Serum interleukin‐10 level increases in patients with severe signs or symptoms of herpes zoster and predicts the duration of neuralgia

Herpes zoster (HZ) is caused by reactivation of latent varicella zoster virus (VZV) in the cranial nerve or dorsal root ganglia, with spread of the virus along the sensory nerve to the dermatome. Postherpetic neuralgia is a feared complication of HZ and impairs patients' quality of life enormously. However, there is no predictor of the duration of neuralgia. Our objective was to investigate whether there are correlations between the duration of neuralgia and serum levels of potential biomarkers in order to find practical predictors of the duration of neuralgia. Patients who were diagnosed with HZ at our hospital from April 2013 to January 2014 were included in this study. Serum levels of cytokines and other biomarkers were measured using commercial enzyme-linked immunosorbent assay kits. Thirty patients (15 men and 15 women) with HZ were enrolled in this study. The mean age was 66.1 ± 9.2 (standard deviation) years (range, 51-84 years). Four patients were evaluated as having mild, 19 as having moderate, and seven as having severe HZ. Patients with severe HZ suffered from neuralgia for a significantly longer period of time than patients with mild-to-moderate HZ (9.86 ± 8.25 months vs. 2.01 ± 2.68 months, severe vs. mild-to-moderate, p = 0.0021). The serum interleukin (IL)-10 level was significantly higher in patients with severe HZ than in those with mild-to-moderate HZ (12.93 ± 3.27 pg/mL vs. 6.74 ± 3.72 pg/mL; severe vs. mild-to-moderate; p = 0.0487). Furthermore, the serum IL-10 level was significantly correlated with the duration of neuralgia (r = 0.5193, p = 0.0111). Lastly, the serum IL-10 level significantly decreased after treatment in comparison with that before treatment (from 8.15 ± 4.46 pg/mL to 4.32 ± 11.83 pg/mL, p < 0.0001). In conclusion, these results suggest that the serum IL-10 level is an objective biomarker of the severity of HZ, and that the serum IL-10 level can be a practical predictor of the duration of neuralgia.