Validity of medical record documented varicella-zoster virus among unvaccinated cohorts


Background: A varicella diagnosis or verification of disease history by any healthcare provider is currently accepted for determining evidence of immunity by the Advisory Committee on Immunization Practices (ACIP).
Objective: To examine the accuracy of medical record (MR) documented varicella history as a measure of varicella-zoster virus (VZV) immunity among unvaccinated individuals born after 1980. We also assessed methods to practically implement ACIP guidelines to verify varicella history using medical records.
Study Design: As part of a larger cross-sectional study conducted at three Philadelphia clinics from 2004–2006, we recruited 536 unvaccinated patients aged 5–19 y (birth years: 1985–2001). Varicella history was obtained from three sources: parent/patient interview, any MR documentation (sick and well visits) and MR documentation of a sick visit for varicella. All participants were tested for VZV IgG. For each source and three age groups (5–9, 10–14, 15–19 y old), positive predictive value (PPV) was calculated. Specificity of varicella history was compared between different sources using McNemar’s Chi-square.
Results: Among participants aged 5–9, 10–14 and 15–19 y the PPV for any MR documentation and sick visit diagnosis were 96% and 100%, 92% and 97%, and 99% and 100%, respectively. The specificity for sick visit documentation was higher than any MR documentation and patient/parent recall among all age groups; however, these differences were only statistically significant when comparing sick visit documentation to parent/patient recall for 10-14 y olds.
Conclusion: Sick visit documentation of varicella in the MR is an accurate predictor of varicella seropositivity and useful for confirming disease history among unvaccinated persons (birth years: 1985–2001). This method is a practical way to verify varicella history using the ACIP guidelines.

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Validity of medical record documented varicella-zoster virus among unvaccinated cohorts