The number of dyskaryotic cells on an initial ThinPrep cervical sample showing mild dyskaryosis has predictive value

Estimation of disease severity in the NHS cervical screening programme. Part II: quantitative methods of estimating disease severity and progression potential

OBJECTIVE

This is the second of a two-part paper exploring the use of a more quantitative approach to both cytology and histology disease severity measurements. In Part I the problem of artificial cut-off points was discussed and a semi-quantitative solution to the problem proposed. In Part II quantitative methods are proposed that are used to predict the estimated progression probability (EPP) to invasive cancer.

METHODS

Based on models derived from published data the grade number (GN) is related to the EPP to invasive cancer over the next 10 years for both cytology (CEPP) and histology (HEPP) using a look-up table. CEPP and HEPP are then adjusted by other factors such as age, persistence, HPV result, number of cells and lesion size to obtain the adjusted CEPP and HEPP (ACEPP and (AHEPP). The two factors can be combined to produce an adjusted weighted estimated progression potential using the formula AWEPP √((ACEPP + AHEPP)/2) × AHEPP) using a two to one bias in favour of the histology.

RESULTS

As an example of the methodology consider a slide estimated as showing a 60% probability of moderate dyskaryosis (HSIL favouring CIN2) and 40% probability of mild dyskaryosis (LSIL favouring CIN1). The GN number would be 1.6 (as described in Part I) and the EPP over the next 10 years 0.78%. For a woman aged 52 years (correction factor ×2.0) with a second mildly dyskaryotic smear (correction factor ×1.25) and >50 dyskaryotic cells (correction factor 1.5) the ACEPP would be 0.78 × 2.00 × 1.25 × 1.5 = 2.9%. If the HEPP on histology was 50:50 between CIN1 and CIN2, the AHEPP can be calculated as 1.4%. The AWEPP would be √((2.9 + 1.4)/2 × 1.4) = 1.7%. The final estimate of disease progression potential based on both cytology and histology is 1.7% over 10 years.

CONCLUSIONS

These quantitative approaches based on adjusted and weighted EPP provide a framework suitable for research, audit and comparison between screening centres, and for tailoring criteria for colposcopy referral and treatment. Further research is required to improve the estimates given in the paper.

Decrease in numbers of glandular cell groups in post-LLETZ liquid-based cytology preparations

OBJECTIVE

Large loop excision of the transformation zone (LLETZ) has become standard of care in the management of cervical squamous neoplasia and with cone biopsy glandular intraepithelial neoplasia. Controversy remains about the long-term effects of this traumatic procedure. The aim of this study was to count and compare the number of endocervical glandular cell groups in pre- and post-LLETZ cervical preparations using liquid-based cytology to establish a cyto-morphological correlate of destruction of the transformation zone.

METHODS

The cytology/histology correlation audit records of the Cytopathology Department of St Luke's Hospital in 2003 and early 2004 were used to select patients with a cytological diagnosis of high grade dyskaryosis followed by LLETZ. Only those cases with post-LLETZ cytological follow-up were selected. Cases using conventional smears were excluded. One hundred and twenty slides (60 pairs of slides) in total were retrieved. The cases underwent review and all groups of >3 glandular cells in each slide were counted by AM while blinded as to whether smears were pre- or post-LLETZ. Medians were compared using a Mann-Whitney U-test.

RESULTS

The median number of groups of endocervical glandular cells of the pre-treatment group was 5.5 and of the post-treatment group was 2.0. There were significantly fewer endocervical glandular cell groups in the post-LLETZ population (P = 0.03).

CONCLUSIONS

The number of endocervical glandular groups in cervical cytological preparations decreases significantly following LLETZ procedure. This suggests that cytological follow-up may not be as useful in glandular neoplasia cases. Few or absent glandular cell groups in post-LLETZ preparations may have implications for adequacy assessment.