Conventional smears versus liquid-based preparations for thyroid fine-needle aspirates: A systematic review and meta-analysis

Introduction: Thyroid fine-needle aspiration has traditionally been prepared using conventional smears (CS). Liquid-based preparations (LBP) have grown in popularity and yet, there is a lack of consensus about which method is superior. This review compared CS and LBP as an intervention in the management of thyroid nodules. Materials and methods: Medline, EMBASE, Scopus and ClinicalTrials.gov were searched to locate relevant studies. Observational studies comparing CS and LBP of consecutive thyroid fine-needle aspirations were included. Two reviewers independently screened, extracted, and entered data. Double data extraction included the following outcomes: (1) the proportion of inadequate smears and (2) the proportion of indeterminate smears. Studies were also assessed for risk of bias and heterogeneity. Results: From 599 unique studies, title/abstract screening identified 136 studies, and full text screening identified 13 studies. The 13 studies included 24,307 fine-needle aspirations from 19,433 patients and had high clinical, methodological, and statistical heterogeneity with low risk of bias. For CS and LBP, a meta-analysis of 12 studies showed no difference in the proportion of inadequate smears (risk difference: -0.00; 95% confidence interval [CI]: -0.04-0.04); 13 studies showed no difference in the proportion of indeterminate smears (risk difference: -0.02; 95% CI: -0.05-0.01). Sensitivity analysis of studies with low risk of bias had similar results. Conclusions: There is no difference between CS and LBP in the proportion of inadequate and indeterminate smears. Recommendations of one method over the other should be based on cost, feasibility, and accuracy, all of which require further study.