Assessment of Serum Vitamin D Levels in the serum of Patients with Postherpetic neuralgia and its correlation to pain severity: A cross‐sectional comparative study

Introduction Vitamin D is an essential micronutrient for the maintenance of many functions in the human body. Postherpetic neuralgia (PHN) is caused by the reactivation of the latent varicella‐zoster virus (VZV) in the neurons. This study aims to assess the serum vitamin D level in patients with PHN and to correlate the level of vitamin D with pain severity. Methods and materials A hospital‐based cross‐sectional comparative study was conducted in the period from April 2019 to January 2021. One hundred and sixty‐two individuals, matched for age and gender, divided into cases and controls (81 for each). Serum levels of 25(OH)D were measured for cases and controls. Demographic data were taken, and then the diagnosis of neuropathic pain in cases was established using the Douleur Neuropathique 4 (DN4) questionnaire. Results We included 39 (52%) males in the PHN group and 36 (48%) in the control group. There was no significant difference between groups regarding age, marital status, smoking and BMI. The duration of pain in our study had a mean of 7.6 ± 3.6 months. We found the DN4 score for the pain to be negatively associated with vitamin D levels (Pearson's correlation coefficient: −0.511, P = .000). The levels of vitamin D were moderately associated with pain duration (Pearson's correlation: −0.466, P = .000). Conclusion PHN patients had a high prevalence of vitamin D deficiency and those who had vitamin D deficiency were older and had higher degrees of pain for a longer duration. In PHN patients, vitamin D deficiency was moderately associated with increased severity and duration of pain.