Superior performance of liquid-based versus conventional cytology in a population-based cervical cancer screening program
Introduction
Worldwide screening programs for cervical cancer based on the Papanicolaou (PAP) smear have contributed to the decrease in incidence and mortality of cervical cancer [1]. Nevertheless, both false-negative and false-positive results due to sampling and screening errors are well-recognized problems. Liquid-based cytology was introduced as an alternative to conventional cytology screening in the hope of improving specimen adequacy and sensitivity in detecting cervical abnormalities. Various studies have shown that liquid-based cytology is more effective in the detection of cervical intraepithelial neoplasia (CIN), reduces the number of unsatisfactory specimens, and reduces screening time compared to conventional cytology [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13].
A nationwide, government-sponsored cervical screening program has been operative in the Netherlands for more than 25 years. All a-symptomatic women between 30 and 60 years of age are invited by the local health authorities to participate in this screening program. At 5-year intervals cervical cytology samples are taken by general practitioners and sent to regional pathology laboratories. In the region of Southwest Holland, 56% of women within the defined population participate in the program [14], [15]. Ninety five percent of the smears are sent to one laboratory. Despite this quality-controlled, well-organised, population-based screening program, the proportion of false negative smears is about 20% [16]. Therefore, we introduced a liquid-based cytology system (SurePath®, BD Diagnostics, Tripath, Burlington, NC 27215 USA) in this region in 1997 to study the effectiveness of this method in comparison with conventional cytology.
We investigated the sensitivity and specificity of these two screening techniques in a group of 86,469 women participating in a population-based screening program. We compared the outcome of the two screening methods with regard to the detection rate of histological abnormalities. The false negative rate was investigated using our nationwide pathology database containing both cervical cytology as well as histology results for all women. By using this database we were able to achieve 100% of follow-up in cases with subsequent biopsies.
Section snippets
Patients and screening methods
This study was conducted in one pathology laboratory in Southwest Holland that screens Pap specimens obtained from approximately 500 general practitioners. The material consisted of samples from asymptomatic 86,469 women (age 30–60) participating in the national screening program, collected during the period July 1997–June 2002. This age window was chosen as a result of the inclusion criteria put forward by the national screening program. The women chosen were a-symptomatic according to the
Patient characteristics
Samples were collected from 86,469 women between the ages of 30 and 60. The study cohorts consisted of 51,154 conventional smears (conventional cohort) and 35,315 liquid-based cytology slides (Cohort 2). There was no difference in age-distribution between the two cohorts (average 43.9 years vs. 43.7 years of age).
Cytology
Cytology results within the two cohorts are shown in Table 1. The percentage of unsatisfactory slides based on liquid-based cytology (Cohort 2) was significantly less compared to
Discussion
A Nation-wide screening program for cervical cancer has been operative in the Netherlands since 1975. Although this program is well controlled and uses skilled cytotechnologists, a false-negative rate of about 20% for HSIL or higher lesions has been observed [16]. Methods to reduce the false–negative rate were investigated including the introduction of liquid-based cytology.
Various studies have reported the advantages of liquid-bases cytology over conventional cytology [2], [13] but
Conflict of interest statement
The authors do not declare any conflict of interest, nor any financial support by SurePath®, TriPath Imaging, Inc., Burlington NC, USA for performing this study.
Acknowledgments
The National Pathology Database PALGA is gratefully acknowledged. This study could not have been performed without the support and enthusiasm of the primary health care physicians within our region, as well as the cooperation from patients.
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