Joel S. Bentz, MD
All laboratories that are using molecular methods to test for high-risk types of human papillomavirus (hrHPV) DNA are required to have a license for testing and to participate in annual proficiency testing for hrHPV, per the Clinical Laboratory Improvement Amendments of 1988. Laboratories that do molecular testing for hrHPV but do not participate in a general virology proficiency test are required to participate annually in three events, each consisting of five challenges.
The reference for this requirement is CLIA, subpart H, section 493.831 Standard; Virology at wwwn.cdc.gov/clia/: “Failure to attain an overall testing event score of at least 80 percent is unsatisfactory performance” and “Failure to participate in a testing event is unsatisfactory performance and results in a score of 0 for the testing event.” Subpart I, section 492.919 outlines the proficiency test provider responsibility: “To be approved for proficiency testing in virology, a program must provide a minimum of five samples per testing event. There must be at least three testing events at approximately equal intervals per year.”
The CAP Human Papillomavirus (High-Risk) Survey for Cytopathology and Other Laboratories (CHPV) meets the CLIA requirement for a program of three events and five samples per event. It is the only hrHPV proficiency test available in the United States that is specific to transport/ preservative media type, and it includes all of the commercial liquid-based cytology media used for gynecologic cytopathology. The purpose of this qualitative Survey is to determine presence or absence of hrHPV. The hrHPV samples are unique since the participant lab is required to take the samples through preanalytic, analytic, and postanalytic steps. This enables laboratories that use cell lysis as part of their procedure to test this step. Testing all phases ensures the accuracy and reliability of test results. The viral material was obtained from human epithelial cells (SiHa cells) containing integrated genome of HPV subtype 16 grown in tissue culture and then fixed and preserved in an ethanol solution. These were suspended in three types of transport/preservative media.
The CHPV Survey has four different modules so users can select the sample type(s) received in their laboratory. In 2008, the CHPV Survey material was compatible with Digene Hybrid Capture and Third Wave Invader reagents. The Third Wave Invader analyte-specific reagents have subsequently been FDA approved and now are marketed by Hologic as Cervista HPV HR. Laboratories that use other commercial kits or a user-developed assay can also use this Survey material. The Survey modules include one for Digene media (CHPVD), ThinPrep media (CHPVM), SurePath media (CHPVK), or a combination of the three media types (CHPVJ). Only laboratories that receive all three sample types should enroll in CHPVJ.
The CHPV Survey consisted of three mailings of five challenges each. One of the three mailings included a demographic survey of laboratories. The survey showed that there was an increase in the number of cytology labs that perform HPV testing, up from nine percent in 2006 (Moriarty AT, et al. Arch Pathol Lab Med. 2008;132:1290–1294) to 20 percent in 2008. It is no surprise, then, that 16.8 percent of participants said cytotechnologists perform the HPV test. An encouraging finding was that 32.4 percent of participant labs reported performing low-risk HPV testing on cervicovaginal specimens. This is a decrease from 44 percent found in our 2006 demographic survey. An interesting development is that 61 percent of participants report using the same cytology vial to perform testing for Chlamydia, gonorrhoeae, or both. The survey found that in many labs, individuals who perform HPV testing do not have MP(ASCP) certification in molecular pathology.
In 2008, we analyzed 3,296 participant lab responses from hrHPV challenges. The participant response to each challenge could include negative, positive, and indeterminate. The responses were as follows: 1,461 positive, 40 false-negative, 16 false-positive, 1,764 negative, and 16 indeterminate. Overall, 24 percent were Digene media challenges, 51 percent ThinPrep media, and 24 percent SurePath media. Eighty-two percent of labs used the Digene Hybrid Capture II (HC2) assay to complete the challenge. Nine percent used Third Wave Invader, three percent used other commercial kits (for example, in situ hybridization), and four percent used a user-developed assay (for example, PCR).
Concordance rate to the reference result for all challenges was 98.3 percent overall, with 1.2 percent false-negative and 0.5 percent false-positive. By media type, the concordance rate was 97.7 percent Digene, 98.8 percent ThinPrep, and 97.8 percent SurePath. By assay type, the concordance rate was 99.5 percent HC2, 97.2 percent Third Wave Invader, 86.7 percent other commercial kit, and 100 percent user-developed. We analyzed the effect of the various combinations of media and assay types and found the highest concordance rate (100 percent) for user-developed assays with all three media types. This was followed by a combination of HC2 plus ThinPrep (99.6 percent), Third Wave Invader plus ThinPrep (99.4 percent), HC2 plus SurePath (98.8 percent), HC2 plus Digene (97.9 percent), and Third Wave Invader plus SurePath (94.1 percent). The lowest concordance rate was seen with the combination of other commercial kit plus ThinPrep (86.2 percent) or SurePath (86.1 percent).
Last year, 2008, was the first full year of the CHPV Survey. Additional analysis will be forthcoming as more participant response data become available.
Laboratories can still enroll in the CHPV 2009 B and C mailings. There are four different modules of CHPV; if your laboratory receives two sample types, choose one module to satisfy the requirement for enrollment. The module to order depends on the sample source as follows: Digene transport media, CHPVD; SurePath transport media, CHPVK; Cytyc Preservcyte media, CHPVM; and Digene, SurePath, Cytyc media (vials of each in every event), CHPVJ.
Please call CAP customer service at 800-323-4040 if you would like to order the CHPV Survey.
Dr. Bentz, a member of the CAP Cytopathology Resource Committee, is professor of pathology, University of Utah, Salt Lake City.