This method of producing control material establishes consistency in the TEQA comparative assessment process, counters selection bias and reduces the time demands associated with slide selection. It may also prove useful in identifying technical problems within laboratories during sample preparation prior to or during staining, including equipment or process faults. This technique is now well established locally as an enhancement of the current TEQA scheme for the assessment of slide staining. We feel that this enhancement could be incorporated as a new initiative in the current National TEQA scheme as a complement to the established selection process.
Technical external quality assessment (TEQA) in Wales is based on NHSCSP publication 19, which sets out policy and procedures for the scheme. The purpose of EQA is to sustain and improve the quality of patient care by promoting a high standard of performance. Following the introduction of liquid base cytology (LBC) technical limitations, particularly in assessing counterstaining, have been noted. LBC provides the means to address these limitations ‐ As part of a development plan for TEQA in Wales, a control sample procedure was introduced to the scheme. A pooled control sample was composed, containing residual material from six ‘matched’ negative samples, re‐suspended in collection fluid. Aliquots of this sample were distributed for processing and staining, to the 13 laboratories registered with the scheme. The slides produced were assessed at a scheduled TEQA assessment in accordance with the standard criteria. Initial overall scoring for these control samples produced acceptable levels of staining for 12 of the laboratories ‐ one laboratory produced a marginal score. Repeat distributions have shown maintained or improved results. This method provides a prospective quality assessment tool, which counters the emphasis on slide selection and eliminates potential selection bias, whilst introducing consistency and improving comparability across participant laboratories. The method may also prove helpful in identifying technical inconsistencies such as equipment or handling errors that may occur during sample processing prior to or during staining. The control process, which is now used routinely in the Welsh TEQA scheme; is considered complimentary to, and not a replacement for, the selection process established in NHSCSP #19. However, we feel that this development could be considered as a new initiative in the National TEQA scheme. The control process is applicable to all LBC systems in current use.
The use of computer assisted screening (CAS) in cervical screening is established in the USA and Europe and is currently undergoing trials in the UK (HTA). Following the introduction of SurePath™ LBC technology to Wales, Cervical Screening Wales (CSW) has implemented a study into applications of CAS within the CSP in Wales, agreed during LBC procurement negotiations. Technological support was provided by TriPath Europe and Medical Solutions UK Ltd. Evaluation centred on the use of CAS in Quality Assurance procedures, comparing it with rapid screening (review and preview), as HTA studies are already established to assess the primary screening role.
Assessment included
• Evaluation of CAS across a laboratory network – assessing sample identification, tracking processes and transportation
• Assessment of Quintile Ranking verses abnormality distribution
• Assessment of the NFR (no further review) category as a reliable indicator of sample negativity
• Monitoring screener performance using CAS: Focal Point/LGS has the capability to monitor operator/observer functions
Three laboratories in North Wales participated in the study. Slides were scanned centrally using Focal Point LGS and returned to laboratories for assessment.
Slide assessment followed a twin track protocol.
• The ‘manual’ arm assessed slides according to standard laboratory procedures
• The ‘CAS’ arm assessed slides using location guidance and screening
Data were collected and analysed by CSW. Approximately 12 000 samples were scanned; results were compared for both arms.
Results show that the technology has a number of benefits, in supporting and enhancing performance within the screening programme.
• CAS compares favourably with rapid screening
• Quintile ranking data reflects the distribution of abnormalities
• The technology is well suited to shared use through laboratory networks
• Variations in screener aptitude were noted.
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