Blood-borne Viruses Testing and Laboratory Guidelines
What are blood-borne viruses (BBV)?
What is the transmission risk of BBV following occupational exposure?
Who is the source patient / health care worker (HCW) donor?
Who is the staff member / patient recipient?
What are the types of inoculations/ exposure incidents?
Do all inoculations carry the same infection risk?
Why is testing for BBV important?
Which are the best tests to track BBVs infection?
What is the role of HCV/HBV/HIV antibody test?
What is nucleic acid testing (NAT)?
What is viral load?
What is genotyping?
What is sequencing?
What are liver enzyme tests?
Why develop laboratory guidelines?
How to prevent blood exposure incidents?
Download Blood-borne Viruses Guidelines
These are viruses which some people carry in their blood and which may cause severe disease in some people and few or no symptoms in others.
The main blood-borne viruses are HBV, HCV and HIV.
• Hepatitis B Virus (HBV): Can be prevented through vaccination. HBV causes hepatitis (inflammation of the liver) and can also cause long-term liver damage.
• Hepatitis C Virus (HCV): Can cause long-lasting infection and can lead to carcinoma (cancer) of the liver.
• Human Immuno-deficiency Virus (HIV): Causes Acquired Immune Deficiency Syndrome (AIDS). HIV destroys the body’s ability to fight infection by attacking the immune system. This results in infected individuals becoming susceptible to opportunistic and potentially deadly, infections.
The estimated risk of transmission of BBVs following exposure is:
• Hepatitis B: 1:3
• Hepatitis C: 1:30
• HIV: 1:300
Acquisition risks from a positive source could be higher depending on the type of injury, the virulence and amount (viral load) of the strain from the source.
This is the person whose body fluid was involved in the exposure incident.
This is the staff or patient affected by the exposure.
Exposure occurs when body fluid from a donor/patient/HCW is inoculated or in contact with broken skin, mucous membrane or eyes of a recipient. The types of injuries that are associated with significant risks are:
• percutaneous – from needle, razors, bone fragments and human bites that break the skin
• mucous membranes – splash to eye/nose/mouth
• skin abrasion – scratches, cuts, eczema or any other condition of non-intact skin.
Some inoculation injuries carry a higher risk than others. For example:
• deep injuries caused by hollow bore needles
• injuries from a source patient/HCW who is infected with a BBV with a high viral load
• inoculations from needles that are visibly blood stained or have been in an artery or vein
• where the source patient is terminally ill with HIV infection.
The most common exposures are from percutaneous injuries and of these 63% are from hollow bore needles.
Laboratory tests can help to:
• detect if the recipient has been infected by a BBV virus
• detect the possible origin of the infection
• detect if the recipient has overcome the infection
• decide when to start treatment
• know whether or not the medication is working
• know if any of the medication is causing side-effects.
• Antibody Test
• Viral Load
• Liver Function Panel
This test reveals if a person has ever developed HCV/HBV/HIV antibodies, meaning whether or not he/she has ever been exposed to HCV, HBV or HIV.
‘Window period’ is the length of time after infection that it takes for a person to develop specific antibodies to be detected by current testing methods.
A positive antibody test does not necessarily mean an active HCV, HBV or HIV infection. It means that a “Confirmatory Test” is required to confirm a live, active HCV/HBV/HIV infection. For HCV alone, one out of four people clear the virus on their own. A negative antibody test means absence of HCV, HBV or HIV infection. False positives and false negatives are rare.
This is a screening test which detects the amount of viral RNA/DNA in the blood. This test is a marker of infectivity and confirms the results of the antibody tests. It shortens significantly the window period for diagnosis. After a BBV exposure the recipient can be antibody negative for several weeks because his/her body has not had sufficient time to develop antibodies. However NAT is able to detect viral RNA/DNA , which represents presence of the virus, rather than being dependent upon maturation of the recipient’s antibody response. This test is qualitative: Yes or no – you have it or you don’t. NAT assays are very sensitive (they can detect very small amount of viral RNA/DNA).
This test measures how much (quantitative) virus is in one millilitre of blood and it is expressed in “International Units per milliliter” (IU/ml).
It is used to determine:
• if there is replicating virus in a blood sample
• if treatment is likely to work for this person
• how the person is responding to treatment.
High numbers don’t mean high liver damage or higher immune-suppression, but does increase the risk of transmission.
The process by which a HCV, HBV or HIV strain is identified as belonging to a specific genetic group based on their genetic makeup and relatedness to prototype strains.
This test enables us to:
• distinguish contaminating from infecting strains
• document cross-infection among hospitalized patients or among patients and HCWs
• evaluate re-infection vs. relapse in patients being treated for an infection
• detect the development of specific antiviral resistant strains.
It is a technique used to determine the exact order of the base pairs in a segment of DNA/RNA.
This test enables us to:
• detect the genetic fingerprints of the infecting virus and ascertain the source of BBV transmission
• evaluate the genetic relatedness in a BBV cluster affecting several individuals who were potentially infected from a common source.
They are blood tests that tell us if the liver is inflamed (people with liver disease due to HBV or HCV infection should have this test done every six months).
There are two important liver enzyme tests:
• ALT: a test that is specific to the liver and measures inflammation, not scarring
• AST: levels can be affected by other organs, not just the liver. High values can mean acute damage to the liver. Inflammation could also be caused by medications, alcohol and other diseases.
Half of all people with severe liver damage have normal ALTs.
Because guidelines define procedures that ensure best practice in dealing with suspected cases of BBV transmission. The attached draft of the guidelines comprises the following sections:
• SECTION 1 – Principles for BBV cluster investigations
• SECTION 2 – Specimen handling, transport and storage
• SECTION 3 – Testing protocols for BBV investigations
• SECTION 4 – BBV genotyping and sequencing
• SECTION 5 – Laboratory requirements
Download Blood-borne Viruses Guidelines
Every effort must be made to avoid incidents occurring.
• Follow standard (universal) precautions.
• Do not re-sheath needles.
• Wear waterproof dressings over cuts and grazes.
• Use protective clothing as needed e.g. masks / goggles / gowns / gloves, if blood splash predicted.
• Dispose carefully of all ‘sharps’ at the point of use.