:

Type 2 diabetes plus ≥1 discharge code for “diabetes with neurological complication” (E10.4, E11.4, E12.4, E13.4, E14.4)c

OR

Type 2 diabetes plus ≥1 discharge code for “diabetic polyneuropathy” (G63.2)

OR

Type 2 diabetes plus ≥1 discharge code for “polyneuropathy, unspecified” (G62.9)

Potential painful DPN:

DPN plus ≥1 prescription code for antiepileptic drugs minus an epilepsy discharge code (G40+G41)

OR

DPN plus ≥1 prescription code for antidepressants (SNRI/TCA) minus a depression/anxiety discharge code (F30-F34, F40-42, F48.8+F48.9)

Potential non-painful DPN:

DPN patients that do not fulfil the criteria for painful DPN

Potential diabetic foot ulcer:

Type 2 diabetes plus ≥1 discharge code for “diabetes with peripheral vascular complication” (E10.5, E11.5, E12.5, E13.5, E14.5)

OR

Type 2 diabetes plus ≥1 discharge code for “ulcer” (L97, L98.4, R02)

OR

Type 2 diabetes plus ≥1 discharge code for “osteomyelitis” (M86)

OR

Type 2 diabetes plus ≥1 surgery code for surgery of lower extremity (KQDA, KQDB, KQDG)

Notes: ^aAll patients younger than 30 years at diagnosis treated with insulin monotherapy were excluded in order to minimize misclassification of type 1 diabetes patients. ^bExcept females aged 20–39 prescribed metformin exclusively in order to minimize misclassification of patients with polycystic ovarian syndrome. ^cExcluding patients with ICD-10 codes for G73.0 amyotrophy, G99.0 autonomic neuropathy, G59.0 mononeuropathy.

Abbreviations: DPN, diabetic polyneuropathy; ICD-10, International Classification of Diseases; version 10; SNRI, serotonin–noradrenalin reuptake inhibitors; TCA, tricyclic antidepressants.