The efficacy of liquid-based cervical cytology using direct-to-vial sample collection

Previous studies of liquid-based cervical cytology (LBCC) have used a split sample collection technique that creates a potential negative bias for its evaluation. Thus, the full diagnostic potential of LBCC has not been established. The purpose of our study was to determine rates of specimen adequacy and cervical cytologic and histologically confirmed diagnoses obtained with a liquid-based Papanicolaou (Pap) test using a direct-to-vial sample collection technique and compare these results with those obtained using the conventional Pap test (CPT).

A total of 1004 nonpregnant women aged 18 years or older with an intact cervix had Pap tests collected with an Ayre spatula and cytobrush, and the sample was placed in a preservative solution. The specimens were processed as thin layer Pap tests according to the manufacturer's specifications. Another group of 2110 women with a similar patient profile had a CPT collected immediately preceding the initiation of the trial. The subjects in each group consisted of an equal percentage of women presenting for a routine Pap test or a colposcopy examination. We compared the distributions of diagnostic categories between the groups using a chi-square test.

A significantly greater percentage of satisfactory Pap tests were obtained using LBCC (84.0%) compared with the CPT (60.5%, P < .001). Fewer satisfactory but limited by (SBLB, 14.8%) and unsatisfactory (1.2%) Pap tests were reported using LBCC compared with the CPT (35.7% and 3.8%, respectively, chi2 = 170.7, P < .001). A significantly greater percentage of low-grade squamous intraepithelial lesion (LSIL) and high-grade squamous intraepithelial lesion (HSIL) Pap test results were reported using LBCC (7.4% and 3.7%, respectively) compared with the CPT (1.7% and 1.7%, respectively, chi2 = 74.4, P < .001). The predictive value of a positive LBCC test (93.9%) was similar to that for a positive CPT (87.8%) when compared with histology results.

Compared with the CPT, LBCC detected a significantly greater percentage of satisfactory Pap tests and significantly reduced the number of unsatisfactory and SBLB tests. Four times the percentage of LSIL and twice the percentage of HSIL Pap test results were obtained using LBCC compared with the CPT. These findings demonstrate that LBCC significantly improves the adequacy of Pap tests and may increase the rate of detection of cervical neoplasia compared with the CPT.