Predictors of pain intensity and persistence in a prospective Italian cohort of patients with herpes zoster: relevance of smoking, trauma and antiviral therapy

BACKGROUND: Herpes zoster (HZ) is a common disease, characterized by rash-associated localized pain. Its main complication, post-herpetic neuralgia (PHN), is difficult to treat and may last for months to years in the wake of rash resolution. Uncertainties remain as to the knowledge of predictors of HZ-related pain, including the role of antiviral therapy in preventing PHN in ordinary clinical practice. This prospective cohort study was aimed at investigating pain intensity at HZ presentation and its correlates, as well as the incidence of PHN and its predictors. METHODS: Patients diagnosed with HZ were consecutively enrolled by a network of Italian General Practitioners and Hospital Units in the health district of Pescara, Italy, over two years. Uncertain cases were referred for microbiological investigation. Data were collected through electronic case report form (e-CRFs) at enrolment and at 1, 3, 6 and 12 months after enrolment. Pain intensity was coded on a five-degree semi-quantitative scale at each time point. PHN was defined as pain of any intensity during follow-up and quantified using an area-under-the-curve (AUC) method. RESULTS: Four hundred and forty-one patients composed the final sample. Mean age was 58.1 years (SD = 20.4 years); 43.5% of patients were males; 7.9% did not receive prescription of antivirals. Intense/very intense pain at presentation was reported by 25.2% of patients and was significantly associated with female gender, older age, cigarette smoking, trauma and/or surgery at HZ site (logistic regression). PHN was diagnosed in 51.2% of patients at one month and in 30.0% of patients at three months. PHN was significantly associated with pain intensity at presentation, age, smoking, trauma and missed antiviral prescription (generalized estimating equations model). The same factors were also independent predictors of the overall pain burden as described by the AUC method (linear regression). CONCLUSIONS: Smoking, traumas and surgery at the HZ site emerged as new predictors of both HZ-related pain intensity and persistence, opening new perspectives in the prevention of HZ-related pain. An independent line of evidence was provided for the efficacy of antiviral therapy in preventing PHN and reducing total pain burden.