Introduction An unexpected finding of abnormal liver function tests (ALFTs) is common in primary care. Currently there is a lack of data for determining the severity of liver disease, in particular nonalcoholic fatty liver disease (NAFLD), in the primary care setting.

Aim To determine the causes of unexpected ALFTs in a large primary care cohort. To determine the prevalence and severity of NAFLD in this cohort.

Method We analysed patients presenting with ALFTs, in the absence of known liver disease, to 8 primary care practices in Birmingham between 2006 and 2008. NAFLD was diagnosed in subjects with fatty liver on ultrasound (USS), negative liver aetiology screen, and alcohol consumption of =21 & =14 units/week in males and females, respectively. As a sub-study we calculated the NAFLD Fibrosis Score (NFS) (Angulo, Hepatology 2007) to estimate the presence of advanced liver fibrosis (F3/F4 Kleiner classification) in subjects who met the diagnostic criteria for NAFLD.

Results Data from 1118 adult patients were analysed: 56% male; 83.9% white race; Age 60 years (48–70); 23.5% type 2 diabetes; 52.2% hypertension; body mass index 28.7 kg/m² (25.5–33.1) (values expressed as median (IQR) or %). Regarding alcohol consumption, 42.5% were non-drinkers, 32.2% drank within UK guidelines (male=21, female=14 units/week) and 26.3% drank in excess.

Liver aetiologies identified included alcohol-induced liver disease (25.7%), haemochromatosis/carrier (1.1%), viral hepatitis B/C (0.91%), primary biliary cirrhosis (0.8%), alpha-1-antitryspin deficiency (0.18%) and primary sclerosing cholangitis (0.18%). Aetiology remained unexplained (normal USS, negative liver aetiology screen and alcohol consumption within UK guidelines) in 479 subjects, although at least 18% of this group had 2+ factors of the metabolic syndrome.

NAFLD was diagnosed in 26.4% (295/1118) of cases. A high NFS (>0.676) was found in 7.6% of these cases indicating the presence of advanced liver fibrosis. The presence of advanced fibrosis could not be confidently excluded in 35.2% of NAFLD patients who had an “indeterminate” NFS (−1.455 to 0.676), indicating the need for further investigation. Although NFS was validated in a secondary care cohort and may over-read severity in primary care, it is currently the best validated non-invasive method of assessing liver fibrosis in patients with NAFLD.

Conclusion NAFLD accounts for over a quarter of patients with ALFTs in primary care (26.9%). Of the patients with NAFLD a significant proportion either have advanced fibrosis (7.6%) or require further investigation (35.2%). This highlights the growing burden of NAFLD, and the need for validated methods of assessing NAFLD disease severity in primary care.