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BACKGROUND: The test-negative design is a variant of the case-control study being increasingly used to study influenza vaccine effectiveness (VE). In these studies, patients with influenza-like illness are tested for influenza. Vaccine coverage is compared between those testing positive versus those testing negative to estimate VE. OBJECTIVES: We reviewed features in the design, analysis and reporting of 85 published test-negative studies. DATA SOURCES: Studies were identified from PubMed, reference lists and email updates. Study eligibility: All studies using the test-negative design reporting end-of-season estimates were included. STUDY APPRAISAL: Design features that may affect the validity and comparability of reported estimates were reviewed, including setting, study period, source population, case definition, exposure and outcome ascertainment and statistical model. RESULTS: There was considerable variation in the analytic approach, with 68 unique statistical models identified among the studies. CONCLUSION: Harmonization of analytic approaches may improve the potential for pooling VE estimates.
Sullivan et al. (Tue,) studied this question.