Comparison of Liqui--PREP™ and conventional preparations in thyroid fine needle aspiration

Background : Liqui-PREP™ (LP) is a new liquid-based cytologic preparation that produces a thin layer of cells. Methods : Thyroid aspirates were obtained from 189 patients and divided to prepare pairs of conventional preparation (CP) and LP slides. The CP slides were routinely diagnosed by attending staffs and classified into the six categories. LP slides were independently evaluated by three cytopathologists and classified in an identical manner. Agreements between CP and LP diagnoses were investigated and interobserver variability of thyroid aspiration cytology results obtained using the LP method was determined using kappa values. Results : CP and LP slides from 155 patients (83%) were identically classified by all of three cytopathologists. Concurrences between CP and LP diagnoses for the three cytopathologists were 89% (κ=0.78), 92% (κ=0.87), and 85% (κ=0.70), respectively. Interobserver agreement among the three cytopathologists for LP slides ranged from substantial to almost perfect (κ=0.84, 0.74 and 0.84). However, a lack of interobserver agreement was found for LP slides of the undetermined category as determined by original CP-based diagnoses. Moreover, cytomorphological alterations in the benign category appeared more worrisome for LP slides. Conclusions : An awareness of the novel cytomorphologic changes induced by the LP method is needed to avoid misinterpretations.