Reflex testing successfully uncovers hidden hepatitis C cases in Scotland

29 Jun 2021 Keith Alcorn
Originally published on www.infohep.org

Automatic viral hepatitis testing of blood samples from patients with abnormal liver function has the potential to identify “hard to reach” people with hepatitis B or C who have no known risk factors, an analysis of testing outcomes in the Tayside region of Scotland shows.

The procedure is an example of 'reflex' testing, in which blood samples automatically undergo other tests if they test positive for a condition or show results above a certain threshold.

The findings were presented to the International Liver Congress last week by Dr Callum Livingstone, a recent graduate of the University of Dundee School of Medicine.

Up to half of people with chronic hepatitis C in Scotland are estimated to be undiagnosed and remain at risk of liver disease progression without treatment.

Injecting drug use is the main risk factor for hepatitis C infection in Scotland and hepatitis C is highly concentrated in its most deprived neighbourhoods. People who inject drugs are likely to be offered hepatitis C testing during contact with drugs services or general practitioners, but people who are not known to have a history of injecting drug use are unlikely to be offered a test.

Although Tayside region, on Scotland’s east coast, has achieved the World Health Organization target for elimination of hepatitis C (diagnosing 90% of cases and treating 80% of diagnosed cases), people without known risk factors for hepatitis C may be missed.

In Tayside, any patient ALT result above 30 results in reflex testing of the sample for hepatitis B and C by the regional laboratory. The Intelligent Liver Function Test (iLFT) algorithm then uses laboratory test data and patient BMI and other medical history data to propose a diagnosis to the clinician who referred the patient for blood tests.

Tayside GPs like the system, Dr Livingstone told a question-and-answer session after his presentation, because it reduces workload and delivers test data and a diagnosis. Another evaluation of the system, not presented at the International Liver Congress, found that the diagnosis proposed by iLFT matched the diagnosis anticipated by the GP in 63% of cases.

Intelligent liver function testing combines elements of two good practices for hepatitis C elimination – electronic medical record reminders to test for hepatitis C and reflex testing – to improve detection of viral hepatitis and other liver diseases.

To evaluate whether intelligent liver function testing (iLFT) successfully detected patients with hepatitis C, Callum Livingstone carried out a retrospective study of patients in Tayside who triggered an iLFT order between August 2018 and August 2020.

During the study period, 6791 patients were referred for iLFT, of which 49 tested positive for hepatitis C antibodies. Twenty-nine had detectable HCV RNA levels and were invited for treatment. Twenty-eight patients began treatment, 26 completed treatment and 24 achieved a sustained virological response (four were lost to follow-up before confirmation of cure). Three of the patients cured of hepatitis C remained in care for follow-up of advanced liver disease, underlining the importance of detecting hepatitis C for prevention of liver disease progression.

The cases detected were untypical of Scottish hepatitis cases. Whereas the majority of people diagnosed with hepatitis C in Scotland are aged 30-39 years, the average age of people diagnosed through the iLFT screening system was 53 years. And although the majority of people diagnosed with hepatitis C in Scotland have a history of injecting drug use, 75% of those diagnosed as a result of iLFT said they had never injected drugs.

Finally, whereas half of people diagnosed with hepatitis C live in the most deprived neighbourhoods in Scotland, less than 15% of those diagnosed through iLFT lived in the most deprived neighbourhoods.

“iLFT identifies patients who do not have overt risk factors: those who do not inject drugs, are of an older age and live in more affluent areas,” said Dr Livingstone.