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.