Incidence of diabetic peripheral neuropathic pain in primary care – a retrospective cohort study using the United Kingdom General Practice Research Database

Catherine Reed,¹ Jihyung Hong,² Diego Novick,¹ Alan Lenox-Smith,³ Michael Happich<sup>4

1</sup>Global Health Outcomes, Eli Lilly and Company, Windlesham, Surrey, UK; ²Personal Social Services Research Unit, London School of Economics and Political Science, London, UK; ³Eli Lilly UK, Basingstoke, UK; ⁴Eli Lilly and Company, Bad Homburg, Germany

Purpose: To determine the incidence of diabetic peripheral neuropathic pain (DPNP) in the United Kingdom (UK) primary care population using the General Practice Research Database (GPRD).
Patients and methods: This retrospective cohort study identified incident cases of DPNP in the UK GPRD between July 1, 2002 and June 30, 2011, using diagnostic codes. Trends in the incidence rate were examined by dividing the study period into 3-year periods: (1) July 1, 2002–June 30, 2005; (2) July 1, 2005–June 30, 2008; and (3) July 1, 2008–June 30, 2011. Patient characteristics (age, sex, comorbidities) and initial pharmacological treatment were described; the proportion of patients with incident DPNP, who had previously been screened for neuropathic symptoms, was determined.
Results: Among almost 7.5 million persons contributing 38,118,838 person-years of observations in the GPRD, 6,779 new cases of DPNP were identified (45.5%, women), giving an incidence rate of 17.8 per 100,000 person-years (95% confidence interval [CI] 17.4–18.2). The incidence of DPNP increased with age, but it was stable over the three consecutive 3-year periods: 17.9, 17.2, and 18.4 cases per 100,000 person-years. Of the 6,779 patients with incident DPNP, 15.5% had prior neuropathic screening during the study period. The majority of patients with incident DPNP (84.5%) had a treatment for pain initiated within 28 days of first diagnosis. The most common first-line treatments prescribed were tricyclic antidepressants (27.2%), anticonvulsants (17.0%), and nonsteroidal anti-inflammatory drugs (14.9%), with 26.6% of patients receiving combination therapy as their initial treatment.
Conclusion: The incidence of DPNP in UK primary care has remained steady over the past 10 years. Our results suggest that DPNP is underdiagnosed, and initial treatment prescribed does not follow clinical guidelines.

Keywords: diabetes, peripheral neuropathy, pain, incidence, primary care