Page 70 - Screening for Cervical Cancer: Systematic Evidence Review

Chapter IV. Discussion

Major Findings and Limitations of the Literature

Who Should be Screened and How Often?

We focused this question on screening among women age 65 and older and for those who

have had a hysterectomy and on identifying research that directly compared methods of selecting

screening interval. In summary, all the available evidence is observational, predominantly from

large population-based data sources and from a small number of prospective cohort studies.

Given these sources of information, the findings of these studies are highly coherent and support

the following conclusions:

• The risks of high-grade cervical lesions and cancer fall with age.

• A history of prior normal Pap tests further reduces risk.

• If screening recommendations are not modified with age, older women are

disproportionately likely to have evaluations for false-positive findings.

Among previously screened women with a history of normal Pap tests, fewer than 1

individual per 1,000 screened (in some scenarios as few as 1 per 10,000) screened will have a

high-grade cytologic abnormality. As an example, if the sensitivity of cytology is 60 percent and

the specificity is 98 percent for detection of high-grade abnormalities, then 34 women will be

evaluated for high-grade squamous intraepithelial lesion for each true high-grade cervical lesion

identified; moreover, two high-grade lesions will have been missed by cytology for every three

cases identified. The ratio of true positives to false positives is much higher if low-grade

cytologic changes are considered. In unpublished work, Sawaya and colleagues’ report that 231

additional procedures — 112 extra Pap tests, 33 colposcopies, 30 biopsies, 35 endocervical

curettages, 8 endometrial biopsies, 4 dilation and curettages, 7 loop electrosurgical excision

procedures, and 2 cone biopsies — were done in response to 110 Pap tests reported as atypical

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