Guidance

Sentinel Surveillance of Blood Borne Virus (SSBBV) testing: protocol

Published 13 June 2024

Sentinel Surveillance of Blood borne Virus (SSBBV) testing (‘the denominator study’ or ‘DENOM’) began as a pilot study in February 2002, primarily to collect data on hepatitis C testing in 8 participating sentinel laboratories in England. The data collected through this surveillance scheme has been invaluable in enhancing knowledge and understanding of hepatitis testing.

Data collected includes information on hepatitis A to E, HIV and human T-lymphotropic virus type 1 (HTLV) tests regardless of the result conducted at participating laboratories in England. There are 23 participating laboratories, accounting for approximately 40% of diagnostic testing. Information from sentinel surveillance is used to estimate diagnosed prevalence in those tested and enhance our knowledge and understanding of bloodborne virus testing, including who is being tested, from which service type and how this has changed over time.

Within the UK an estimated 210,000 persons are living with chronic hepatitis B, 62,600 with chronic hepatitis C, and an estimated 107,8000 persons are living with HIV (see hepatitis C in England and the UK, hepatitis B in England and HIV annual data tables). Persons with hepatitis are at increased risk of developing liver disease and liver cancer and viral hepatitis is a leading cause of death worldwide, surpassing mortality due to HIV, malaria and tuberculosis (TB).

Within the UK, the undiagnosed fraction remains high for all 3 infections, partially due to many of those at risk, for example:

• people who inject drugs (PWID)
• recent migrants
• gay, bisexual and other men who have sex with men (GBMSM)
• being socially marginalised or less likely to access traditional primary care settings, or both
• people who are unaware of their risk
• people who are concerned by the stigma attached to a diagnosis

Furthermore, structural barriers including lack of health professional awareness and streamlined care pathways also contribute to the proportion of individuals diagnosed late.

In 2016, the UK government signed up to the first World Health Organization (WHO) global health sector strategy for viral hepatitis, making the elimination of viral hepatitis as a public health threat and a Public Health England (now UKHSA) priority. The strategy has a final elimination target that countries need to meet by 2030. The data collected by the SSBBV testing helps monitor our progression towards the WHO impact targets and elimination goal.

SSBBV testing is of public health value as this data is used to:

• estimate diagnosed prevalence in individuals tested for hepatitis A to E, HIV and HTLV
• enhance our knowledge and understanding of BBV testing, who is being tested and from which service types
• identify trends in testing and positivity, determine changes and gaps in services
• identifying disease trends and inequalities in vulnerable populations
• monitor the control of infection within the population
• audit testing guidelines such as testing coverage in non-traditional services, or following the diagnosis of an HIV indicator condition
• indirectly monitor hepatitis C treatment and the cascade of care for viral hepatitis including long term health outcomes (for example mortality and liver cancer) for people with bloodborne viruses (through linkage to other routinely collected surveillance data sets)
• evaluate interventions across the patient care pathway to decrease the undiagnosed fraction, ensuring individuals are diagnosed and accessing the appropriate healthcare
• parameterise economic and mathematical infectious disease models for evaluating cost effectiveness of interventions and predicting the future burden of disease with different strategies

Ultimately, this data informs:

• commissioning
• policy
• healthcare practice
• healthcare resource planning and allocation
• the prevention, testing and diagnosis and treatment of BBV
• enhancing our knowledge of the burden of disease
• understanding populations at greater risk
• where individuals are being tested
• possible gaps in testing

Population

SSBBV collects data on tests undertaken at any of the participating sentinel laboratories across England regardless of test result (both positive and negative results) for any of the following tests:

• hepatitis C antibody
• hepatitis C antigen
• ribonucleic acid (RNA)
• polymerase chain reaction (PCR)
• hepatitis C genotype
• hepatitis B surface antigen
• core immunoglobulin M (IgM)
• core total antibody
• e antigen
• e antibody
• DNA result
• hepatitis A IgM antibody
• HIV antibody, subtype and avidity index
• HTLV test result
• hepatitis E virus (HEV) antibody
• hepatitis D virus (HDV) antibody

Reporting of both positive and negative test results

Reporting of a positive diagnostic test of hepatitis A, B, C, D and E falls under the Health Protection (Notification) Regulations 2010. Regulations place a statutory duty on all diagnostic laboratories that test human samples in England to notify UKHSA if they identify a notifiable causative agent. A causative agent is any virus, bacterium, fungus, parasitic agent or microorganism, which is directly or indirectly responsible for causing the corresponding disease. The current list of notifiable causative agents can be found in Schedule 2 of the regulations.

The collection of negative test results enhances our understanding of the burden of hepatitis through:

• better understanding of testing trends, for example, signalling when an apparent increase in disease is actually being caused by an increase in testing, or is a decrease due to prevention and intervention activities or if testing has stopped
• better understanding of disparities in healthcare access to enable UKHSA to determine who is accessing testing, improving efforts to tackle disparities in access or healthcare diagnostic testing
• better understanding of whether recommendations and guidelines are being followed and in addition, which would allow optimisation of communication and targeting of diagnostic tests to individuals who need them

Reviewing the collection of BBV testing data

All surveillance activities and the collection of data, both personal and health specific information that is undertaken by UKHSA, is reviewed annually by a panel of information governance specialists in the UKHSA Caldicott Guardian Office. SSBBV has been assessed by the panel and has been deemed to be covered by Regulation 3 of The Health Service (Control of Patient Information) (COPI) Regulations 2002 to process patient identifiable information without consent and as part of Regulation 7 is reviewed annually. Further information on what information we collect, how we use it and who we may share it with are shared in the privacy notice.

When SSBBV was initially established the system was reviewed by the ethics committee and following this success it was adopted as part of routine surveillance without question from the National Research Ethics Committee.

Confidentiality Advisory Group (CAG) reference 

SSBBV does not have a CAG reference, as a CAG reference relates to Regulation 5 of COPI to set aside the common law duty of confidentiality to process data for medical research. SSBBV falls under Regulation 3 of COPI for communicable disease surveillance and is reviewed annually under Regulation 7 of COPI and not Regulation 5.

Regulation 3 COPI categories

The following categories that fall under Regulation 3 of COPI cover the purpose of SSBBV:

• diagnosing communicable diseases and other risks to public health
• recognising trends in such diseases and risks
• controlling and preventing the spread of such diseases and risks

Ethics

Ethical approval for SSBBV (known as ‘the denominator study’ or ‘DENOM’) was given by the Northern and Yorkshire National Research Ethics Service (NRES) (2001) and also by the Public Health Laboratory Service Ethics Committee (2002). Health Protection Agency (HPA) was the sponsoring body. In January 2010 a case was put to the Northern and Yorkshire NRES committee that as funding for the study had finished, this surveillance activity was now part of core HPA funding. A letter was received from the Chair of the committee agreeing that sentinel surveillance was now considered part of routine HPA surveillance activities and therefore no longer required.

Data processing

A minimum data set for all patients having hepatitis, HTLV or HIV tests in the participating laboratories is collected each month. All data is extracted by a named individual in each laboratory and is sent through to the sentinel surveillance team either by NHS email, or a secure web-based area called iGateway and run by UKHSA. iGateway is a secure system encrypted end to end and based on Microsoft .NET technology. The application is deployed in house behind the UKHSA Netscaler application. The data files transferred via iGateway are physically deleted after 30 days of upload and only users with the required level of access can download the files.

Once received the data is cleaned and reformatted to ensure consistency between sites. Patient’s surnames are encoded using the soundex algorithm. Duplicate patients are identified and flagged using combinations of NHS number, soundex code, date of birth and sex.

A soundex code is a letter and 3 numbers that represent the surname using a phonetic index. One  soundex code can represent multiple surnames and therefore creates a depersonalised code of the surname. You cannot identify a person’s surname from the soundex code.

The Patient Information Advisory Group approval was gained to retain patient names for follow-up of chronic infections as hepatitis is a causative agent notifiable to UKHSA under the Health Protection (Notification) Regulations 2010. Names of the positive individuals are retained to allow for look back exercises, to support reengagement and linking to established healthcare data sets. Individual names are not stored with the testing data and are removed and retained in a separate database for the purposes of follow-up or linkage.

Names of negative patients are removed once pseudonymised with a soundex and retaining the first name initial.

Patients are assigned a unique patient identification number (UPI) that links all tests performed for an individual. Clinical details are coded and place and setting of test are mapped appropriately.

Patient name, NHS number, date of birth and sex is extracted and run through the Personal Demographic Service to supplement where any information is missing and the match between the data is either 30 (NHS match) or 20 (name and date of birth match).

Ethnicity is not routinely available for patients, therefore ethnicity is supplemented using name analysis software Onomap which uses patient forename and surname to assign ethnicity using census data. Ethnicity is also supplemented using data reported through Hospital Episode Statistics (HES) where data is linked between the 2 data sets.

The data collated from laboratories are stored in 2 tables within an Oracle database. The 2 tables are the patient table which contains information about the patient, and the sample table which contains information on all tests conducted and the UPI links these 2 tables. The Oracle database is stored on UKHSA servers and is backed up regularly. Only named individuals have access to the processed data.

Data linkage projects use:

• laboratory number
• soundex code
• initial
• data of birth
• hospital number
• sexual health service number
• sex
• patient surname and forename
• NHS number

Data is linked to several established healthcare datasets including:

• TB surveillance
• HIV surveillance
• death registrations
• HES
• national drug and treatment monitoring system
• national cancer registry
• the transplant database

All linkage work has been reviewed against the Caldicott principles. 

Date of birth is used to calculate age at test, age at diagnosis and age at death.

Clinical information is used to determine risk factor information. Comments, clinical details and notes are used to code the following groups:

• injecting drug use
• risk
• review
• sex
• maternal
• contact
• review contact
• renal
• needle stick
• abroad
• antenatal
• fertility
• liver
• liver function tests
• symptoms
• screen confirmation
• study
• check
• other and unknown

Source of test request is used to group into one of the following:

• emergency department
• drug dependency unit
• general practice
• sexual health
• occupational health
• prison
• antenatal
• HIV
• in vitro fertilisation
• liver services
• renal services
• general medicine (outpatient or inpatient)
• other and unknown

Laboratories

The following is a list of laboratories currently reporting to SSBBV:

• Manchester Royal Infirmary
• Royal Preston Hospital, Lancashire
• Royal University Hospital, Liverpool
• Bristol Royal Infirmary
• North West London Pathology
• East London Pathology
• Kings College Hospital, London
• St Georges University Hospital, London
• Royal Sussex County Hospital, Brighton
• Eastbourne District General Hospital
• Freemans Hospital, Newcastle
• Hepatitis C Trust, London
• Find and Treat Team, London
• Addenbrookes Hospital, Cambridge
• Leeds General Infirmary
• Micropathology Ltd, Coventry
• Abbott Rapid Diagnostics (formerly Alere) , Oxford
• UKHSA Bloodborne Virus Reference Unit, London
• Diana Princess of Wales Hospital, Grimsby
• Heartlands Hospital, Birmingham
• St Thomas’ Hospital, London
• William Harvey Hospital, Ashford
• Queen Alexandra Hospital, Portsmouth
• NHS England (NHSE) testing register

Examples of how SSBBV data is used

Emergency department bloodborne virus opt-out testing: 12-month interim report 2023

UKHSA was commissioned by NHSE to conduct a public health evaluation of an NHSE funded programme of opt-out BBV testing within emergency departments. Data on both positive and negative tests are essential to be able to assess delivery of opt-out testing (the percentage of people who were tested) and the equity of delivery of testing, as well as in calculating test positivity to understand which populations were more likely to be diagnosed and newly diagnosed.

Hepatitis C and hepatitis B reports

UKHSA uses testing information to present the number of people testing in services and over time. This data is included within our routine reports for hepatitis C in England and the UK and hepatitis B in England and allows us to show the impact of interventions and the impact of testing practices, for example:

• decrease in test positivity: is this a true decrease or an increase in testing?
• introduction of an intervention to increase testing: has this worked and if so in what populations?
• has the test positivity remained stable; are not reaching the right populations?

Recent publications from the team

Collecting both positive and negative results also allows us to undertake research to help guide hepatitis elimination. UKHSA monitors recent infections of viral hepatitis using data on both negative and positive tests, by identifying people who test negative and then positive in a defined time frame. This data highlights populations at increased risk and supports ongoing work to identify gaps in the prevention of ongoing transmission (1). Similarly, having both positive and negative results and sequential tests for an individual has allowed us to understand hepatitis C reinfection in England (2) and the possibility of antenatal testing as a case-finding initiative for hepatitis C (3).

References

1. Leeman D, Simmons R, Mandal S, Desai M. ‘High risk of hepatitis C seroconversion amongst females with exposure to both prison and drug treatment in England’. International Network on Health and Hepatitis in Substance Users (INHSU) October 2023, pages 17 to 20

2. Hibbert, M, Simmons, R, Mandal, S, Sabin, CA, Desai, M. ‘Anti-Hepatitis C (HCV) test positivity and new HCV diagnoses among women tested in antenatal services in England between 2015 to 2019. Midwifery: December 2023, volume 127, page 103863

3. Hibbert, M, Simmons, R, Harris, H, Desai, M, Sabin, CA, Mandal, S. ‘Investigating rates and risk factors for hepatitis C virus reinfection in people receiving antiviral treatment in England’. Journal of Viral Hepatitis: August 2023, volume 8, pages 646 to 655

Appendix 1: Sentinal Surveillance of Blood Borne Virus (SSBBV) testing: minimum data set

The following items are downloaded from the laboratory information management system.

• laboratory number
• date of specimen
• soundex or code for pre-coded specimens
• date of birth
• hospital number
• sex
• source of request
• clinical details free text field
• clinician name
• patient surname and first name: names are run through the Nam Pehchan software to identify people of South Asian ethnicity (then deleted for negatives)
• NHS number
• ethnic group, if stored in the laboratory system

Test results (where available) include:

• hepatitis C antibody enzyme-linked immunosorbent assay (ELISA) result
• hepatitis C ribonucleic acid (RNA) polymerase chain reaction (PCR) result
• hepatitis C RNA PCR quantitative result (copies per millilitre (ml))
• hepatitis C genotype
• hepatitis C antigen result
• hepatitis B surface antigen ELISA result
• hepatitis B core core immunoglobulin M (IgM) antibody ELISA result
• hepatitis B core total antibody ELISA result
• hepatitis B e antigen ELISA result
• hepatitis B e antibody ELISA result
• hepatitis B DNA quantitative result (copies per ml)
• hepatitis B core IgM antibody quantitative result (copies per ml)
• hepatitis A IgM antibody
• hepatitis C and hepatitis B comments fields (contain additional information supplied by the laboratory and used for interpreting test results)
• sample type (to identify dried blood spot samples)

With the addition of HIV testing:

• HIV-1 and HIV-2  test result
• HIV subtype
• Recent Infection Testing Algorithm avidity index

With the addition of HTLV testing:

• HTLV types 1 and 2  test result

With the addition of hepatitis E virus (HEV) and hepatitis D virus (HDV):

• HEV antibody result
• HDV antibody result