Frequency and outcome of cervical cancer prevention failures in the United States.

We measured the frequency and outcome of cervical cancer prevention failures that occurred in the Papanicolaou (Pap) and colposcopy testing phases involving 1,646,580 Pap tests in 4 American hospital systems between January 1, 1998, and December 31, 2004. We defined a screening failure as a 2-step or greater discordant Pap test result and follow-up biopsy diagnosis. A total of 5,278 failures were detected (0.321% of all Pap tests); 48% and 52% of failures occurred in the Pap test and colposcopy phases, respectively. Missed squamous cancers (1 in 187,786 Pap tests), glandular cancers (1 in 19,426 Pap tests), and high-grade lesions (1 in 6,870 Pap tests) constituted 4.1% of all failures. Unnecessary repeated tests or diagnostic delays occurred in 70.8% and 63.9% of failures involving high- and low-grade lesions, respectively. We conclude that cervical cancer prevention practices are remarkably successful in preventing squamous cancers, although a high frequency of failures results in low-impact negative outcomes.