Limitations of our study are the existence of coding errors and the possible misclassification of the herpes zoster diagnosis in the National Registry of Patients.
Despite efforts to improve capture of herpes zoster ophthalmicus by looking for acute eye diseases or specific therapy within 2 weeks of zoster and specified nonacute eye diseases within 3 months of zoster, some misclassification of herpes zoster ophthalmicus is likely [ 31].
10 11 34 35 We found some evidence that type 1, but not type 2, diabetes was associated with an increased risk of zoster (although differentiating between type was not based on diagnostic codes, so misclassification is possible).
When the rash is absent (early or late in the disease, or in the case of zoster sine herpete), herpes zoster can be difficult to diagnose.
We identified a total of 145 397 incident cases of zoster.
As the zoster vaccine is expensive, targeting vaccination towards groups at high risk of zoster is necessary.
Herpes zoster ophthalmicus was identified from the presence of specific diagnostic codes, or, when the zoster codes were nonspecific, from diagnoses of or treatments for acute eye infection within 2 weeks of zoster onset or from records of first-ever specific nonacute eye conditions known to be associated with zoster (eg, conjunctival scarring or episcleritis), within 3 months after zoster onset.
Cases in the Clinical Practice Research Datalink were those with a zoster Read code and at least 12 months' follow-up before a first diagnosis of zoster, to exclude past cases of zoster recorded retrospectively after registration at a general practice.
Validation of zoster diagnoses in primary care in the Netherlands found that 90.8% of cases had raised antibodies indicating recent zoster infection, suggesting that diagnosis of zoster has a high positive predictive value.
