Table 1.

Comparison of fixation and preparation of cytological cell blocks and routine PD-L1 staining for NSCLC for the 2 involved pathology departments (for further details, see online suppl. material)

Issue	Lund	Halmstad
Cell block preparation of pleural effusions	Washed 1–2 times in CytoLyt®, then PreservCyt® 1–3 days, then Cellient™ cell block	Formalin fixation of centrifuged pellet in cassette (bloody samples first washed ≤3 times in CytoLyt®)
Cell block preparation of other cytology	CytoLyt® a few hours, then PreservCyt® 1–3 days, then CellientTM cell block	CytoLyt® 1–24 h, then formalin fixation of centrifuged pellet in cassette (nodal EBUS aspirations first in sodium chloride for less than a few hours)
PD-L1 staining	22C3 (Agilent/pharmDx)	28–8 (Agilent/pharmDx)
Staining platform	Ventana Benchmark Ultra	Dako Autostainer Link 48
Control tissue	Tonsil and placenta (on each slide)	Tonsil, placenta, and either small intestine or appendix (on each slide); separate slide stained with negative control reagent; positive and negative cell lines (in each run)
PD-L1 analysis of small specimens	Always performed, biopsy preferred in the clinical setting (parallel staining of cell blocks common in 2017–2019)	Always performed, biopsy preferred in the clinical setting
PD-L1 analysis of resected tumors	Sometimes performed but not mandatory	Not applicable (no resections)

PD-L1, programmed death-ligand 1; NSCLC, non-small cell lung cancer.