The new algorithm for Primary screening with DNA-HPV test entiles citology triaging. The cytologist is aware that Pap tests are from a selected population at risk of
disease and is therefore more exposed to a risk of overdiagnosis rather than false negatives. A negative result of the Pap test does not refer the woman to the normal screening interval,
but to control at 1 year with HPV. The task of the Pap test triage is to bring the specificity of screening with HPV testing to acceptable levels, that means to distinguish, among women already selected by an extremely sensitive test, those who have obvious cytologic atypia and thus a greater risk of disease.
The Italian Group for Cervical Screening (GISCi) determined quality control recommended actions: (1) Assessment of the distribution of cytological diagnosis; (2) Calculation of the PPV for CIN2 + both total (ASC-US) and for every individual cytological diagnostic category; (3) Peer-review of normal and difficult cases; (4) systematic review of negative cytologies that at 1 year control show CIN 2 or more severe lesion (CIN2 +); (5) Fast rescreening of negative tests; (6) Adoption of a reporting system and uniform use of diagnostic criteria; (7) Circulation of standard set of triage Pap tests; (8) Comparative seminars, also with digital images, on complex cases of cytology triage. Moreover, quality indicators were set: (1) Percentage of abnormal cytologies (ASC-US); (2) Positive Predictive Value for CIN2+; (3) Percentage of positive Pap tests; (4) PPV of HPV+/citology+ for CIN2+ lesions; (5) Detection rate of histological lesions CIN2+ at recruitment; (6) Interval between test and invitation to 1 year repetition.
The percentage of positive tests showed high variability in pilot-studies, probably due to inexperience but also to adjustment of TBS 2001; standard will probably be established between 25% and 35%. In screening with HPV as primary testing, PPV for CIN2 + cytology triage must be significantly higher than the PPV of cytology screening with the Pap test as a primary test, since in the latter the abnormal cytology often come from women HPV HR-negative. The extensive automation of the molecular and the marked decline in cytology should
result in a reduction of the intervals between tests and reports.
AAVV. [Triage cytology in cervical screening programs using HPV test for primary screening]. Italian. Italian Group for Cervical Screening. 2013. www.GISCi.it