Blood borne viruses (BBVs) like hepatitis B, hepatitis C and HIV are a serious public health concern, and with the advent of effective antiviral treatments for all three viruses, diagnostic tests that allow accurate and prompt detection and effective monitoring of these viruses are important contributors to patient management and wellbeing, and public safety.
South West London Pathology (SWLP) has developed an innovative solution to blood borne screening using capillary blood testing. The test has been developed by consultant virologist Dr David Carrington (St George’s University Hospitals NHS Foundation Trust) and biomedical scientists at SWLP and offers a number of advantages over the dried blood spot (DBS) testing method, which has traditionally been used to test for BBVs in the community setting.
It is particularly useful for those patients who are difficult to bleed and those patients attending outreach clinics were phlebotomy is not always available. The patient or healthcare assistant lances a finger-tip and collects 250 µL of capillary blood directly into a paediatric EDTA tube. They then recap and shake the tube to prevent clotting. The sample is stable for three days, although we recommend prompt delivery to SWLP to avoid sample degradation, which suports rapid testing and result turnaround.
The capillary blood test can detect HBsAg, HIV 1&2 anitgen/antibody and HCV antibody without loss of sensitivity or reduced specificity (compared to venepuncture samples) and in a parallel work stream allows quantitative HCV RNA on all patient samples (although it is possible to substitute HCV RNA for HBV DNA or HIV RNA testing – lower limit of detection is ~500 iu/ml). All positive HCV RNA samples undergo reflex HCV genotyping, which allows clinicians to select the most appropriate antiviral treatment combination.
The combination of both serological and molecular testing from one sample, on fully automated and verified equipment and assays, means that a further confirmatory test is usually unnecessary. The turnaround time for the test is four working days.
SWLP has been working closely with the Hepatitis C Operational Delivery Networks (ODNs), which are the new structures through which hepatitis C treatment is supplied in England. The Hepatitis C ODNs have used the new test in the opt-out testing at HMP Wandsworth and SWLP processes over 500 samples per month from this centre alone. The advantage of using this new type of test in this setting is that patients can be tested and, if positive, treated more quickly than using the dried blood spot test.
Dr Dan Forton, Consultant Hepatologist at St George’s Hospital, who leads the Hepatitis C OPN for south west London, says, “Provision of a CBT sample is straightforward and equivalent to, if not more simple, than a DBS sample. The sensitivity is equivalent to venous sampling – something which is not always true of DBS”.
SWLP Head of Operations Jamie Laughlin says, “The introduction of capillary blood testing for BBVs brings real advantages for patients and we are excited to be working with the Hepatitis C Operational Delivery Networks using the new methodology. We are already seeing an improvement in patient care in the speed with which patients can be diagnosed and treated appropriately.”
If you are interested in finding out more about this test or partnering with SWLP please email SWLPBusinessDevelopment@stgeorges.nhs.uk.
