Study of serum vitamin D levels in patients with diabetic polyneuropathy using radioimmunoassay method.

Diabetic polyneuropathy (DPN) is a common and disabling complication of type 2 diabetes mellitus (T2DM). Vitamin D deficiency has been implicated as a potential modifiable risk factor. This study aimed to investigate the relationship between serum 25-hydroxyvitamin D [25(OH)D] levels and DPN using the radioimmunoassay (RIA) method. One hundred twenty T2DM patients (80 with DPN and 40 without neuropathy) have been enrolled, while 40 healthy volunteers served as group control. Neuropathy diagnosis was based on clinical assessment (through Michigan neuropathy screening instrument (MNSI) - both questionnaire and examination) and nerve conduction studies. Serum 25(OH)D levels were quantified using RIA. Vitamin D levels were significantly lower in DPN patients (mean 13.2ng/mL) compared to diabetic (18.3ng/mL) and healthy controls (31.2ng/mL, P<0.001). Vitamin D deficiency (<10ng/mL) was found in 72.5% of DPN patients. Apart from severe neuropathy, other factors (age, body mass index -BMI- and HbA1c) have all been mildly inversely correlated to Vitamin D levels. Vitamin D deficiency is significantly associated with the presence and severity of DPN. These findings support the clinical value of assessing and potentially improving vitamin D status in diabetic patients, particularly in those with severe neuropathy.