Guidance

NHS Cervical Screening Programme: laboratory quality control and assurance for human papillomavirus testing

Updated 25 August 2026

This document is for laboratories performing human papillomavirus (HPV) testing of clinician taken liquid-based cytology samples and self-testing samples for the NHS Cervical Screening Programme (NHSCSP). It provides guidance on procedures to support quality assurance in HPV testing and their monitoring including internal quality control (IQC) and external quality assessment (EQA).

This guidance was originally set up in response to queries received from laboratories in England and the UK that serve the cervical screening programme and was updated to include self-testing in preparation for the introduction of a self-testing offer for those who are underscreened in 2026. We recognise that only laboratories accredited to United Kingdom Accreditation Service (ISO 15189: 2022) will provide testing services to the programme. It is also recognised that local quality frameworks and quality management systems will be in place in laboratories that support the programme and that local obligations to such will apply.

1. Internal Quality Control (IQC) Material

In-house preparation of internal quality control material for HPV testing can be challenging for some laboratories. This may be due to the volume of residual material available after routine processing and/or a lack of access to proxies of clinical material.

This section provides guidance on IQC material and covers:

• sourcing
• preparation
• frequency of use
• monitoring
• expiry

1.1 IQC application, frequency and monitoring

The ISO standard does not stipulate frequency of IQC inclusion; however, it does state that the laboratory shall use quality control materials that react to the examining system as closely as possible to patient samples. Consequently, IQC should consider all sample types receipted by the laboratory where possible. Variation in the use of IQC is to be expected. It will depend on factors such as:

• sample types receipted by the laboratory
• HPV test throughput of the laboratory
• platform constraints or requirements
• local IQC practice for molecular testing that may cover multiple targets (including HPV)

It is common practice to include an IQC positive and an IQC negative sample with each machine batch of samples in addition to any mandatory manufacturer controls. However, as continuous loading platforms replace the batch type platforms, this way of operating may not be routinely feasible or relevant. Laboratories should include an IQC positive and negative sample every 24 hours as a minimum per instrument/assay for each sample type in use and, where possible, with each new kit lot or when changing the preservative-solution bottle used for the resuspension of self-taken samples.  Instruments record all lot numbers and by including a control every 24 hours the influence of lot changes can be assessed – such outputs can support with batch acceptance of reagents.

Laboratories should log and monitor IQC performance. Acceptability criteria for IQC pass or fail should be locally defined and the expected result should match the observed result at the qualitative level. A quantitative result is not currently relevant for management in the CSP. However, logging the numerical read-out of the assay (which will vary according to assay) using a Levey-Jennings chart is helpful in identifying assay-drift, and indicating any stability issues with the IQC.

There are several specific software systems that can monitor IQC performance and support the identification of issues and outliers. Irrespective of system imposed for acceptability, laboratories should log any breach along with a description of the subsequent corrective actions.

Where possible, the IQC material should be included in the associated pre-analytical system or manual front-end process so that the laboratory procedures are assessed end to end. It is accepted that this will be operationally more challenging for some platforms. Recourse to the platform manufacturer to support with options is advised. Even if it is not routinely feasible to include IQC during the pre-analytical phase, laboratories should monitor the quality of the pre-analytical system in some way.

Laboratories must label IQC material appropriately with the date it was prepared, if prepared in house and a relevant identifier which ensures linkage to the source material. IQC materials should be verified by the laboratory and any deviations from manufacturer’s recommendations for commercially obtained material should be validated.

A note on Uncertainty of Measurement (U of M)

The laboratory should describe how it measures uncertainty and justify/describe what level of uncertainty is acceptable. It is accepted that certain HPV assays which use quantitative PCR as a chemistry lend themselves to quantification of assay-drift and U of M more readily vs assays which work on other systems such as signal amplification and target mediated amplification. 

1.2 IQC derivation or preparation: examples, pros and cons

Pooled material from residual clinical samples and self-samples

Pooled, residual, anonymised cervical samples that generate consistent positive or negative results can be used for IQC purposes. Pooling samples is recommended to support the anonymisation process and to obviate the issues with potential inconsistency of results in single samples where the level of virus may be on the cut-off.  Pooled residual material from routine self-samples can be used, though lower residual volumes and fewer samples make this more challenging than with clinical samples. IQC for self-samples can be made by swirling dry swabs into pooled material (either clinical or self-samples) and processing them according to the self-sample workflow. The information below provides a high-level overview of the process that should be used if preparing pooled material, but for advice and specific protocols for preparing pooled IQC from residual screening samples contact the Screening Quality Assurance Service (SQAS).

1. Document associated results including date and type of testing.
2. Define and meet acceptability criteria before introducing into routine use. This may be aligned with local policy for molecular IQC. Note the criteria may be different between the pooled LBC and the self-testing swabs.
3. Anonymise each pooled sample.

Pros: mimics a clinical sample.
Cons: some laboratories may have platforms that limit access to sufficient residual material so generating working pools is more challenging.

HPV containing cell line material

Laboratories can order HPV containing cell lines such as HeLa, Caski and SiHa from centralised accredited culture collections such as American Type Culture Collection (ATCC). HPV negative C33a cell lines are also available, and laboratories may use these as negative controls.

Laboratories can use dilution of cell lines in cytological media for IQC material. However laboratories which are not co-located with culture facilities may not be able to store and propagate original material.

At the time of writing, the Scottish HPV Reference Library (SHPVRL) can provide pools of diluted cell-line material in preservative media to external laboratories. There is a charge/cost recovery for these samples to cover preparation and transit costs.

Contact SHPVRL for further details and advice on these materials, for example on availability,  handling and scope.  https://edinburghlabmed.co.uk/Specialities/reflab/hpv/

Pros: ability to standardise input, can be more stable than clinical samples.
Cons: less of a proxy for a clinical sample, lack of local culture facilities for propagation.

Non-NHS and commercial providers

Third party providers offer material that can be used for IQC purposes. The nature of the material ranges from lyophilised or freeze-dried specimens that require reconstitution to buffered liquid samples or dry FLOQSwabs which require resuspension in the laboratory according to self-testing workflow. Commercial material provides outputs at the “high risk HPV detected level”, the “high risk HPV not detected level” and the “HPV type specific level”.  The commercial material could feasibly be used to spike for example pooled negative clinical or self-sample material.   In the last 3 years the availability and range of HPV materials available from commercial providers has increased significantly.

Pros: Confidence in supply. Independent manufacture to standards relevant for the preparation of quality control material (for some). Additionally, some controls provide meteorological traceability
Cons: additional costs, dissimilarity to biological matrices (the extent of both will vary depending on the provider)

The matrix that some material is provided in may not reconcile with certain platforms. Laboratories must validate any manipulation of the commercially provided material outside the manufacturer’s instructions before the material is put into routine use.

A note on IQA

IQA is the selective retesting of a proportion of tested samples from the total workload.  Advice on the extent and nature of IQA was included in previous versions of this document.  However, in line with discussions of the laboratory technology group in addition to feedback from active service laboratories it is accepted that IQA is challenging to maintain and represents operational and governance challenges, particularly with tests that, while clinically validated, are not based on quantitative PCR.  Furthermore, IQA is more suited to diagnostic tests vs screening tests.   When considering the other quality monitoring activities obligatory for UKAS accreditation, some of which are covered in this document, the consensus of the laboratory technology group is that IQA is not mandatory for HPV laboratories that perform HPV screening.

2. Inter-laboratory schemes

Inter-laboratory schemes involve (usually reciprocal) exchange of samples between willing laboratories. Laboratories must log, check and assess concordance between expected and observed results and fully investigate and record any discrepancies.  While participation in an Inter laboratory scheme is not mandatory for UKAS purposes provided the laboratory is registered with an EQA provider, they can be useful for yearly verification exercises and to support with real-time troubleshooting and supportive communications between laboratories. Laboratories should ideally participate in inter-laboratory schemes that substantially fulfil the relevant requirements of ISO, however in the absence of these, creating local schemes is suitable.  Inter-laboratory schemes may help in the evaluation of pooled residual material relevant for the quality control of self-taken samples, given that at time of preparation of this document, self-sampling is a recent development to the programme.

3. External quality assessment

Laboratories providing HPV testing must participate in, and show adequate performance in, an externally accredited EQA scheme.

EQA schemes which offer an HPV panel include Quality Control for Molecular Diagnostics (QCMD) http://www.qcmd.org/ UK NEQAS https://ukneqasmicro.org.uk; other international schemes also exist. An overview of HPV quality materials and schemes is included in (1). Participation with a minimum of one EQA accredited scheme is mandatory, but laboratories may choose to participate in more than one given that they can provide complimentary and more frequent challenge(s).

Most existing EQA schemes that are externally accredited do not base scoring on type specific detection and rather base it on qualitative presence or absence of high-risk HPV types. At time of preparation of this document, the CSP do not use HPV type-specific results to trigger management decisions so this does not represent an issue as such.  Certain EQA schemes will provide type specific results, including for information purposes; for laboratories that house a platform that provides a type specific output, consideration of this information may help identify issues with analytical specificity. 

Laboratories should assess and document any performance issues with EQA and record any associated corrective actions – this is obligatory for accreditation purposes.

4. Validations

For clinician taken samples,

Laboratories must use an HPV test that has been formally accepted by the NHSCSP (see guidance on acceptable HPV tests); for a test to be added to the “accepted” list, centralised evaluation and validation has been performed through a comprehensive pathway according to: Cervical screening: pathway for acceptance of new HPV tests - GOV.UK (www.gov.uk)

Given the above, laboratories are not expected to perform extensive validations to confirm clinical sensitivity and specificity which would take several hundred samples. Laboratories are however required to confirm that the test is functioning operationally and analytically as expected in-situ and should perform technical validations in-house with the use of pre-annotated stored material and/or quality materials (external and, or internal) for each instrument/assay used in HPV testing.

Internal validation should include support where possible and available from the commercial provider. It is anticipated that the kits required to support validation will be supplied gratis by the manufacturers.

Before live use:

• the commercial provider will determine the success of installation using analytical checks and processes relevant to the platform and provide documentation to confirm this
• an analytical validation panel of 16 samples in triplicate (n=48) with known/anticipated results should be tested over 3 independent runs by 3 separate operator(s)

Samples within the panel may include:

• standard positive and negative control material associated with the assay/platform
• residual material from HPV EQA schemes
• HPV containing cell line material
• other independently sourced HPV control material (see section 1.2)

Additionally, SHPVRL can provide pre-annotated materials for quality control and validation purposes (where possible and where requested). These are managed on a case-by-case basis and cost-recovery for materials and courier costs are applied.

For self-taken samples

Only HPV tests that have been considered acceptable by the cervical screening programme for use on self-samples should be used. At time of preparation of this document this represents two platforms, based on the findings of the HPValidate project (2), however it is anticipated that this list may increase as a result of continued review developments and evidence, supported by the programme

A validation panel of samples with known outcomes should be assessed by all operators – a suggestion is as follows which

• To prepare self-samples using pooled control material as outlined in section 1.2, 10 positive and 10 negative samples should be created in advance by vortexing the pooled material for 10 seconds and thoroughly swirling the swab for 10 seconds into the control material. These self-samples must accurately reflect the types of swabs received by the laboratory. Each operator responsible for processing self-samples is required to handle 10 positive and 10 negative samples, arranging them in an alternating sequence (“pos,” “neg,” “pos,” “neg,” etc.) in a chequerboard pattern prior to testing. All pre-analytical procedures should closely replicate standard laboratory practices. The observed results must correspond with the expected outcomes at a rate of 100%.

• For swabs received in media, samples can similarly be prepared in advance by vortexing pooled material for 10 seconds and thoroughly swirling the swab into the control material before breaking it off into the designated media. Operators should prepare 10 positive and 10 negative samples, alternating their order in a chequerboard arrangement (“pos,” “neg,” “pos,” “neg,” etc.) before proceeding with testing. Pre-analytical steps should emulate anticipated routine workflows as closely as possible, including any required heating steps. Observed results must match expected outcomes with 100% accuracy.

Successful completion of the validation exercise may be included as evidence within a competency assessment document.

5. Verification including annual review of IQC and EQA performance

It is recommended that laboratories undertake yearly verification of HPV assays. Local templates for verification reports often incorporate a review of IQC and EQA performance as well as a summary of any operational or manufacturer issues. Laboratories must clearly state the method of verification and criteria used to demonstrate success. Ideally verification should be performed annually but if there have been significant changes (such as move of the equipment or major repairs) the influence of such should be determined through a verification to ensure the platform is performing as anticipated before being returned for service work.  Demonstration of success can be supported by testing materials used for IQC and also previous EQA panels.

6. Other aspects of laboratory practice to ensure quality in HPV testing

6.1 Environmental swabbing

Laboratories should document results of environmental swabbing and record any associated issues or actions.

Some of the HPV techniques used in the laboratory amplify microbial targets present in screening samples. This amplification may produce billions of copies of these targets, which pose a contamination risk. Laboratories should reduce the risk of contamination with daily cleaning of benches, computer keyboards, equipment, door handles and so on, using DNA denaturing agent.

It is good laboratory practice to carry out monthly environmental swabbing of the testing areas to ensure quality of results pre- and post- decontamination procedures. Negative results from environmental samples provide reassurance that the laboratory is free from amplicon (which could cause false positive results).

6.2 Reagents, consumables and verification

Laboratories should have documented procedures for the reception, storage, acceptance testing and inventory management for reagents and consumables in line with UKAS standards.   Laboratories should ideally verify each new reagent delivery prior to active use, using a defined and documented procedure. This ensures consistency of performance between batches - and that the change in reagent has had no impact on the quality of the examination. This said, it is understood that for certain platforms, prior/separate verification of reagents before active use may be challenging.  If prior verification is not possible, details of how the performance of new lots are assessed (e.g. monitoring of IQCs & kit controls), should be included in standard operating procedure(s)

6.3 Equipment calibration and metrological traceability

Laboratories must keep documented evidence of regular equipment servicing and calibration. The service report should be detailed enough to include tasks undertaken and results prior to handover, verifying the required measurement accuracy. If the supplier of the HPV platform maintains and services the equipment, laboratories should obtain calibration evidence from them.

Laboratories must regularly calibrate small equipment that is required for testing but not supplied by the manufacturer e.g. automated pipettes. They must have evidence of this, including a calibration certificate. Companies providing the calibrating and servicing must be compliant with ISO17024. 

Laboratories should, as standard, have a system for the monitoring of temperatures which accommodates the testing platform itself or associated reagents, compliant with UKAS standards. Data loggers and appropriate software(s) are commercially available.

6.4 Supplier (commercial) issues

A summary report of commercial supplier issues should be documented and formally reviewed by the local laboratory annually as a minimum.  This should detail any problems with response times for manufacturer repairs/maintenance and also periods of machine inactivity as a result of faults. Depending on the platform it is possible to quantify the number of technical (platform-driven) “errors” as a function of the software and this measurement can be included in the report

6.5 Interfacing between HPV assay platforms and the laboratory information management system (LIMS)

The laboratory should verify the electronic interfacs between the HPV platform and the LIMS. This ensures accurate transmission of results to service users. Further verification is required where a translation protocol or additional software (‘middleware’) is used to generate NHSCSP result codes from analyser HPV results.

7. Staff training and competency

The supplier must provide training on a new HPV platform to an appropriate core of staff who can then cascade training to existing and new staff.

The Screening Quality Assurance Service (SQAS) must be provided with evidence that:

• training is provided on site
• all staff undertaking testing have completed their training
• staff have a certificate of completed training

All staff receiving cascade training should be provided with training logs. These should include:

• evidence of competency (an assemblage of observation, assessments, verbal assessments, panels of anonymised previously tested samples)
• signatures of assessors with dates
• review and future re-assessment dates

If a laboratory decides to adopt more than one HPV testing method, staff must be trained to the required level of competence in each of the tests used. The laboratory should demonstrate comparability of results for patient samples to the same or different procedures, equipment, or different sites.

References

1: Cuschieri K, Fellner MD, Arroyo Mühr LS, Padalko E, Correa RM, Dillner J, Gultekin M, Picconi MA. Quality assurance in human papillomavirus testing for primary cervical screening. Int J Gynecol Cancer. 2023 May 1;33(5):802-811. doi: 10.1136/ijgc-2022-004197. PMID: 36914171; PMCID: PMC10176393.

2: Mathews CS, Sargent A, Cuschieri K, Rebolj M, Brentnall AR, Mackie A, Mills C, Martinelli C, Wright AM, Hunt K, Bird A, Patel H, Smith D, Johnson T, Ellis K, Hunt M, Denton K. HPValidate-human papillomavirus testing with DNA and mRNA assays on self-collected samples in cervical screening: comparison of test characteristics on three self-sampling devices. Br J Cancer. 2025 Sep;133(5):665-673. doi: 10.1038/s41416-025-03102-5. Epub 2025 Jul 8. PMID: 40629046; PMCID: PMC12405571.