Interobserver variability in the interpretation of cervical smears - a must for developing an internal laboratory quality control system

I. Bălulescu, M. Badea

Abstract: Interobserver variability means differences among different medical observers who consistently may score patients at different risk levels. Due to the intrinsic degree of subjectivity in cytological interpretation that may lead to false negative results, the interobserver variability and its implication in patient’s care justify the need for implementing a routine laboratory system for quality assurance. The objective of this study was to analyse the interobserver variability in classifying cervical precancerous lesions in the specialised cyto-pathology laboratory of Bucharest Micomi Clinic, which receives about 60000 slides/year, in order to improve its quality assurance system. We conducted a retrospective study on 46934 slides evaluated as satisfactory and having been read by at least two qualified professionals, out of which we selected 774 cases (1.64%) with different interpretations. The discordant results have been split into six categories: I) positive at primary lecture, negativated by the pathologist; II) positive with a disagreement of at least one premalignancy level; III) negative at first lecture, positive at review; IV) difficult cases; V) interobserver variability by staff background; VI) third level of re-examination. The highest level of interobsever variability was at the limit between negative results with intense reactive changes and minimum atypical changes(ASC-US category). Consequently, this equivocal category has been included in the list of circumstances that are routinely submitted to a double lecture in the laboratory as a measure to reduce to a minimum level the ineluctable false negative rate of cytology. A relative lower level of discordances was noted on liquid based slides.
DOI:10.18643/gieu.2013.178

Keywords: cervical cancer screening, quality control, cervical cytology, interobserver variability, atypical squamous cells