Etiologies for non-correlating cervical cytologies and biopsies

To investigate the etiologies for discrepancies between cervicovaginal smear and corresponding cervical biopsy results, 615 patients with cytologic diagnoses of dysplasia or malignancy during 1 year were reviewed. Sixty-nine patients (11%) were identified in which the cytologic and histologic diagnoses differed. Utilizing an algorithm developed for the study, these cases were assigned an etiologic category for discrepancy: colposcopic biopsy or cytologic sampling, cytologic screening, histotechnical processing, histologic or cytologic interpretation. The most common cause for a discrepancy was colposcopic biopsy sampling (36 cases, 51%). There were nine errors (13%) in biopsy interpretation, with seven underdiagnoses and two overdiagnoses. Eight errors (11%) in cytologic interpretation occurred with half of these representing underdiagnoses. The other causes for discrepancy were less common--cytologic sampling (6 cases), histotechnical processing (3 cases), cytologic screening (2 cases), and a combination of factors (5 cases). Use of this algorithm allows laboratories to identify problem areas and design specific corrective protocols to improve diagnostic accuracy and patient care.