A Quality Improvement Study to Evaluate Discordance Rates of Low-Grade Squamous Intraepithelial Lesion on Cervical Pap Smears with Histopathologic Correlation

Summary: Introduction: An accredited cytology laboratory continually strives to implement quality control and improvement measures, to ameliorate patient care. This study aims to assess the frequency and accuracy of low grade squamous intraepithelial lesion (LSIL) as detected in cervical Pap smears by comparing it with concurrent but discordant histopathology. Materials and Methods: A retrospective quality improvement study for the year 2023 was conducted and 1136 women received a diagnosis of LSIL. Out of these, 104 women had a discordant histopathologic diagnosis. Patient's age, human papillomavirus (HPV) status, cytology diagnosis, histopathology diagnosis, specimen type and data on correlation at time of sign out were collected. All the cytology and histopathology slides for each discordant case were re-reviewed independently by pathology trainees (2 board-certified and 1 board-eligible) followed by a consensus. Results: 104 women with a mean age of 38.5 years were diagnosed with LSIL on Pap smear but had a discordant histopathological diagnosis. Discordance with cytology was reported in 84 histopathology cases at the time of sign out but review of cytology slides at at that time was documented in only 2 cases. The retrospective independent and consensus reviews revealed that the transformation zone was not present in 36 histopathology specimens, inadequate endocervical curettage or cervical biopsy sampling was present in 22 cases, and inflammation or atrophy was present in 7 cases. Four cytology cases were downgraded from LSIL to atypical squamous cells of undetermined significance (ASCUS) after trainee review. Independent re-review of these cases by four board-certified cytopathologists found that at least 1 cytopathologist agreed to downgrade 3 of the cases while only 1 case had majority agreement for a diagnosis of ASCUS. There was a high rate of prevalence of high risk HPV strains (78%). (Table 1) Conclusions: Quality improvement measures are essential to enhance patient care. Our institution has a high rate of discrepant histopathologic diagnoses when the initial cytology diagnosis is LSIL (9%). This study shows that in our institution, immediate re-review of the cytology slides in this specific scenario is not necessary since there is a very low rate of cytology diagnosis change (majority agreement for downgrade to ASCUS is less than 1%). The main cause of discrepancy in our institution is a high rate of inadequate sampling for histopathologic evaluation in these patients.