['This was a pilot study to establish a protein difference between thyroglossal duct cyst fluid relative to oral saliva, in order to differentiate patients with residual thyroglossal cyst from those with salivary fistula in the case of post-Sistrunk procedure incisional drainage. Past immunohistochemistry studies on archived tissue blocks from post-Sistrunk procedure patients have shown MUC5AC to have elevated concentrations in thyroglossal duct relative to salivary tissue; secretory immunoglobulin A (IgA) was also chosen as a candidate protein based on previously published reports of its increased concentration in saliva relative to respiratory secretions.', 'Diagnostic tests were assessed. Thyroglossal duct cyst fluid and oral saliva were obtained from 12 patients. Enzyme-linked immunosorbent assay (ELISA) was then performed on the samples to identify the presence of MUC5AC and IgA.', 'Tertiary care hospital.', 'Patient fluid samples were taken immediately postoperatively for patients undergoing Sistrunk procedure at one institution. Presence of thyroglossal duct cyst was confirmed in all cases by pathology.', 'Seven of 12 thyroglossal duct cyst fluid samples were shown to have elevated absorbance with ELISA for MUC5AC. In experiments for IgA, 10 of the 12 saliva samples had elevated absorbance compared with thyroglossal duct fluid samples obtained from the same patient.'] Does immunoglobulin A define secretions from salivary tissue in post-Sistrunk procedure drainage?