Testing automated liquid-based cytology samples with a manual liquid-based cytology method using residual cell suspensions from 500 ThinPrep cases

Abstract

We report a technical improvement upon a previously disclosed manual liquid-based cytology (MLBC) method; and, we use the improved method to prepare slides from residual ThinPrep specimens in order to see how often ThinPrep diagnoses correspond to diagnoses derived from exhaustive examination of their parent sample suspensions. Residual cell suspensions from 500 ThinPrep cases comprising (1) 20 low-grade squamous intraepithelial lesions (LSILs); (2) 200 high risk (HR) negatives and 20 ASC-US; and (3) 260 screening cytology specimens were studied. Institutional review committee guidelines allowed us to know diagnoses by groups of specimens, but did not allow us to know individual patient diagnoses, so we could not perform case-by-case matched outcome-comparisons. Cells were concentrated by conventional centrifugation and sedimented into a polymer gel that was then vortex-mixed and converted into a viscous cell-rich suspension. The cell suspension was smeared between two clean glass slides, which were air-dried and stained with the Papanicolaou stain. Two study-sets were created, comprising one slide from each case. Each of the two study sets was examined by two cytopathologists, and discordant diagnoses were adjudicated. Because of the ambiguity involved in the "atypical" (ASC-US, ASC-H, AGC) diagnosis categories, only outcomes at the level of LSIL or greater were recorded. All MLBC SILs were digitally imaged and abnormal slides plus digital images were sent to the laboratory that provided the residual automated liquid-based cytology (ALBC) suspensions. The final diagnoses were confirmed by the laboratory that provided the residual ALBC specimens. MLBC slides of the 20 LSIL cases afforded 2 high-grade squamous intraepithelial lesions (HSILs) and 18 LSILs. Those of the 200 HR-Negatives showed 3 HSILs and 30 LSILs; and those of the 20 HR-ASC-US showed 3 HSILs and 9 LSILs. MLBC slides of the 260 screening cytology specimens showed 1 Carcinoma, 3 HSILs and 20 LSILs; affording 3 HSILs and 14 LSILs more than originally diagnosed. The MLBC method of this report is useful for preparing cell suspensions for cytological examination. Our analytical method was exhaustive and used nearly all of the cell material that was provided to us for analysis; therefore, we conclude that this approach is useful for determining how well ALBC instruments represent their parent sample suspensions. It appears that "rare events" may be overlooked when limited sample aliquots are analyzed by ALBC instruments, and this probably accounts for our increased discovery of SILs by the MLBC method. Also, SILs often present as aggregates of cohesive cells which, if overlooked or ineffectively transferred to ALBC slides, would not be diagnosed.

Comparison of Cervical Cell Morphology Using Two Different Cytology Techniques for Early Detection of Pre-Cancerous Lesions

“…(Maksem et al, 2001). In this method membrane is formed from polymeric solution containing Carbowax and, agrose (Maksem et al, 2006) in which cells are suspended. Polymeric film is then applied on microscopic glass slide (Maksem et al, 2001).…”

Manual Liquid-Based Cytology: A Clinical Pilot Study of the VitroPrep™ Cytology Processing Kit

“…Additionally, the sampling protocol may have affected the results. Prior LBC studies have had the advantage of using residual fluid from the initial LBC Pap screening for evaluation of manual LBC methods [9,10,11,12]. However, since we were comparing 2 different LBC methods on women in clinical care, the VitroPrep sample was always taken second to ThinPrep sampling and this may have affected the quality of samples.…”

“…The studies that directly compared to conventional cytology reported unsatisfactory slides due to obscuring blood or clumped cells [13] and correlation with conventional cytology was reported as only 68% [14]. The other manual LBC studies describe satisfactory slides for interpretation though there was no comparison with conventional cytology [9,10,11,12]. Another low-cost method of cervical cancer screening used in low-income countries is visual inspection with acetic acid which requires no testing or expertise of a pathologist in making clinical diagnoses.…”

“…Manual LBC and conventional cytology are both low-cost procedures at USD 2-3 per slide, especially compared to the infrastructure investment of over USD 55,000 for current automated LBC systems [9]. Other manual LBC methods have been described [9,10,11,12] and compared to conventional cytology [13,14]. The studies that directly compared to conventional cytology reported unsatisfactory slides due to obscuring blood or clumped cells [13] and correlation with conventional cytology was reported as only 68% [14].…”

Accuracy of herpes simplex virus detection in liquid‐based (SurePath) Papanicolaou tests: A comparison with polymerase chain reaction

“…During the last decade, liquid-based Papanicolaou tests (LBPT) have become the mainstay of cervical cancer screening programs in the United States and other developed countries. These LBPTs, including lower cost manual methods that may be better suited for resource-limited settings [1][2][3] have resulted in improved sensitivity in the detection of squamous intraepithelial lesions. 4,5 They also have the advantage of providing the opportunity for ancillary molecular testing on the residual sample.…”