Since September of 1999, several members of the Regional Laboratory Alliance have offered liquid based methods for obtaining pap smears. Since this time, Saint Luke’s Regional Laboratories & Saint Luke’s Pathology Associates have screened more than 5,000 Thin Prep pap smears. The following is a comparison between the Thin Prep pap smear and the conventional pap smear.
During the time frame between September of 1999 and April of 2000, 3,758 Thin Prep pap smears were performed. 41 of these were considered unsatisfactory. 804 were diagnosed as atypical squamous cells of undetermined significance (ASCUS). 253 pap smears were reported as squamous intraepithelial lesions (SIL). In the same time frame, 18,590 conventional pap smears were performed. Of these, 111 were considered unsatisfactory for interpretation. 2,097 were diagnosed as atypical squamous of undetermined significance (ASCUS) and 478 were reported as squamous intraepithelial lesion (SIL). These results are summarized in the following table:
|
|
Thin Prep |
Conventional |
|
Unsatisfactory |
41 |
111 |
|
ASCUS |
804 |
2,097 |
|
SIL |
253 |
478 |
|
ASCUS/SIL Ratio |
3.2% |
4.4% |
|
Total |
3,758 |
18,598 |
Conclusions:
Atypical squamous cells of undetermined significance rated as a percentage of total pap smears varies with populations screened. Higher risk populations usually have higher ASCUS rates while lower risk populations have lower ASCUS rates. A way to compensate and equalize this difference is the ASCUS to SIL ratio. This ratio usually can account for variations in population. When comparing liquid based Thin Prep pap smears to the conventional pap smears, the ASCUS to SIL ratio is significantly decreased, from 4.4% for conventional pap smears to 3.2% for Thin Prep. This ratio suggests that the liquid based technology allows for more specific categorization into normal or SIL, reducing the percentage of ASCUS smears.
Michael Morgan, M.D.
St. Luke’s Pathology Associates, Inc.
Kansas City, Missouri