A validation study of the Focalpoint GS imaging system for gynecologic cytology screening.
We read with interest the article by Colgan et al concerning the sensitivity of the FocalPoint Guided Screening (FPGS) imaging system for gynecologic cytology screening compared with manual screening. To the best of our knowledge, their study represents the fourth large doubleblind study comparing manual and automated assisted screening, and demonstrated no difference in the performance of FPGS compared with manual screening in detecting low-grade squamous intraepithelial lesion or worse (LSIL1) and high-grade squamous intraepithelial lesion or worse (HGSIL1). However, the false-negative rates for LSIL and atypical squamous cells of undetermined significance (ASC-US) were significantly higher with FPGS than with manual screening. These results, in our opinion, suggest that the sensitivities of manual screening and image-assisted screening at the thresholds of ASC-US and LSIL are directly correlated with workload, and are similar to the conclusions we reached in our recent study. Although some studies have demonstrated an increased sensitivity associated with imaging systems, the most striking outcome has not been increased sensitivity, but rather increased workload and productivity. The US Food and Drug Administration-approved workload limits are doubled for image-assisted Papanicolaou tests, because imaged (field-of-view [FOV] only) slides are counted as “0.5” a slide compared with manually screened slides, which are counted as “1.0” slide. The literature now contains results from over 60,000 cases from 9 different laboratories as well as results from over 20 cytotechnologists that demonstrate that the maximum sensitivity of manual screening is directly correlated with screening workload, and that workloads exceeding 60 slides per day result in sensitivities that are lower than those of image-assisted screening (with an estimated absolute sensitivity of approximately 85%). In contrast, workloads below 60 slides per day appear to result in sensitivities that are significantly higher than those of image-assisted screening, workloads of 45 slides per day approach the sensitivity of human papillomavirus screening (as shown in the ARTISTIC study), and workloads near 30 slides per day have sensitivities approaching 100%. In the study by Colgan et al, reexamination of FPGS FOV images of HSIL, LSIL, atypical squamous cells-cannot exclude HSIL (ASC-H), and false-negative cases of atypical granular cells revealed that> 80% of reviewed FOVs had abnormal cells that were missed by the cytotechnologists. The authors point out that the sensitivity of FPGS may have improved if the cytotechnologists had evaluated the FOVs better. Other studies have also demonstrated that most false-negative cases were due to failure to identify abnormal changes present in at least 1 of the FOVs. These findings suggest that sensitivity may have improved if the cytotechnologists had spent additional time examining the FOVs. These conclusions have been corroborated in 2 recent, prospective, longitudinal studies that assessed the relation between workload and screening accuracy in imageassisted screening using the FPGS and ThinPrep imaging systems. In these latter studies, increased speed was accomplished mostly by a reduction in the time spent examining FOVs and a reduction in the percentage of cases that underwent full manual review. As workload increased, the time devoted to screening FOVs decreased, and cytotechnologists struggled to identify ASCUS and HSIL at higher speeds, leading to an increase in the number of misses. Given the data that are now available, what workload should medical directors allow for their cytotechnologists who perform manual or image-assisted screening? For manual screening, workloads of 60 to 70 slides per day can achieve sensitivities between 90% and 95%, whereas workloads of 30 slides per day can achieve sensitivities of> 95%. For image-assisted screening, the American Society of Cytopathology has recently published its recommendations for the cytotechnologist workload not to exceed 70 slides per day (an FOV-only slide was counted as 0.5 of a slide), recognizing that the current Food and Drug Administration upper limits of 100 slides per day can be associated with a significant reduction in sensitivity. Finally, there are obvious differences in expectations between the cytology laboratory and the general public regarding the sensitivity of the Papanicolaou test, because patients and litigators generally expect a false-negative rate of 0%. We know how an increased workload affects sensitivity and what level of sensitivity results from what workload. It would appear prudent for cytology organizations to begin considering how the differences in expectations from the community we serve and ourselves should best be resolved.