Antibodies do not equal active infection
The rapid test detects antibodies to the hepatitis C virus, not the virus itself. This is a fundamental point that often causes anxiety and misunderstanding. Antibodies persist for life both in those who have suffered an infection and recovered on their own, and in those who have been successfully treated with modern antiviral drugs.
Therefore, a positive result means only one thing: contact with the virus has taken place. Only PCR for the RNA of the hepatitis C virus can determine whether there is an infection now. In approximately every fourth or fifth infected person, the virus is eliminated on its own, and such a person, having positive antibodies for life, is healthy and does not need treatment.
The opposite situation is also possible: in the first weeks after infection, antibodies have not yet been developed, and the rapid test will be negative in case of active infection. This serological window period can be up to two to three months. If there is a real risk of infection - contact with blood, use of non-sterile equipment - the correct approach is to study the RNA of the virus using the PCR method, and not wait for the appearance of antibodies.
How to read reference values
Each form contains a reference interval - a range of values typical for healthy people. It depends on the methodology and equipment of a particular laboratory, so it is incorrect to directly compare the results of different laboratories; To monitor over time, it is better to take tests in one place.
The reference interval covers most healthy people, but not all: a slight deviation may be an individual norm. Conversely, a value within the interval is sometimes a deviation for a particular person if he previously had different numbers.
What distorts the result
The most common causes of errors are not related to the laboratory, but to preparation. Eating changes the levels of glucose, lipids and a number of enzymes. Physical activity the day before increases creatine kinase and transaminases. Stress affects hormones and glucose.
The sampling technique is also important: prolonged application of a tourniquet increases potassium and protein fractions, and hemolysis of the sample makes several indicators unreliable. If the result is questionable, it is better to retake the test rather than start treatment immediately.
Express methods and their place
Express tests provide an answer in minutes and are indispensable where speed is important: upon admission to a hospital, before emergency surgery, when examining contact persons. Their sensitivity is lower than laboratory methods, so a positive result always requires confirmation.
A negative rapid test early after possible infection also does not exclude infection: during the serological window, antigens and antibodies have not yet reached detectable levels.