Can routine blood tests be modelled to detect advanced liver disease in the community: model derivation and validation using UK primary and secondary care data

Algorithms for Early Detection of Silent Liver Fibrosis in the Primary Care Setting

More than one-third of the adult world population has steatotic liver disease (SLD), with a few percent of individuals developing cirrhosis after decades of silent liver fibrosis accumulation. Lack of systematic early detection causes most patients to be diagnosed late, after decompensation, when treatment has limited effect and survival is poor. Unfortunately, no isolated screening test in primary care can sufficiently predict advanced fibrosis from SLD. Recent efforts, therefore, combine several parameters into screening algorithms, to increase diagnostic accuracy. Besides patient selection, for example, by specific characteristics, algorithms include nonpatented or patented blood tests and liver stiffness measurements using elastography-based techniques. Algorithms can be composed as a set of sequential tests, as recommended by most guidelines on primary care pathways. Future use of algorithms that are easy to interpret, cheap, and semiautomatic will improve the management of patients with SLD, to the benefit of global health care systems.

Algorithms for early detection of silent liver fibrosis in the primary care setting - a scoping review

INTRODUCTION

Fatty liver disease affects almost 30% of the adult population worldwide. Most patients are asymptomatic, and there is not a linear relationship between exposure to risk factors and the risk of developing fibrosis. The combination of a very large, asymptomatic risk population where only a few percent will develop life-threatening liver disease is a growing diagnostic challenge for the health services. Accurate fibrosis assessment in primary care is limited by poor correlation with liver blood tests and low availability of elastography. Non-invasive tests are promising tools, but little is known about their diagnostic accuracy in low-risk populations.

AREAS COVERED

A scoping review was conducted to identify articles that focused on the current use of biomarkers and algorithms in primary care for the detection of patients with fatty liver disease in need of referral for further work-up.

EXPERT OPINION

Currently available algorithms for targeted screening for liver fibrosis perform better than the individual routine liver blood tests or liver ultrasonography. However, primary care physicians urgently need algorithms with even higher diagnostic accuracies than what is available today. The main limitation of the existing widely accessible algorithms, such as the FIB-4, is the large number of false-positive tests, resulting in overdiagnosis and futile referrals to secondary care.

Liver blood marker testing in UK primary care: a UK wide cohort study, 2004-2016

OBJECTIVE

We aimed to determine (1) the temporal trends of liver enzyme testing in UK general practice and (2) how these vary among different subgroups at risk of chronic liver disease (CLD).

DESIGN

Retrospective cohort study.

SETTING

UK primary care database (Clinical Practice Research Datalink (CPRD)), 2004-2016.

PARTICIPANTS

Patients aged 18 years or over, registered in the CPRD from 1 January 2004 to 31 December 2016.

OUTCOME MEASURES

The frequency of testing recorded within the study period in general practice was calculated for: alanine aminotransferase (ALT); aspartate aminotransferase (AST); gamma glutamyl transferase (GGT); alkaline phosphatase (ALP); bilirubin and platelets. Analyses were conducted in subgroups of patients at high risk of developing liver disease.

RESULTS

The study cohort included 2 912 066 individuals with median follow-up of 3.2 years. The proportion of patients with at least one measurement for ALT, ALP, bilirubin or platelet test gradually increased over the course of the study period and fell for AST and GGT. By 2016, the proportion of the population receiving one of more tests in that year was: platelet count 28.0%, ALP 26.2%, bilirubin 25.6%, ALT 23.7%, GGT 5.1% and AST 2.2%. Those patients with risk factors for CLD had higher proportions receiving liver marker assessments than those without risk factors.

CONCLUSIONS

The striking finding that AST is now only measured in a fraction of the population has significant implications for routine guidance which frequently expects it. A more nuanced approach where non-invasive markers are targeted towards individuals with risk factors for CLD may be a solution.

Performance of routine risk scores for predicting cirrhosis-related morbidity in the community

BACKGROUND & AIMS

Models predicting an individual's 10-year risk of cirrhosis complications have not been developed for a community setting. Our objectives were to assess the performance of existing risk scores - both with and without genetic data - for predicting cirrhosis complications in the community.

METHODS

We used a 2-stage study design. In stage 1, a systematic review was conducted to identify risk scores derived from routine liver blood tests that have demonstrated prior ability to predict cirrhosis-related complication events. Risk scores identified from stage 1 were tested in a UK Biobank subgroup, comprising participants with a risk factor for chronic liver disease (stage 2). Cirrhosis complications were defined as hospitalisation for liver cirrhosis or presentation with hepatocellular carcinoma. Discrimination of risk scores with and without genetic data was assessed using the Wolbers C-index, Harrell's adequacy index, and cumulative incidence curves.

RESULTS

Twenty risk scores were identified from the stage-1 systematic review. For stage-2, 197,509 UK biobank participants were selected. The cumulative incidence of cirrhosis complications at 10 years was 0.58%; 95% CI 0.54-0.61 (1,110 events). The top performing risk scores were aspartate aminotransferase-to-platelet ratio index (APRI: C-index 0.804; 95% CI 0.788-0.820) and fibrosis-4 index (FIB-4: C-index 0.780; 95% CI 0.764-0.795). The 10-year cumulative incidences of cirrhosis complications for participants with an APRI score exceeding the 90^th, 95^th and 99^th percentile were 3.30%, 5.42% and 14.83%, respectively. Inclusion of established genetic risk loci associated with cirrhosis added <5% of new prognostic information to the APRI score and improved the C-index only minimally (i.e. from 0.804 to 0.809).

CONCLUSIONS

Accessible risk scores derived from routine blood tests (particularly APRI and FIB-4) can be repurposed to estimate 10-year risk of cirrhosis morbidity in the community. Genetic data improves performance only minimally.

LAY SUMMARY

New approaches are needed in community settings to reduce the late diagnosis of chronic liver disease. Thus, in a community cohort, we assessed the ability of 20 routine risk scores to predict 10-year risk of cirrhosis-related complications. We show that 2 routine risk scores in particular - "APRI" and "FIB-4" - could be repurposed to estimate an individual's 10-year risk of cirrhosis-related morbidity. Adding genetic risk factor information to these scores only modestly improved performance.

Trends in indirect liver function marker testing in Wales from 2000 to 2017 and their association with age and sex: an observational study

Objective

If non-invasive markers of liver fibrosis were recorded frequently enough in clinical practice, it might be feasible to use them for opportunistic community screening for liver disease. We aimed to determine their current pattern of usage in the national primary care population in Wales.

Design

Using the Secure Anonymised Information Linkage (SAIL) Databank at Swansea University (2000–2017), we quantified the frequency of common liver blood tests (aspartate aminotransferase (AST), alanine aminotransferase (ALT), platelet count and albumin) used in fibrosis marker algorithms. We examined measurement variation by age and sex.

Results

During the 18-year study period, there were 2 145 178 adult patients with at least one blood test available for analysis. Over the study period, the percentage of SAIL patients receiving an ALT test in each year increased from 2% to 33%, with platelet count and albumin measurement increasing by a similar factor. AST testing, although initially rising, had decreased to 1% by the end of the study. AST and ALT values varied by age and sex, particularly in males with the upper normal range of ALT values decreasing rapidly from 90 U/L at age 30 to 45 U/L by age 80.

Conclusion

The reduction in AST testing to only 1% of the adult population limits the use of many non-invasive liver marker algorithms. To enable widespread screening, alternative algorithms for liver fibrosis that do not depend on AST should be developed. Liver fibrosis markers should be modified to include age-specific and sex-specific normal ranges.