The effect of the quality of Papanicolaou smears on the detection of cytologic abnormalities

BACKGROUND Controversy continues regarding the relation between the quality of Papanicolaou (Pap) smears, especially the presence of endocervical cells (ECC), with the finding of cytologic abnormalities. METHODS As part of a study regarding performance feedback on the quality of Pap smears, data from 56,475 Pap smears obtained by 176 participating clinicians over a 20-month period were analyzed to assess the relation between the presence of ECC, the categorization of global specimen adequacy as “satisfactory” or “satisfactory with limitations,” and the prevalence of atypia and squamous intraepithelial lesions (SILs). RESULTS Atypia was less likely to be found in “satisfactory” Pap smears than in “satisfactory with limitations” quality Pap smears (odds ratio [OR], 0.6; 95% confidence interval [CI], 0.5–0.6; P < 0.001), even though the latter could contain ECC. No association was found between satisfactory Pap smears and cytologic abnormalities. Compared with specimens with no ECC, an ECC count of ≥ 50 on a slide was associated positively with the detection of atypia (OR, 2.1; 95% CI, 1.8–2.4; P < 0.001) or SILs (OR, 1.7; 95% CI, 1.3–2.2; P < 0.001). A similar relation existed between ECC counts of 25–50 (OR, 1.9; 95% CI, 1.1–2.2; P = 0.01) and the detection of SILs. No relation was found between specimens with < 25 ECC and the presence of atypia or abnormalities. CONCLUSIONS The global adequacy criterion of “satisfactory” assigned to a Pap smear does not indicate that there is a greater likelihood of detecting cytologic abnormalities compared with lower quality Pap smears. To the authors' knowledge, previous studies regarding the link between ECC in the Pap smear and cytologic abnormalities have not addressed the relevance of how many ECC are needed to maximize the identification of abnormalities. The data from the current study support the value of obtaining at least 25 ECC as a quality indicator of sampling. [See editorial on pages 103–4, this issue.] Cancer (Cancer Cytopathol) 1999;87:113–7. © 1999 American Cancer Society.