Several studies suggest that HPV testing is more sensitive than cytology in primary cervical screening. These studies had different designs and were reported in different ways. Individual patient data were collected for all European and North American studies in which cytology was routinely performed and HPV testing was included as an additional parallel test. More than 60,000 women were included. The sensitivity and specificity of HPV testing were compared with routine cytology, both overall and for ages <35, 35-49 and 501. The age-specific prevalence of high risk HPV (hr-HPV) was also analysed. HPV testing was substantially more sensitive in detecting CIN21 than cytology (96.1% vs. 53.0%) but less specific (90.7% vs. 96.3%). The sensitivity of HPV testing was similar in all studies carried out in different areas of Europe and North America, whereas the sensitivity of cytology was highly variable. HPV sensitivity was uniformly high at all ages, whereas the sensitivity of cytology was substantially better in women over the age of 50 than in younger women (79.3% vs. 59.6%). The specificity of both tests increased with age. Positivity rates for HPV testing in women without high-grade CIN were region dependent. These results support the use of HPV testing as the sole primary screening test, with cytology reserved for women who test HPV positive. Large demonstration projects are needed to fully evaluate this strategy. ' 2006 Wiley-Liss, Inc.Key words: HPV testing; cervical screening; sensitivity; specificity; primary screening Currently in Europe and North America, cervical cancer screening is based on exfoliative cytology performed at intervals ranging between 1 and 5 years. Although there has been a marked reduction in incidence and mortality rates of squamous cell carcinoma of the cervix in countries with established cytology screening programmes, 1-3 Sasieni et al. (1996) reported that 47% of women in the UK who developed stage 1B1 or worse invasive cervical cancer before the age of 70 had had an adequate previous screening history. 2 The weaknesses in cytology are 3-fold. First, results are dependent on the high quality sample being collected during examination. Second, the test requires the identification of morphological changes within cells, whose interpretation is highly subjective. Last, this method of screening is particularly repetitive, which can lead to a greater number of interpretive errors. False negative cytology has major medical, economic and legal implications, and this is reflected in high malpractice litigation costs in the US associated with misreading cervical smears.Interest in the use of HPV testing as a screening test is based on the finding that HPV DNA is present in almost all cervical cancers, 4 and the availability of easily performed tests, which have demonstrated higher sensitivity for high grade CIN (CIN21) than that achieved by cytology in several studies. This higher sensitivity offers several potential advantages, including reduced cancer rates and longer screening intervals, ...