The ASC/SIL Ratio for Cytopathologists as a Quality Control Measure
The ASC/SIL Ratio for Cytopathologists as a Quality Control Measure
Monitoring the relative frequency of the interpretations of atypical squamous cells (ASC) and squamous intraepithelial lesions (SIL) has been proposed as a quality control measure. To assess its value, an ASC/SIL ratio was calculated every 6 months for 3.5 years, and confidential feedback was provided to 10 cytopathologists (CPs). By using simple regression analysis, we analyzed the initial and final ASC/SIL ratios for individual CPs and for the entire group. The ratio was below the upper benchmark of 3:1 for all but 1 CP during every 6-month period. The ratio for all CPs combined showed a downward trend (from 2.05 to 1.73). The ratio for 6 CPs decreased, and for two of them the decrease was statistically significant. One CP showed a statistically significant increase in the ASC/SIL ratio. The decrease for some CPs likely reflects the salutary effect of confidential feedback and counseling.
Atypical squamous cells (ASC) is the most common epithelial abnormality reported in Papanicolaou (Pap) test results. Currently, the Bethesda System for reporting Pap test results defines ASC as cells showing cytologic changes suggestive of squamous intraepithelial lesion (SIL) but with insufficient evidence, qualitative or quantitative, for a definite diagnosis of SIL. Because ASC is essentially a diagnosis of uncertainty, many laboratories monitor their ASC rates for quality control purposes to ensure that this interpretation is not overused. To control for differences in the frequency of cervical dysplasia in different populations, the ratio of ASC to SIL interpretations has been adopted as the preferred measure, especially for interlaboratory comparisons. Several benchmarks have been proposed and widely adopted: one is an upper benchmark of 35; another, used primarily for interlaboratory comparisons, includes upper and lower (95th and 5th) percentiles.
In a previous study, Juskevicius et al showed that measuring the ASC/SIL ratio of individual cytopathologists (CPs) and providing it to them periodically in a confidential communication is a useful quality control measure. It allows individual CPs to assess their ratio compared with that of the laboratory as a whole and against the 3:1 benchmark. We found no correlation between a CP's years of experience or annual gynecologic cytology case load and his or her ASC/SIL ratio. We did find a statistically significant decrease in the ASC/SIL ratio for our laboratory in a 3-year period during which CPs received feedback on their individual ratios. We could not be sure, however, whether the decrease in the ratio was due to the confidential feedback we provided, because there was at least one confounding factor: during that period, our laboratory converted from conventional Pap smears to liquid-based preparations. It was possible that the decrease in the ASC/SIL ratio during that time was due at least in part to this improved method for slide preparation.
Our aim in the present study was to extend our analysis for an additional 3.5-year period, after the conversion to liquid- based slide preparation had already been completed.
Monitoring the relative frequency of the interpretations of atypical squamous cells (ASC) and squamous intraepithelial lesions (SIL) has been proposed as a quality control measure. To assess its value, an ASC/SIL ratio was calculated every 6 months for 3.5 years, and confidential feedback was provided to 10 cytopathologists (CPs). By using simple regression analysis, we analyzed the initial and final ASC/SIL ratios for individual CPs and for the entire group. The ratio was below the upper benchmark of 3:1 for all but 1 CP during every 6-month period. The ratio for all CPs combined showed a downward trend (from 2.05 to 1.73). The ratio for 6 CPs decreased, and for two of them the decrease was statistically significant. One CP showed a statistically significant increase in the ASC/SIL ratio. The decrease for some CPs likely reflects the salutary effect of confidential feedback and counseling.
Atypical squamous cells (ASC) is the most common epithelial abnormality reported in Papanicolaou (Pap) test results. Currently, the Bethesda System for reporting Pap test results defines ASC as cells showing cytologic changes suggestive of squamous intraepithelial lesion (SIL) but with insufficient evidence, qualitative or quantitative, for a definite diagnosis of SIL. Because ASC is essentially a diagnosis of uncertainty, many laboratories monitor their ASC rates for quality control purposes to ensure that this interpretation is not overused. To control for differences in the frequency of cervical dysplasia in different populations, the ratio of ASC to SIL interpretations has been adopted as the preferred measure, especially for interlaboratory comparisons. Several benchmarks have been proposed and widely adopted: one is an upper benchmark of 35; another, used primarily for interlaboratory comparisons, includes upper and lower (95th and 5th) percentiles.
In a previous study, Juskevicius et al showed that measuring the ASC/SIL ratio of individual cytopathologists (CPs) and providing it to them periodically in a confidential communication is a useful quality control measure. It allows individual CPs to assess their ratio compared with that of the laboratory as a whole and against the 3:1 benchmark. We found no correlation between a CP's years of experience or annual gynecologic cytology case load and his or her ASC/SIL ratio. We did find a statistically significant decrease in the ASC/SIL ratio for our laboratory in a 3-year period during which CPs received feedback on their individual ratios. We could not be sure, however, whether the decrease in the ratio was due to the confidential feedback we provided, because there was at least one confounding factor: during that period, our laboratory converted from conventional Pap smears to liquid-based preparations. It was possible that the decrease in the ASC/SIL ratio during that time was due at least in part to this improved method for slide preparation.
Our aim in the present study was to extend our analysis for an additional 3.5-year period, after the conversion to liquid- based slide preparation had already been completed.
