Immunoreactivity of TTF‐1, GATA‐3, CEA, and p16/Ki67 cocktail in Cellprep®‐processed control samples: Comparison of long‐term storage in vials and slides

Cellprep® (CP) is a novel liquid-based cytology (LBC) system. This study aimed to assess the immunoreactivity of control samples stored long-term under two storage conditions using CP.The immunoreactivity in control samples was evaluated under two sample storage conditions: CP vial storage at room temperature (RT: 20-25°C) and CP slide storage in a refrigerator (2-6°C). Clinical samples as controls (total: positive/negative) were immunostained using thyroid transcription factor-1 (TTF-1) (20: 14/6), GATA binding protein 3 (GATA-3) (13: 10/3), carcinoembryonic antigen (CEA) (23: 15/8), and the p16/Ki67 cocktail (20: 12/8) markers. The first immunocytochemistry (ICC) was performed within 1 month using CP vials stored at RT. Samples stored in CP vials and on CP slides were used for the second (within 3-6 months) and third (within 6-11 months) ICCs. Compared with the first ICC, the concordance of immunoreactivity for the second and third ICCs was evaluated using the weighted kappa coefficient.For TTF-1, CEA, and the p16/Ki67 cocktail markers, ICC controls had stable immunoreactivity for a minimum of 6 months when samples were stored in CP vials (kappa coefficients >0.8), whereas for GATA-3, they were for 3 months. On CP slides, only for the p16/Ki67 cocktail, ICC controls had stable immunoreactivity for at least 3 months (kappa coefficient >0.8).Clinical samples as ICC controls revealed consistently more stable immunoreactivity in CP vials than on CP slides for TTF-1, GATA-3, CEA, and the p16/Ki67 cocktail markers.