24 Jan 2021
A newly published article critically appraises research and clinical methods for the diagnosis or screening of early DPN. In brief, functional measures are subjective and are difficult to implement due to technical complexity. Moreover, skin biopsy is invasive, expensive and lacks diagnostic laboratory capacity. Indeed, point-of-care nerve conduction tests are convenient and easy to implement however questions are raised regarding their suitability for use in screening due to the lack of small nerve fibre evaluation.
The signs and symptoms of DPN are insidious and current screening programmes rely on subjective tests of large nerve fibre dysfunction. NICE recommends vibration perception testing using a 128 Hz tuning fork together with a 10 g (Semmes-Weinstein) monofilament for the screening of DPN. However, these tests identify DPN at a late, irreversible, pre-ulcerative stage. Thus, an abnormal monofilament test is associated with a 3-year relative risk of 15% (95% CI 9.0 to 26.0) for foot ulceration or lower limb amputation. Despite, early and progressive injury to small fibres in diabetes, small nerve fibre assessment is not included in annual diabetic foot screening programmes.
‘Despite the higher sensitivity, the lower specificity of Neuropad compared to the 10 g monofilament and lower cost-effectiveness led NICE as part of the Medical Technologies Evaluation and Diagnostics Assessment Programme to not approve its use as a DPN screening test. We believe
this decision is short sighted as the specificity of any test which detects disease earlier is bound to be lower.’