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Quantifying the incidence and burden of herpes zoster in New Zealand general practice: a retrospective cohort study using a natural language processing software inference algorithm
  1. Nikki M Turner1,
  2. Jayden MacRae2,
  3. Mary L Nowlan1,
  4. Lynn McBain3,
  5. Maria H Stubbe3,
  6. Anthony Dowell3
  1. 1 Department of General Practice and Primary Health Care, University of Auckland, Auckland, New Zealand
  2. 2 DataCraft Analytics Limited, Wellington, New Zealand
  3. 3 Department of Primary Health Care and General Practice, University of Otago, Wellington, New Zealand
  1. Correspondence to Dr Nikki M Turner; n.turner{at}


Objective To investigate the incidence of primary care presentations for herpes zoster (zoster) in a representative New Zealand population and to evaluate the utilisation of primary healthcare services following zoster diagnosis.

Design A cross-sectional retrospective cohort study used a natural language processing software inference algorithm to identify general practice consultations for zoster by interrogating 22 million electronic medical record (EMR) transactions routinely recorded from January 2005 to December 2015. Data linking enabled analysis of the demographics of each case. The frequency of doctor visits was assessed prior to and after the first consultation diagnosing zoster to determine health service utilisation.

Setting General practice, using EMRs from two primary health organisations located in the lower North Island, New Zealand.

Participants Thirty-nine general practices consented interrogation of their EMRs to access deidentified records for all enrolled patients. Out-of-hours and practice nurse consultations were excluded.

Main outcome measures The incidence of first and repeated zoster-related visits to the doctor across all age groups and associated patient demographics. To determine whether zoster affects workload in general practice.

Results Overall, for 6 189 019 doctor consultations, the incidence of zoster was 48.6 per 10 000 patient-years (95% CI 47.6 to 49.6). Incidence increased from the age of 50 years to a peak rate of 128 per 10 000 in the age group of 80–90 years and was significantly higher in females than males (p<0.001). Over this 11-year period, incidence increased gradually, notably in those aged 80–85 years. Only 19% of patients had one or more follow-up zoster consultations within 12 months of a zoster index consultation. The frequency of consultations, for any reason, did not change between periods before and after the diagnosis.

Conclusions Zoster consultations in general practice are rare, and the burden of these cases on overall general practice caseload is low.

  • herpes zoster
  • primary care
  • virology
  • health informatics

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  • Contributors NMT, MLN and AD conceived the study. MHS and MLN managed the ethical approval and consent processes. AD, LMB and NMT provided clinical input into the algorithm design. JMR designed and built the natural language processing tools, programmed and trained the algorithm, and conducted the data analyses. AD and LMB classified the consultation records in the gold standard sets. NMT and MLN were the principal writers of the manuscript. All authors reviewed and revised the manuscript and approved its final version. All authors had full access to all of the data in the study and can take responsibility for the integrity of the data and accuracy of the analysis. All authors contributed to the development of the overall study methodology.

  • Funding This work was supported by a New Zealand Lottery Health Research grant.

  • Disclaimer The funding body had no role in the collection or analysis of data or preparation of the manuscript.

  • Competing interests None declared.

  • Patient consent Not required.

  • Ethics approval This study was approved by the University of Auckland Human Participants Ethics Committee Ref. 017617 on 25 July 2016.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement No additional data are available.

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