Page 193 - Registrar Orientation Manual 2016

Reference:
Effective date:
2015
Expiry date:
2018
Page:
19 of 28
Title: Laboratory Testing Guidelines (DRAFT)
Type:
Clinical Guideline
Version:
01
Authorising initials:
TB testing ($50 per specimen)
TB testing costs $200,000 a year. It is important never to miss TB but tests should only be
requested in patients where TB is a possible diagnosis or in the screening of risk patients.
Virology
Viral studies can be very expensive:
 HIV nucleic acid is $460
 Hepatitis B nucleic acid is $194
 A respiratory viral screen is $143
Choosing Wisely only have this one specific recommendation on virological testing:
Don’t repeat the viral load in HCV unless on therapy.
The DHB Shared Services Laboratory Test Referral Guidelines have this on hepatitis testing:
 Clinicians should try to identify patients with raised LFTs due to chronic viral hepatitis,
 All HBsAg-positive pregnant women should have their HBV viral load measured,
 There is somewhat of a hiatus in treating HCV infection, pending the availability of newer agents, but all HCV PCR-positive patients should be referred to a specialist,
 Many HBsAg-positive patients are not being properly followed up or referred, and stand the risk of developing preventable liver disease.
The guidelines note regarding serological diagnosis:
Hepatitis A and E
These are the simplest to diagnose:
The IgM is almost always positive at the time the transaminases are raised.
The IgG is used to determine immunity, or show seroconversion if IgM results are inconclusive.
Hepatitis B
HBsAg is present in almost all actively infected persons with HBV and is the first test that should
be requested if HBV infection is suspected.
HBV surface antibody is a test that should really only be ordered for adults in occupational health settings, preferably within a few months of the final dose of vaccine: those who develop a clear response will be protected for life.
HBV e antigen predicts high titres of virus, but its absence does not exclude high viral loads, especially in adults who were infected in childhood.
HBV DNA measurement is an essential part of assessment and management
Note that we screen with HBsAg, anti-HBs and anti-HBc to reduce the need for repeat testing.
Hepatitis C
Anti-HCV antibody is present in almost all those infected with HCV, but depending on the age
and sex at acquisition, only 70-80% will have active viral replication.
A viral load test is needed to identify actively infected patients.
Like HIV, the antibodies are non-neutralising, ie do not control infection.
The emphasis in Hepatitis C management is to identify and refer patients with raised ALT who are keen to engage in treatment.