The development and validation of the Norfolk QOL-DN, a new measure of patients' perception of the effects of diabetes and diabetic neuropathy.

BACKGROUND: This study was designed to develop and validate a patient-reported outcomes measure, sensitive to the different features of diabetic neuropathy (DN)-small fiber, large fiber, and autonomic nerve function. METHODS: The review of 1,000 structured patient interviews guided the development of 28 items pertaining specifically to the symptoms and impact of large fiber, small fiber, and autonomic nerve function. These items, in addition to 14 generic health status items and five general information items formed the 47-item Norfolk Quality of Life Questionnaire-Diabetic Neuropathy (QOL-DN). Items were grouped according to small fiber, large fiber, and autonomic nerve function, symptoms, and activities of daily living (ADL). Scores in individual domains were aggregated to provide a total score. Item groupings were tested for their ability to distinguish between the effects of specific nerve fiber deficits in 262 subjects-81 healthy controls (C), 86 controls with diabetes (DC), and 95 patients with DN-using one-way analysis of variance (ANOVA). Internal consistency was estimated using Cronbach's alpha coefficient. Test-retest reliability over a 4-6-week period was estimated by intra-class correlation coefficients and ANOVA on data of a subset of patients and controls. RESULTS: Differences between DN subjects and both DC and C subjects were significant (P < 0.05) for all item groupings. Total quality of life (QOL) scores correlated with total neuropathy scores. The ADL, total QOL, and autonomic scores were greater in DC than C subjects (P < 0.05). Intra-class correlation coefficients were > 0.9 for most domains. Internal consistency of the fiberspecific domains using Cronbach's alpha was > 0.6 and up to 0.8. CONCLUSIONS: The fiber-specific domains of the QOL-DN demonstrated acceptable reliability and ability to discriminate between subjects with and without neuropathy. Not surprisingly, the DN group scored significantly (P < 0.05) higher than either of the two control groups (i.e., greater impairment). The positive scores for the DC group in the ADL and autonomic domains suggest that diabetes per se impacts these aspects of QOL.

German-translated Norfolk quality of life (QOL-DN) identifies the same factors as the English version of the tool and discriminates different levels of neuropathy severity.

BACKGROUND: The development and validation of Norfolk QOL-DN, a fiber-specific, quality-of-life tool for diabetic neuropathy, was published previously (Part 1). This study (Part 2) defines the psychometric properties of the German-translated Norfolk QOL-DN in a large multicenter (96 sites) population with neuropathy ranging from minimal to severe, comparing them with those in the original English/American version in a 30-center European/North American population with mild neuropathy; determines the power of the German-translated version in a five-staged diabetic peripheral neuropathy (DPN) German population to discriminate different levels of neuropathy severity; and establishes factors having the greatest impact on QOL. METHODS: One hundred eighty-six German patients were assessed: asymptomatic of DPN (n = 40), symptomatic (n = 46), DN with foot-ulcer history (n = 32), DN with amputations (n = 22), and DN amputation history (n = 46). German-translated Norfolk QOL-DN was administered to 177 patients with staged DN complications. German-translated Norfolk QOL-DN data were compared with QOL-DN data from the European/American study of 379 mild neuropathy patients. Exploratory factor analysis assessed factor structure consistency in the translated instrument. Ordinal regression analysis (polytomous universal model) was used to evaluate the association between factor scores and complication stages. RESULTS: The German translation identified the same five factors in more advanced neuropathy as in the English mild neuropathy population. Total QOL scores differed among each of the five neuropathy severity groups [analysis of variance p < 0.001, Tukey-Kramer post hoc, alpha = 0.05]. Two factors emerged as predictors of impaired QOL and disease severity: physical function/large fiber (Wald chi(2) = 6.188, p = 0.013) and activities of daily living (ADL)(Wald chi(2) = 9.098, p = 0.003). CONCLUSIONS: Norfolk QOL-DN discriminates levels of neuropathy within and between populations. Physical functioning and ADL are the most important determinants of QOL. Early occurrence of orthostasis suggests a redefinition of autonomic neuropathy to be more symptom inclusive.