Ratio of varicella-zoster virus-specific immunoglobulin G antibody titre in the late acute phase to that in the early acute phase as a novel indicator of postherpetic neuralgia in patients with herpes zoster

Postherpetic neuralgia (PHN) is a common but feared complication of herpes zoster (HZ) caused by latent varicella-zoster virus (VZV) reactivation. Objectives: To investigate the relationship between the late-to-early acute phase VZV immunoglobulin (Ig)G antibody (Ab) titre ratio (VZV IgG L/E ratio) and pain intensity after 90 days from onset in patients with HZ. In this hospital-based retrospective cohort study, we analysed the data of patients who met the following criteria between July 2019 and September 2024: 1) those clinically diagnosed with HZ within seven days from onset; 2) those in whom VZV IgG Ab titres were measured twice in the early and late acute phases; and 3) those in whom pain intensity was assessed at the earliest time point after 90 days from onset, using the numerical rating scale (NRS). VZV IgG Ab titres were measured by enzyme-linked immunosorbent assay. A total of 21 patients were included in the analysis. The VZV IgG L/E ratio negatively correlated with NRS score after 90 days from onset (ρ= -0.53). When PHN was defined as pain associated with HZ (rated as 3 or more on the NRS), persisting or appearing for more than 90 days after the onset of HZ, the receiver operating characteristic curve analysis revealed a cut-off value of the VZV IgG L/E ratio for PHN to be 1.8, with 100% sensitivity and 93% specificity. Our results suggest that the VZV IgG L/E ratio could serve as a novel PHN indicator.

Abstract from PubMed