Current issues of ACP Journal Club are published in Annals of Internal Medicine


Prognosis

Postherpetic neuralgia was not frequent or severe after a first episode of herpes zoster

PDF

ACP J Club. 2001 Mar-Apr;134:70. doi:10.7326/ACPJC-2001-134-2-070


Source Citation

Helgason S, Petursson G, Gudmundsson S, Sigurdsson JA. Prevalence of postherpetic neuralgia after a first episode of herpes zoster: prospective study with long term follow up. BMJ. 2000 Sep 30; 321:794-6. [PubMed ID: 11009518] (All 2001 articles were reviewed for relevancy, and abstracts were last revised in 2007.)


Abstract

Question

In patients with a first episode of herpes zoster, what is the clinical course of the disease and the duration of pain?

Design

Inception cohort followed for 12 months.

Setting

Catchment area of 100 000 people for 62 general practitioners in Iceland.

Patients

421 patients {mean age 42 y, 56% women}* who had a first episode of herpes zoster. Patients with a history of zoster were excluded. Follow-up was complete at 1 year.

Assessment of prognostic factors

Sex and age.

Main outcome measures

Severity and duration of pain and prevalence of postherpetic neuralgia.

Main results

Sex was not a predictor of postherpetic neuralgia at any point during follow-up. Age was a predictor of pain severity and duration. The odds ratio for pain per 10 years of age difference was 1.87 (95% CI 1.56 to 2.23) after 1 month, 2.11 (CI 1.56 to 2.84) after 3 months, and 2.33 (CI 1.48 to 3.69) after 12 months. In patients < 60 years of age, the prevalence of postherpetic neuralgia was low, and no patients had more than mild pain after 3 months (5 patients [1.8%] after 3 mo; 2 patients [0.7%] after 12 mo). In patients ≥ 60 years of age, the frequency and severity of neuralgia increased. After 3 months, 23 patients (20%) had pain, and 2 patients (1.7%) had severe pain. After 12 months, 12 patients (9.4%) had pain, but none had severe pain. None of a random sample of 183 patients who were free of neuralgia at 12 months reported any recurrence of pain during long-term follow-up (3.2 to 7.0 y). Among 14 patients (all ages) who reported pain after 12 months, 12 considered the pain mild.

Conclusions

In patients with a first episode of herpes zoster, the course of disease was benign among those < 60 years of age. In older patients, the frequency of neuralgia increased, but pain severity was rarely more than mild. Patients free of pain had no pain recurrence.

*Information provided by author.

Sources of funding: In part, Icelandic College of Family Physicians and Research Fund of the University of Iceland.

For correspondence: Dr. S. Helgason, Arbaer Health Care Centre, IS-110 Reykjavik, Iceland. E-mail: sh@centrum.is.


Commentary

The community-based, prospective study by Helgason and colleagues of 421 patients with a first episode of herpes zoster found that the point prevalence of postherpetic neuralgia after 1 month was only 19%, after 3 months was 7%, after 1 year was 3%, and after 3 years was about 1%. These results are consistent with previous community-based studies (1) but are lower than the 3-month point prevalence estimates of 33% to 43% observed among patients enrolled in trials of antiviral agents who were allocated to placebo (2).

The higher prevalence of postherpetic neuralgia in clinical trials is mainly caused by selection bias; severe cases of postherpetic neuralgia (e.g., older patients with severe pain and rash) are more likely to be referred to a hospital and enrolled in trials. In the study by Helgason and colleagues, the prevalence of postherpetic neuralgia at 3 months among patients > 60 years of age (20%) was similar to that observed among 181 patients of the same age in the placebo arm of a clinical trial (24%) (3).

Although individual trials suggest that antiviral drugs (famciclovir and valaciclovir) reduce the prevalence of postherpetic neuralgia by as much as 50%, a recent meta-analysis suggests a more conservative treatment effect (2).

If antiviral therapy reduces postherpetic neuralgia by 25% (which needs to be confirmed), then treating all 421 patients in Helgason and colleagues' study would have reduced postherpetic neuralgia at 1 month from 19% to 14.25% (absolute risk reduction [ARR] 4.75%, n = 20, number needed to treat [NNT] = 21); at 3 months, from 7% to 5.25% (ARR = 1.75%, n = 7, NNT = 57); and at 1 year, from 3% to 2.25% (ARR = 0.75%, n = 32, NNT = 133). Restricting antiviral therapy to the 115 patients > 60 years of age would reduce postherpetic neuralgia at 3 months from 20% to 15% (ARR = 5%, n = 6, NNT = 20), saving 6 patients from postherpetic neuralgia at 3 months compared with 7 patients if all patients were treated.

This study highlights that herpes zoster is benign for most patients and that treatment of all patients with antiviral therapy is unnecessary. Further research is needed to identify more precisely the few patients who will have severe postherpetic neuralgia and whether antiviral therapy really is effective for them (and if so, how effective and with which agent, what dose, and for how long).

Graeme J. Hankey, MBBS
Royal Perth Hospital
Perth, Western Australia, Australia


References

1. Choo PW, Galil K, Donahue JG, et al. Risk factors for postherpetic neuralgia. Arch Intern Med. 1997;157:1217-24. [PubMed ID: 9183233]

2. Wood MJ, Kay R, Dworkin RH, Soong SJ, Whitley RJ. Oral acyclovir therapy accelerates pain resolution in patients with herpes zoster: a meta-analysis of placebo-controlled trials. Clin Infect Dis. 1996;22:341-7. [PubMed ID: 8838194]

3. McKendrick MW, McGill JI, Wood MJ. Lack of effect of acyclovir on postherpetic neuralgia. BMJ. 1989;298:431. [PubMed ID: 2495051]