Should Patients with Abnormal Liver Function Tests in Primary Care be Tested for Chronic Viral Hepatitis

David T Arnold; Louise M Bentham; Ruth P Jacob; Richard J Lilford; Alan J Girling

Disclosures

BMC Fam Pract 

In This Article

Background

Liver Function Tests are Ordered in Large Numbers in Primary Care

Liver function tests (LFTs) are comprised of a panel of five to eight analytes that are processed inexpensively in large batches. LFTs are one of the most commonly performed "blood tests" in primary care, such that in 2003 the laboratory at University Hospital Birmingham received 67,182 requests for LFTs from 83 General Practitioner (GP) practices, serving a population of 300,000 (Cramb R; Chemical Pathology Specialist).

Enigmatic Responses to Abnormal LFTs in Primary Care Settings

An abnormal LFT may signify a serious disease that can be identified only through further testing. These conditions include liver diseases, such as primary biliary cirrhosis (PBC), diseases of other organs such as Paget's disease of bone, and multi-organ diseases such as haemochromatosis. However, the majority of people with an abnormal LFT in primary care settings will not have any such previously undetected disease. They will have either no disease at all, or will be manifesting the effects of alcohol abuse or obesity. The doctor is likely to be aware, or at least suspicious, of these behaviours when ordering LFTs, but this does not exclude the presence of other diseases that may aggravate liver damage. There is thus a real question about which specific further tests, if any, a GP should order when an abnormal LFT result is obtained in a patient with non-specific symptoms, or as a result of routine testing. In some cases there may be a clear indication for further tests. For example, if the patient has a family history of haemochromatosis then their iron saturation should be measured. In some cases the pattern of LFT abnormality may suggest a diagnosis - for example, an isolated raised unconjugated bilirubin suggests Gilbert's disease, while a high blood level of alkaline phosphatase (ALP) is indicative of PBC. In most cases however, no unambiguous clinical indication for follow-on testing exists. The literature deals mostly with the pattern of abnormality given a diagnosis, rather than the probability of the various diagnoses given a pattern of abnormal LFTs. It is therefore not surprising that guidelines for GPs[1–5] confronted by an abnormal LFT in patients with non-specific symptoms or detected fortuitously are inconsistent, or that the way GPs respond has been found to be eclectic.[6] A point on which guidelines do agree is that the LFT panel should be repeated following an abnormal result.

Criteria for Selection of a Topic for Decision Analysis

If there is any particular previously unrecognised disease that a patient would wish to have excluded by further testing, then it will have the following features:

1. it is a serious disease;
2. it is treatable in the prodromal phase;
3. failure to identify the condition can lead to permanent damage;
4. it can be diagnosed with a high specificity by a familiar and inexpensive test;
5. it is among the more prevalent of the serious diseases;
6. it is not a condition such as alcohol misuse or obesity, which can be diagnosed from history and examination.

Viral Hepatitis

We discern that chronic viral hepatitis is the prime candidate based on the above criteria. It is a massive problem worldwide[7–9] and Table 1 shows that it is the most common of the specific liver diseases in the UK population after alcohol damage. Moreover, chronic viral hepatitis can be reliably confirmed or excluded by means of a relatively inexpensive blood test.[10,11] The disease has a prodromal period lasting many decades and is eminently treatable if caught early, thereby averting cirrhosis and liver cancer.[12,13]

The purpose of the decision analysis described here is to inform the selection of an efficient strategy for the diagnosis of chronic viral hepatitis. Such a strategy should optimise the trade-off between detection rate and cost.

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