Can diabetic polyneuropathy and foot ulcers in patients with type 2 diabetes be accurately identified based on ICD-10 hospital diagnoses and drug prescriptions?

Abstract

Purpose: We examined whether diabetic polyneuropathy (DPN) and diabetic foot ulcers in type 2 diabetes can be accurately identified using International Classification of Diseases, 10th revision discharge diagnosis codes, surgery codes, and drug prescription codes. Methods: We identified all type 2 diabetes patients in the Central Denmark region, 2009-2016, who had ≥1 primary/secondary diagnosis code of "diabetes with neurological complication" (E10.4-E14.4), "diabetic polyneuropathy" (G63.2), or "polyneuropathy, unspecified" (G62.9). Patients with potential painful DPN and non-painful DPN were identified based on prescription history for serotonin-norepinephrine reuptake inhibitors, tricyclic antidepressants, or gabapentinoids. Likewise, type 2 diabetes patients with potential foot ulcers were identified based on diagnosis or surgery codes. We used medical record review as the reference standard and calculated positive predictive values (PPVs). Results: Of 53 randomly selected patients with potential painful DPN, 38 were classified as having DPN when validated against medical records; of these, 18 also had neuropathic pain, yielding a PPV of 72% (95% CI: 58-83%) for DPN and 34% (95% CI: 22-48%) for painful DPN. Likewise, among 54 randomly selected patients with potential non-painful DPN, 30 had DPN based on medical record data; of these, 27 had non-painful DPN, yielding PPVs of 56% (95% CI: 41-69%) and 50% (95% CI: 36-64%), respectively. Secondary E-chapter codes often denoted stroke or mononeuropathies, rather than DPN. Excluding secondary E-chapter codes from the algorithm increased the PPV for DPN to 78% (95% CI: 63-89%) for the painful DPN cohort and to 74% (95% CI: 56-87%) for the non-painful DPN cohort. Of 53 randomly selected patients with potential diabetic foot ulcer, only 18 diagnoses were confirmed; PPV=34% (95% CI: 22-48%). Conclusion: G-chapter and primary E-chapter diagnosis codes can detect type 2 diabetes patients with hospital-diagnosed DPN, and may be useful in epidemiological research. In contrast, our diabetic foot ulcer algorithm did not perform well.

Keywords: diabetic foot ulcer; diabetic polyneuropathy; epidemiology; positive predictive value; registries; type 2 diabetes.

Figure 1

Flowchart of study population. Overview of patient selection. ^aOf the 30,338 patients with potential non-painful DPN, 1826 later fulfilled the criteria for potential painful DPN. Thus, these patients are included in both the non-painful and painful DPN populations at two distinct time points. Likewise, after restricting to the Central Denmark region, 2009–2016. Abbreviation: DPN, diabetic polyneuropathy.