CASL Hepatology Fellowship

Who should be tested?

Any patient with clinical or laboratory evidence for either acute or chronic liver disease should be considered as possibly infected with HBV. Individuals engaged in high-risk activities such as intravenous drug use or high-risk sexual activity are at risk, as well as individuals exposed to blood by reason of their occupation.In addition being a member of a population with a high endemic rate of HBV is a risk factor for infection.

The diagnosis of HBV infection is based on the detection of HBsAg in serum.

All HBsAg-positive individuals require further detailed assessment. The objectives are to characterize the nature of the infection and the extent and severity of any underlying liver disease. Other objectives include identifying patients who may benefit from anti-viral treatment, early diagnosis and management of cirrhosis and its complications, timely detection of HBV-associated hepatocellular carcinoma, and immunization of contacts at risk.

Chronic hepatitis B – Initial Investigations

The laboratory tests needed in the initial assessment in all cases of chronic HBV infection are listed in table 2.

Table 2.Initial investigation of the hepatitis B carrier

Tests of liver inflammation	AST ALT
Liver function tests	Bilirubin
	Prothrombin time/INR
	Albumin
Viral serology	HBeAg/anti-HBe
	Anti-HCV
Other important tests	BUN or creatinine
	CBC and differential

Measurement of the aminotransferases provide a measure of ongoing inflammation, whereas the bilirubin, albumin and INR estimate liver function. Anemia, leukopenia or thrombocytopenia may indicate cirrhosis with portal hypertension. A positive HBeAg is associated with the continued presence of actively replicating HBV in the liver and detectable HBV DNA in the blood. Such patients are at risk for ongoing liver injury. Their blood and body fluids are highly infectious. Anti-HBe-positive patients may have much lower viral loads, which may be undetectable in blood by standard assays. These patients usually have little ongoing liver damage. Anti-HBe-positive patients may be infected with the so-called “pre-core” mutant, which does not produce HBeAg. These patients may have detectable HBV DNA and may develop progressive liver disease leading to cirrhosis, and therefore merit life-long observation.

In selected cases additional tests are needed. Anti-HCV should be requested in patients at high risk (IVDU, high risk sexual exposures, origin in countries of high HCV prevalence).For those at risk for hepatocellular carcinoma (long term and childhood infections, positive family history), and those in whom cirrhosis is suspected an ultrasound is strongly advised.

Chronic hepatitis B – Special Investigations

HBV DNA Assays

HBV DNA can be detected in serum by several commercially available methods (see later).Table 3 lists the current tests, their limits and ranges.

Table 3.Manufacturer’s reported dynamic ranges for HBV DNA assays

Method	Working range
Abbott Solution Hybridization Assay	1.6 to~800 pg/ml
Digene 1^st Generation Hybrid Capture Assay	5-2000 pg/ml (1.4x10⁶ –5.6x10⁸copies/ml)
Digene 2^nd Generation Hybrid Capture Assay Standard test Ultra-sensitive method	1.4x10⁵ – 1.7x10⁹ copies/ml 4.7x10³ – 5.6x10⁷ copies/ml
Chiron Quantiplex™ bDNA Assay	0.7 – 5000 Meq/ml (7x10⁵ – 5x10⁹ copies/ml)
Roche AMPLICOR™ HBV Monitor™ PCR Assay	1000 – 1x10⁷ copies/ml

There is poor inter-assay standardization so that quantification of HBV DNA when tested on different assays can vary by approximately 10 fold or more when testing the same specimen. There is also considerable intra-assay variation so that repeat testing of the same sample will result in a significant difference in results (coefficient of variation for bDNA assay is 10-20%, and for PCR assays is 20-40%).It is therefore important for the clinician to understand the type of assay methodology used, and its limitations, and that a consistent methodology be used for all assays.

HBV DNA testing should be limited to those patients being considered for treatment and to evaluate response to treatment. It is not indicated routinely in the evaluation of all HBsAg-positive patients.HBV DNA testing should be readily available to qualified practitioners regularly involved in the treatment of HBV.

Liver Biopsy

Biochemical or serological tests, including HBV DNA, cannot predict histopathology with adequate precision. Therefore liver biopsy may be required to determine the severity of permanent liver injury (fibrosis or cirrhosis). The biopsy appearances may help in choosing appropriate therapy.

Ancillary tests