Prevention the key

Blood banks have not felt the need to screen blood for the hepatitis family of viruses citing the cost of testing. It is significant that screening is to be made mandatory - a move that may be too late, says DR. SARANYA NARAYAN.

HEPATITIS C is an infection of the liver caused by an RNA virus, Hepatitis (HCV), that was discovered in 1989. It belongs to the family of flaviviruses. There are six distinct genotypes present and getting infected does not confer immunity against re- infection with the same or different genotype. Prior to its identification, all forms of post-transfusion hepatitis not due to Hepatitis A or B, were referred to as Non-A Non-B (NAHB) Hepatitis. Later, direct testing for Hepatitis C was introduced in blood banks in the United States in 1990, and by 1991 in the United Kingdom. It was then retrospectively identified to be the culprit in almost 50 per cent of post transfusion NANB Hepatitis.

"We stand at the precipice of a grave threat to our public health. It affects people from all walks of life, in every State, in every country. And unless we do something about it soon, it kill more people than AIDS," said C. Everest Koop, former U.S. Surgeon General, about the infection. These words are ominous for it is estimated that 200 million people around the world are infected with Hepatitis C, with more than 4.5 million cases in the U.S. alone. Statistics such as these are non-existent for India. Until now, the reason cited has been the cost of testing, because of which blood banks have not felt the need to screen blood for HCV. It is significant that from July, more than a decade after its discovery, screening of donated blood for Hepatitis C is likely to be made mandatory. The only fear is that it may already be too late.

Hepatitis C spreads through contact with infected blood. The way infection is spread is predominantly parenteral, in any of these ways:

(i) blood transfusion, (ii) organ transplantation, (iii) intra- venuous drug addiction and sharing of needles, (iv) kidney dialysis with the possibility of sharing contaminated supplies or equipment, (v) accidental needle-stick injuries, (vi) the process of delivery when an infected mother's blood can infect the newborn, (vii) sharing of razors or toothbrushes and (viii) unprotected sexual contact with an infected person. In half these cases, the source of infection is unknown. Hepatitis viruses are far easier to transmit and a much smaller volume of blood is sufficient to cause an infection (Table 1).

After an incubation period of between 40-120 days, the onset is insidious. Hepatitis C is usually a mild illness with only a slight elevation of liver enzymes. Jaundice occurs in a quarter of infected people while most are symptom free. However this in itself is a danger, as many who are completely unaware of their infected status progress to become carriers. This figure is currently estimated to be about 85 per cent of those who are HCV positive.

A look at the long term sequel of HCV infection, underlines why it is imperative that we need to screen blood donors for this virus. Of every 100 infected persons, 85 develop long-term infection, 70 develop chronic liver disease, 15 many develop cirrhosis over a period of 20-30 years and five may die of consequences of long-term infection (liver cancer or cirrhosis).

Diagnostic tools available:

There are few assays available, each useful in and for a specific situation:

To detect an antibody to the virus (anti-HCV), there are:

(a) Enzyme Immuno-Assay (EIA). The recommended screening test.

(b) Recombinant immunoblot assay (RIBA). A supplemental test that confirms the presence of the antibody.

As it is possible to get false positive results by EIA, it is imperative that any sample that tests positive by EIA is confirmed by a supplemental RIBA. A sample that tests negative in a person from a high risk group (a prior history of transfusion, organ transplantation or elevated ALT) needs to be re-tested every four or eight weeks, as the window period in HCV infection is fairly prolonged.

These two tests, however, do not reveal whether the infection is a recent or chronic one or whether the virus is still present in the blood or not. The simplest way of determining whether the disease is in an acute stage is by an estimation of the liver enzyme alanine aminotransferase (ALT). If this is elevated, we can assume that the disease process is still active. However, there are instances when even with an active infection, the ALT level does not increase. In such cases, it is prudent to monitor ALT levels every alternate month until it is certain that there are no fluctuations in the level, after which monitoring can be done less frequently. Most people who are exposed to the infection seroconvert within 12 or 14 weeks of exposure to the virus. Sometimes antibody tests remain negative repeatedly for as long as a year after exposure.

To detect the presence of virus (HCV RNA), there is:

(a) Polymerase chain reaction (PCR)-Qualitative. This test has been approved for testing donated blood and is already in use in the U.S. and the U.K. since last year. This is the ideal test for children less than a year old if a diagnosis needs to be made. Using this technique, the earliest it is possible to detect viral RNA is upto two weeks after exposure. At present there is no test that can identify a HCV infection earlier than this.

To detect the amount or quantify the virus (HCV RNA) there are:

(a) Polymerase Chain Reaction (PCR)-Quantitative

(b) Branched DNA technology (bDNA).

The most recently introduced test detects the presence of the viral antigen HCV Ag, and is being used in clinical trials in Europe at the moment. It is not available in India for diagnostic purposes.

Once the infection is confirmed, treatment is limited to Interferon, used either alone or in combination with Ribavarin. When used alone, Interferon is effective in 10-20 per cent of those infected. When used in combination, this figure increases to 30-40 per cent. Ribavarin is ineffective when used alone. A major drawback of interferon therapy is a worsening of liver disease in some individuals. In such situations the dose needs to be reduced or sometimes withdrawn completely. Interferon cannot be used during pregnancy. Other serious side-effects include thyroid disease, acute cardiac or renal failure, depression and hearing loss. Anaemia and congenital deformities are the major adverse effects of ribavarin usage and cannot be used in people with underlying renal disorders or during pregnancy respectively. Antivirals are usually not advised for children less than 18 years.

The virus undergoes sequence variation during the course of chronic infections and this mutagenicity is the chief reason for a vaccine not yet being available.

These figures show the magnitude of the problem (Table 2).

Protecting oneself from possible sources of infection would be wise and there are several ways to do this.

(a) Never shoot drugs intravenuously. If this is not possible, never share needles or syringes.

(b) Avoid sharing toothbrushes, razors or other personal products.

(c) Healthcare workers should follow routine barrier precautions.

(d) Avoid tattooing, tonsure, ear piercing or body piercing if the methods followed are not safe and hygienic.

(e) Avoid unprotected sexual encounters with people who are positive for the virus.

Given the inherent and unique qualities of the Hepatitis C virus - asymptomatic initial infection, mutagenicity and chronicity, together with the lack of a vaccine - prevention is possibly the only and most simple way to contain it.

The writer is Director, Jeevan Blood Bank and Research Centre, Chennai.

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