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Publication, Part of

Cervical Screening Programme, England - 2019-20 [NS]

Official statistics, National statistics

National Statistics

Section 2: Cervical cytology

Overview

Cervical cytology refers to the process of screening samples of cells for abnormalities.

The steps that make up that process are detailed below.



Changes to cervical screening policy

In May 2013 a HPV primary screening pilot was launched whereby cervical samples are first tested for HPV.

This differs from HPV test as triage screening where samples are examined under a microscope by a cytologist for signs of abnormality. 

If a sample is found to be HPV negative, the woman is returned to routine recall. If a sample is found to be HPV positive, a slide is prepared from the same sample and examined by a cytologist.

Women who have a HPV positive screen with a cytology negative result, will be recalled in 12 months for a further screen. Women who have a HPV positive screen with an abnormal cytology result are referred to colposcopy.

Women with 2 consecutive HPV unavailable or cytology inadequate screening tests in any combination will be referred to colposcopy. For further details see the data quality statement.


Inadequate samples (GP and NHS Community Clinics)

An inadequate sample result can be assigned following a test outcome of either HPV unavailable or cytology inadequate.

Women who have an inadequate sample are either tested again or referred to colposcopy.

Colposcopy referrals are made following either:

  • a third consecutive inadequate cytology result (under HPV test as triage screening).
  • 2 consecutive HPV unavailable or cytology inadequate screening tests in any combination (under HPV primary screening).

The proportion of inadequate samples has fallen since the introduction of Liquid Based Cytology (LBC) in 2004-05.

Before the introduction of LBC technology, rates of inadequate samples submitted by GP and NHS Community Clinics (NHSCC) for women aged 25 to 64 were between 9% and 10% each year.


In 2019-20, 1.2% of all samples were inadequate, a decrease from 2.3% in 2018-19.

The reduction in inadequate samples in 2019-20 is thought be related to the implementation of HPV primary screening. Under HPV primary screening, a HPV negative result means cytology is not required. Therefore cytology tests, which have a higher rate of inadequate results, are used less often.

 


The proportion of inadequate samples was higher in older age bands in 2019-20, 55 years and above. The chart below shows that the proportion of inadequate samples reduced in all age bands in 2019-20 compared to 2018-19.
 


In 2019-20, for women aged 25 to 64, 2 laboratories had inadequate rates over 6%, with most (41 of 45) recording rates less than 4%.


Adequate samples (GP and NHS Community Clinics)

In 2019-20, for women aged 25 to 64:

  • 95.7% of samples were reported as being negative.
  • 1.5% of tests were found to have borderline changes.
  • 1.9% of tests were reported as low-grade dyskaryosis.
  • Women below the age of 30 were amongst those most likely to have an abnormal test result (see data table 15).
Test result Number %
Negative 2,856,761 95.7
Borderline changes 44,025 1.5
Low-grade dyskaryosis 56,811 1.9
High-grade dyskaryosis (moderate) 13,157 0.4
High-grade dyskaryosis (severe) 14,158 0.5
High-grade dyskaryosis/?invasive carcinoma* 442 0.0
?Glandular neoplasia (endocervical)* 1,013 0.0
Total adequate samples 2,986,367 100.0

* ?invasive carcinoma means ‘suspected invasive carcinoma’, ?glandular neoplasia (endocervical) means ‘suspected glandular neoplasia of endocervical type’
NB. The sum of components may not equal totals due to rounding.
Source: KC61, NHS Digital. See data table 15.


Time from receipt of sample to authorisation of report

The percentage of laboratory tests authorised (test confirmed) within 2 weeks fell from 61.9% in 2018-19 to 61.7% in 2019-20.

Prior to 2016-17 the percentage authorised within 2 weeks had been above 90% since 2010-11.

The increase in time to authorisation of reports in recent years is attributable to the time taken to implement HPV primary screening. This has affected capacity in laboratories due to reduced workforce. Further details can be found in Appendix J.


Regional versions of the chart above are available in the interactive report accompanying this publication.

Data for the 3.28 million samples authorised in 2019-20 is broken down further in the chart below.


Outcome of colposcopy referrals

There are 2 main colposcopy referral groups

Women referred after a single occurrence of a potentially significant abnormality

Outcomes where the most significant result was either a high-grade dyskaryosis (moderate), high-grade dyskaryosis (severe)/invasive carcinoma or glandular neoplasia (endocervical).

Women referred to colposcopy for other reasons

Women with a first test result showing borderline change or low-grade dyskaryosis where they also test positive for HPV.

Persistent inadequate results:

 HPV testing as triage: Following a third consecutive inadequate cytology result.

 HPV Primary: Women with 2 consecutive hrHPV unavailable or cytology inadequate screening tests in any combination will be referred to colposcopy.

For referrals after a potentially significant abnormality where the sample was registered between April and June 2019, 59.7% were found to have the most severe conditions of cervical cancer, cervical intraepithelial neoplasia (CIN3) or adenocarcinoma in situ.

This compares to 4.8% for referrals following non-negative samples.


Standards and indicators for laboratory reporting

Standards

The distribution of individual laboratory results is used by the programme for quality assurance purposes in monitoring performance.
Where laboratories fall outside specified ranges (standards) there is a requirement to investigate the reason(s) for this.

The standards which laboratories are required to adhere to are outlined in cervical screening programme standards.

There are 3 key values used for assessing laboratories which are summarised below with further details available in Appendix B. Values should be considered alongside other information rather than in isolation.

Inadequate cytology

The percentage of samples reported as cytology inadequate

PPV - Positive Predictive Value

A performance indicator measuring the percentage of women referred with high-grade cytology or worse, whose biopsy is reported as CIN2 or worse.

APV - Abnormal Predictive Value

The percentage of samples reported as borderline or low grade that led to a referral and subsequent histological diagnosis of CIN2 or worse.


Indicators

Referral value (RV) is also used when reviewing laboratory performance, but it is not a programme standard.

RV is the number of women referred to colposcopy per detection of one CIN2 or worse legion (excluding inadequate referrals).


For standards, when a laboratory is outside the 5th to 95th percentile range (see table below) this may require further investigation.

The 5th to 95th range for RV is also provided in the table below. Although no longer a standard, RV is still used by the programme for quality assurance purposes.

  5th - 95th percentile range Number of laboratories
within range in 2019-20
Standard or Indicator 2018-19 2019-20
Positive Predictive Value (PPV) for CIN2 or worse* 76.2 - 92.5% 76.6 - 91.6% 44 of 48
Referral Value (RV) for CIN2 or worse* 2.1 - 4.0 2.1 - 4.4 44 of 48
Abnormal Predictive Value (APV) for CIN2 or worse* 8.2 - 25.5% 7.0 - 22.9% 44 of 48
Number of laboratories whose results were
used to calculate PPV/RV/APV
49 48 n/a
Inadequate as a % of all samples** 1.0 - 4.2% 0.3 - 4.7% 41 of 45
Number of laboratories whose results were
used to calculate % inadequate
48 45 n/a

* The percentile ranges for the PPV, RV and APV indicators are calculated using data from the previous year (KC61, Part C2). For example, the PPV for 2019-20 is based on data from 2018-19.
See Appendix B for definitions of PPV, RV and APV and see Appendix E on Outcomes of Gynaecological Referrals for further information about cervical intra-epithelial neoplasia (CIN).
** Based on results for women aged 25 to 64 tested in GP and NHS community clinics only.
NB: Women with negative cytology but who test positive for HPV and are referred to colposcopy are not currently included in the calculation of referral value. See Appendix B – Definitions for more information.
Source: KC61, NHS Digital. See Data Tables 19 and 19a


Last edited: 8 July 2021 5:32 pm