THE CASE FOR CONTINUING PRIMARY CERVICAL SCREENING WITH CYTOLOGY RATHER THAN HPV TESTING

Abstract

HPV testing is used in several developed countries including the USA but has not yet found an established role in the UK cervical screening programmes. HPV testing is independent of the interpretive skills of the individual laboratory worker although the sensitivity of the test itself can be altered. New strains of the virus continue to be identified so the test can never be 100% accurate. It has been studied in women with mild or borderline dyskaryosis in their smear as a possible means of triage. If anything, however, HPV testing is too sensitive and lacks specificity. Its use resulted in too many women being referred for colposcopy putting a strain upon resources. Were it to be used in the same younger age groups as today's smears i.e. 20 onwards in Scotland, 25 and onwards in England then primary infections would be detected along with potential precancerous cases and again colposcopy clinics would be inundated. Thus, if HPV were to replace cytology in primary screening for cervical neoplasia it would be impractical before the age of 30 and the current common age for detection and treatment of cervical intraepithelial neoplasia (CIN) would have to be postponed, some early cases would be missed and some cancers would undoubtedly result. Girls are becoming sexually mature at an earlier age than their parents. Their sexual debut is also at an earlier age when lifelong monogamy is unlikely to result. Their opportunities for contact with genital strains of HPV are increased and cervical neoplasia may also develop sooner. Such cases would be missed. There would be further knock‐on effects if HPV testing were to replace cytology in primary screening. Cytology interpretive skills would be lost. It has been suggested that HPV testing be used for primary screening and cytology be confined to secondary examination of samples from HPV positive women. Although fewer personnel would be required to interpret those ‘smears’, they may have become a little less sharp. The beauty of HPV testing is the reliability of its negative predictive value. This could be put to good use combining it with LBC to get the best out of both worlds. Women could start 3 yearly cytological screening at 25 years. At 37 years, by which age most women would have developed viral immunity and entered a stable relationship, the LBC sample could also be tested for HPV. If both tests were negative the next tests could be postponed until 43 and then 49. It has been repeatedly shown in well‐screened populations that the incidence of CIN is extremely low in women from the age of 50 if they have been consistently negative until that point. As was the case with cytology and colposcopy which were shown to be complementary, cytology and HPV testing need not be mutually exclusive.