Diagnostic cohort studies that compared fine-needle aspiration cytology with the reference standard of histology and which reported raw data (numbers of true positives, false negatives, false positives and true negatives) for the diagnosis of head and neck masses were eligible for inclusion. Where data were not fully reported, authors were contacted and requested to provide further information. Studies of skin tumors, children, guided-image studies and studies of the complications of fine-needle aspiration cytology were excluded.
The titles of retrieved studies were screened to remove obviously irrelevant articles and full papers. The remaining studies were graded for level of evidence. The authors did not state how many reviewers were involved in this process.