I can feel it in my bones--a case of deranged 'liver' function?

A 55-year-old Asian man was referred to a gastroenterology clinic by his general practitioner following an incidental finding of raised alkaline phosphatase (ALP) on routine blood testing. His ALP was found to be 198 (NR 35-129) with otherwise normal liver function tests. His past medical history consists of essential hypertension, type 2 diabetes and ischaemic heart disease. He was asymptomatic except for an intermittent ache over his left clavicle, which he had put down to angina. His gamma glutamyltransferase (GGT) was normal at 33 (NR 11-50) making bone the most likely source of his raised ALP. Imaging, including x-ray, CT and bone scan, showed an area of abnormality in the left clavicle. The appearances were consistent with fibrous dysplasia. We discuss the interpretation and investigation of deranged 'liver' function tests and suggest a rational and cost-effective diagnostic path to follow.