The aim of this study was to try to determine the role of dry skin as a marker of decreased sudomotor function using a Neuropad® (Skyrocket Phytopharma [UK] Ltd), a visual indicator plaster method (IPM), as a risk factor for foot ulceration alongside accepted screening tools for neurological deficits in patients with Diabetes Mellitus. A total of 367 patients were enrolled, of which 308 completed the study, which was of six years duration 2012–2017. The exclusion criteria included medical, non-diabetes-related neuropathies, and dermatological conditions, etc, that were associated with skin dryness.
The neurological screening tests undertaken were the neuropathy symptom score (NSS) and neuropathy disability score (NDS). Additionally, vibration perception threshold (VPT) was evaluated in a subset of participants. Dryness of foot skin was assessed by an IPM, which was placed on non-callused skin over the plantar metatarsal head area bilaterally. If the applied IPMs changed colour from blue to pink this was considered ‘normal’, however, if at least one remained blue or patchy, it was deemed abnormal — autonomic dysfunction.
All subjects were instructed to attend the study clinic immediately if they suspected an ulcer. Follow-up visits occurred regularly every 3–6 months; non-attenders were contacted by phone and asked if they had any foot ulceration. Those who did not respond were withdrawn from the study. The mean age was 62.81 ± 11.28 years; there was an equal sex distribution gender male/female 153/155 with a mean diabetes duration of 11.5 years. Ulceration occurred in 55 patients, giving a 2.97% annual incidence of foot ulceration. Ulceration subjects were older (P=0.030), had longer diabetes duration (P=0.045), more often DPN (P<0.001), worse all neurologic modalities (P<0.05), had more retinopathy (P<0.001) and CAD (P=0.009).
Multivariate Cox-regression analysis after controlling for the age, gender, and DM duration demonstrated that the risk (hazard ratio, 95% confidence intervals) of DFU increased significantly with either abnormal IPM (3.319, 1.460–7.545, P=0.004) or high (≥6) NDS (2.782, 1.546–5.007, P=0.001) or high (≥25 volts) VPT (2.587, 1.277–5.242, P=0.008). ROC analysis showed that all neurological modalities could discriminate participants who developed DFU (P<0.001). IPM testing showed high sensitivity (0.86) and low specificity (0.49), while high versus low NDS and VPT showed low sensitivity (0.40 and 0.39, respectively) and high specificity (0.87 and 0.89, respectively) for identification of patients at risk for DFU.
The authors, therefore, conclude that IPM is a valid ulcer screening tool. However, this a small study; there are a few study design issues; there is no quantification of skin dryness, e.g. skin capacitance; and the NDS is prone to error especially regarding tendon reflexes. Furthermore, the exclusion criteria and IPM cost would restrict routine clinical use. This, however, is an interesting study and I would suggest a prospective study examining ulcer prevention in at-risk patients related to skin rehydration in xerosis. Please read the full paper and see what you think.
