Applicability of Proficiency Testing (PT) Referral to Cytology/Histopathology Slide Staining by a Separate Entity

Staining of Cytology/Histopathology slides is considered part of specimen preparation and not part of the “examination” referenced in the CLIA definition of a laboratory. As such, entities that only conduct these preparatory steps to testing are not considered laboratories, and would not be subject to CLIA. • For purposes of Proficiency Testing (PT) referral, if a laboratory merely sends PT slides to a separate entity for staining and the slides are returned to the original laboratory for examination, CMS would not consider this to be PT referral.