Association of patient-rated severity with other outcomes in patients with painful diabetic peripheral neuropathy

OBJECTIVE To evaluate the association of patient-reported severity of painful diabetic peripheral neuropathy (pDPN) with other outcomes in a European population of patients using the Adelphi Disease Specific Programme for pDPN (DSP III, 2008). METHODS The severity of patients' pDPN (mild, moderate, or severe) was rated independently by both patients and physicians. Relationships were evaluated between patient-reported pDPN severity and other patient-reported outcomes including pain, sleep, function, and work productivity. Physicians rated the severity of patients' pDPN (1 = mild, 2 = moderate, 3 = severe) and sleep interference. RESULTS Patient-reported data were available from 634 individuals (56.2% male, mean age 63 years) from France, Germany, Italy, and the UK, of whom only 22.2% reported that they were currently employed. pDPN severity was rated as mild, moderate, and severe by 22.2%, 60.9%, and 16.9% of the patients, respectively. There was a significant association between patient-rated and physician-rated pDPN severity (P < 0.0001), although there were discrepancies in agreement (kappa = 0.37, 95% confidence interval [CI] 0.31, 0.43; weighted kappa = 0.43, 95% CI 0.37, 0.48) among physician and patient ratings in a substantial proportion of patients across severity categories. Higher pDPN severity was associated with greater interference of daily function including sleep (P < 0.0001 for all pairwise comparisons). Among employed patients, percent of pDPN-related impairment while at work (presenteeism) and overall work impairment increased with greater pDPN severity, resulting in indirect costs that increased significantly with pDPN severity; $8266, $15,449, and $24,300 for mild, moderate, and severe pDPN, respectively (overall P < 0.001). CONCLUSION Severity of patient-rated pDPN was significantly associated with outcomes, including function and productivity; poorer function and lower productivity were reported at higher pDPN severity levels. Moreover, physicians rated pDPN severity different from patients in a substantial proportion of patients.