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Screening for NAFLD in primary care: a preventative wonder or are we barking up the wrong tree?

The burden of chronic liver disease has a substantial health and economic burden within the UK. Chronic liver disease is the fifth most common cause of death in the UK and of those five, it is the only one with numbers that are rising. With this in mind, it would make sense that earlier detection of liver disease in primary care is key to improving outcomes and reducing costs.

NAFLD is the most common cause of abnormal liver function tests (LFTs) picked up in general practice. Large epidemiological studies have shown that only a subset of NAFLD patients progress to NASH and cirrhosis, therefore not every patient needs to be referred to secondary care.

So what can general practitioners (GPs) do to pick up and refer the correct patients? Several fibrosis severity scores exist but there is no global consensus guidelines on screening for fibrosis. Recommendations vary from a no-screening approach (AASLD/NICE) and a pathway which targets high-risk populations (EASL).

What tests are available?

US imaging is often described as the best and easiest imaging modality available to clinicians with regards to diagnosis. It has a sensitivity of 85%, but if hepatic steatosis is lower than 30% then the pickup rate is reduced. It also suffers from user dependence.

MRI is an alternative which is far more sensitive at detecting steatosis. However, it comes at a considerable financial and time cost. Some patients may be excluded from MRI imaging due to existing conditions (e.g. pacemaker). Regardless, MRI for the assessment of NAFLD is a growing field and several new programmes such as LiverMultiScan have been shown to offer a superior method of measuring liver steatosis.

Once NAFLD has been detected then the next step is to identify the severity. The fibrosis-4 score (FIB4) was originally designed to assess fibrosis in patients with hepatitis C however its validity was later studied on over 500 NAFLD patients. It uses routine laboratory tests and patient demographics to predict the presence of fibrosis. Its simplicity allows for an easy method for GPs to triage NAFLD patients and refer to secondary care if needed.

Enhanced Liver Fibrosis (ELF) testing is another blood test which looks at various markers to help predict fibrosis severity. Although it is recommended in some guidelines (NICE), it is not always used due to the cost and the fact that other parameters (such as those used in FIB4) are more readily available.

Transient elastography is another non-invasive method of evaluating fibrosis by using low-frequency elastic waves to assess hepatic stiffness. FibroScan offers good sensitivity and specificity and can be offered as a point-of-care test. Various studies have demonstrated its use as a community screening tool and it has been validated in several causes of liver disease.

Is it worth the cost?

One of the largest studies looking at cost-comparison analysis was done by Srivastava et al in July 2019. The principal findings showed that stratification of fibrosis resulted in significantly fewer referrals to secondary care.

FibroScan alone was the most effective test at detecting patients with advanced fibrosis. However, FIB4 and ELF testing delivered the biggest cost-benefit. Studies have shown that all the above tests allow for earlier detection of advanced fibrosis, creating more opportunity to slow progression and start any appropriate treatment.

Where do we go now?

Multiple modalities for screening and risk stratification exist for NAFLD which are both non-invasive and cost-effective. NAFLD is a multisystem disorder which has morbidity associated with the liver and several other systems including cardiovascular disease, diabetes, hyperlipidaemia and cancer.

Mounting evidence shows that non-invasive screening in primary care to detect advanced fibrosis provides a cost-effective model for appropriate referral and prevention of disease progression in NAFLD patients.

The next step would be a global consensus guideline.

 

Dr Michael Gomez is a Specialist Registrar in Gastroenterology at the Royal Berkshire Hospital, UK.

 

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