Current techniques for obtaining a Papanicolaou smear are reported to have false-negative rates of up to 50 percent. Sampling technique may influence this rate by failing to obtain cells or by yielding samples that contain blood or debris. Eisenberger and colleagues investigated the usefulness of a clinical recommendation that obtaining the ectocervical sample before the endocervical sample improves the quality of the Pap smear.

The study was conducted at a university gynecology clinic. During one phase of the study, residents obtained the endocervical sample before the ectocervical sample. During the other phase, the ectocervical sample was obtained first. An endocervical brush was used to obtain the endocervical sample, and an Ayre spatula was used to obtain the ectocervical sample. The 500 samples obtained by each sequence were reviewed by the same team of cytotechnologists and pathologists, who were blinded as to the order of sampling.

Inadequate samples were defined as those without an endocervical component, smears that were too thick or were obscured by blood or inflammation, and those with air-drying artifact. When the endocervical sample was obtained first, 405 (81 percent) of the smears were adequate. When the ectocervical sample was obtained first, 410 (82 percent) of the samples were adequate.

The two sequences for obtaining cells differed significantly in the proportion of smears obscured by blood. When endocervical samples were obtained first, 22 (4.4 percent) of the samples were obscured by blood. In contrast, this was a problem in only three (0.6 percent) of the samples in which ectocervical cells were obtained first. The difference in the number of low- or high-grade squamous intraepithelial lesions identified by the two techniques was statistically significant. With ectocervical sampling preceding endo-cervical sampling, 55 (11 percent) of the samples revealed such lesions, compared with 35 (7 percent) of the samples when the endocervical sample was obtained first.

The authors conclude that using the Ayre spatula to obtain the ectocervical sample first, followed by use of the endocervical brush to obtain the endocervical sample, improves the quality of Pap smears, primarily by reducing the number of samples that are obscured by blood.