Quality metrics in cervical cytopathology: A single institutional study

Objectives Implementation of quality control measures ensures acceptable performance by a laboratory. This study aims to assess the quality of cervical cytopathology reporting using quality metrics like atypical squamous cells (which include both atypical squamous cells of undetermined significance and atypical squamous cell -cannot rule out high grade squamous intraepithelial lesion)/squamous intraepithelial lesion (ASC/SIL), cytohistological correlation (CHC) and positive predictive value (PPV) of Papanicolaou (Pap) smears for squamous lesions of cervix. Methods A retrospective study of Pap smears from 2015 to 2020 was performed. The quality metrics analysed include diagnoses of ASCUS, ASC-H and ASCUS/SIL ratio, CHC and PPV. Cases with cervical biopsies/hysterectomy were included for CHC, and discrepancy was defined as discordance in diagnostic category between cytology and histology in the CHC. Results A total of 22,695 cervical cytology smears were reported. Unsatisfactory smears (n = 290) were excluded. Squamous lesions were reported in 233 smears, and the Bethesda system of nomenclature was followed. A definitive diagnosis (SILs and SCC) was given in 74% of cases. ASCUS and ASC-H were reported in 47 and 14 cases, respectively. The most common lesion on Pap smear was high-grade squamous intraepithelial lesion (HSIL; n = 92), followed by low-grade squamous intraepithelial lesion (LSIL; n = 64), and two were ungradable SIL. Squamous cell carcinoma (SCC) was reported in 14 smears. The ASC/SIL ratio was 0.38. CHC (n = 139) was 100% for ASC-H, LSIL, SCC and 84.7% for HSIL. A review of discrepant cases suggested sampling and interpretational discrepancy in five and one cases, respectively. The PPV of Pap smear for squamous lesions was 96.4%. Conclusion It is essential to have good quality cytopathology reports for early identification, which enables appropriate management. The most commonly used quality indicator for cytopathology is the ASCUS/SIL ratio. This study suggests the inclusion of the CHC and PPV values as quality metrics for Pap smear, since these are easily measurable and serve as a good indicator of quality in cervical cytopathology reporting.