By Dr Ananya Mandal, MD
Hepatitis C seldom manifests with symptoms especially in the early stages. However, these individuals are capable of spreading the infection. This makes diagnosing the disease early vital.
Blood tests are available to check for this infection. Blood tests for screening for hepatitis C may be undertaken in the sexual health clinic, GUM (genitourinary medicine) clinic or drug treatment service as well.
Screening in persons at high risk
Screening for Hepatitis C on a regular basis is important for some persons at high risk. These individuals are:-
Current and previous injection drug abusers.
Those who have received blood transfusions before September 1991 or organ or tissue transplants before 1992 in UK when these were not tested for hepatitis C infection.
Persons receiving organ or tissue transplants or blood transfusions in countries where hepatitis C is common.
Sexual partners of those infected with hepatitis C.
Infants and children of mothers with hepatitis C.
Healthcare workers who have had accidental needle-stick injury or splash injury.
Persons who have had a tattoo or piercing at a place where equipment may not have been properly sterilised.
Blood tests for hepatitis C infection
The Antibody test or anti hepatitis C test
This test, simply put, detects if the person has ever been exposed to the hepatitis C virus.
When the body is exposed to an infective organism, it raises antibodies against it. Some antibodies acquired after an infection may last for years or may lie dormant until the person is infected again.
This is the principle behind most viral infections like chicken pox which usually do not recur after the person has developed antibodies against it.
The antibody test for hepatitis C detects presence of such proteins produced by the immune system to fight the virus. However, development of these antibodies against the infection may take some time – usually some months. Thus the test will not show a positive reaction for some months after infection.
If the antibody test is negative but the person still has symptoms, the test may be advised to be repeated again. If the test is positive it indicates infection. However, an earlier infection that has already been cleared by the blood will also show a positive result.
In addition positive anti-HCV IgM levels are found in 50-93% of patients with acute hepatitis C and in 50-70% of patients with chronic hepatitis C. Therefore, anti-HCV IgM cannot be used as a reliable marker of acute HCV infection. To confirm a current infection the PCR test is recommended.
The PCR test
The PCR test or the Polymerase Chain Reaction test is applied to detect the presence of the reproducing and multiplying virus hepatitis C in the body.
A positive test is reported as detectable and indicates the infection has progressed to a chronic (long-term) stage.
This test usually takes around two weeks to process. Genotyping and quantitative hepatitis C RNA tests are performed before treatment of patients.
Those with possible long term infection with hepatitis C are also prescribed other tests including:-
Liver function tests – these detect the extent of damage to the liver. Liver function tests measure certain enzymes and proteins in blood to detect adequate functioning of the liver. These include bilirubin, ALT, AST, alkaline phosphatase, prothrombin time, total protein, albumin, globulin etc. A liver biopsy may be advised in severe cases of liver cirrhosis, scarring or possible liver cancer.
Complete blood count, and coagulation studies
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)
Last Updated: Apr 26, 2013