If a person has contracted the hepatitis C virus, it takes a while for their body to produce enough antibodies so that a test can detect them. This time is known as the window period.
The hepatitis C (HCV) window period is usually 4–10 weeks from the time of exposure. After 6 months, most people will have developed enough antibodies for an HCV test to detect. In rare cases, however, antibodies can take up to 9 months to develop.
If a person has a test during this window period, a hepatitis C antibody test may return a negative result.
A different kind of blood test — the hepatitis C virus RNA (PCR) test — can detect the virus much sooner. It can identify whether a person has the infection 2–3 weeks after exposure.
In this article, we look at how the window period can affect the diagnosis of HCV, and when a person should consider having a test.
After exposure to HCV, it takes the body some time to recognize it as a virus and begin developing antibodies to fight the infection.
Antibodies are chemicals that the body releases in response to an infection. The body begins to release antibodies after it detects the virus particles called HCV RNA.
If a person has a test during the window period, they may receive an early negative result. They will need to repeat the test.
A person typically contracts the HCV virus through contact with the blood of someone who has the infection.
A person should consider testing if they have:
- been born to a mother with HCV
- shared drug-injecting equipment, such as needles and syringes
- used unsterilized medical equipment
- come into contact with blood during sex with someone who may have HCV
- had a needlestick injury
- received contaminated blood from an unscreened source
- shared razors or other personal items with someone who has HCV
- had a tattoo or piercing in an unregulated facility with low hygiene standards
- breastfed an infant with cracked and bleeding nipples
It is not possible to pass the HCV virus on through breast milk, food, water, hugging, kissing, or sharing food or drinks with a person who has the virus.
Transmission of HCV during oral sex is rare, but if one partner has HCV, it is advisable to use protection, such as a dental dam.
Who should have a test for hepatitis C?
In the United States, the Centers for Disease Control and Prevention (CDC) recommend that most adults over 18 years, and pregnant women undergo screening at least once.
A doctor may also recommend testing at least once for people who:
- have HIV
- have ever injected drugs or shared needles or other equipment, even if it was only once, a long time ago
- have had certain medical conditions or undergone transplants and other treatments in the past
- have had a needlestick or other injury while working in healthcare or public safety setting
- were born to a mother who had HCV
A healthcare professional may advise a person to have regular screening if they:
- currently inject drugs, and share needles and other equipment
- have specific medical conditions
People who have been in prison or have tattoos and piercings may require HCV testing, depending on the circumstances.
If a person thinks they have had exposure to someone who has HCV, they should speak to their doctor about screening.
To diagnose a hepatitis C infection, doctors use a hepatitis C antibody test, which is a blood test. The test must have the approval of the Food and Drug Administration (FDA).
The hepatitis C antibody can show if a person’s body has made any antibodies to HCV. If they have, this indicates that they have had the infection at some point in their lives.
Some people have the infection at some time, but their immune system eliminates the virus after a few months. In others, the body is unable to fight off the virus, leading to chronic hepatitis C infection. Many people will not experience any symptoms until the disease has progressed significantly.
A non-reactive or negative test result will generally indicate that a person does not have HCV. However, if the person has the test during the window period, they could receive inaccurate results.
If the person knows when exposure occurred, a doctor may recommend waiting a few weeks before repeating the test.
A reactive or positive result tells a doctor that the person has had an HCV infection at some point in their lives. The result indicates that their body has created antibodies to fight the virus.
However, this does not mean that a person still has active HCV. Even if their immune system has eliminated the virus, they will still have the antibodies.
Experts are still unsure how much immunity a person has if they have had and recovered from HCV. Some research suggests that having antibodies does not prevent a person from getting the infection again. However, having antibodies may offer some protection and may help the body eliminate the virus more effectively a second time.
If a person receives a positive antibody test, their doctor may recommend further testing.
A nucleic acid test for HCV ribonucleic acid (RNA) will show if an HCV infection is still present. This test measures the amount of the virus in the blood.
Blood tests and a liver biopsy may be necessary to determine the health of a person’s liver.
There are various strains of HCV, and each one responds to treatment differently. Testing can help a doctor identify the correct strain and determine the best treatment option.
Many people with HCV do not show symptoms, but some may experience the following after an initial infection:
- a fever
- loss of appetite
- nausea and vomiting
- abdominal pain
- urine that is darker than normal
- clay or gray-colored stool
- joint pain
- yellowing of the skin or whites of the eyes
A person with a long-term HCV infection may not show symptoms until liver damage occurs later in life.
The time between exposure to the virus and the first appearance of symptoms is the incubation period. Symptoms usually appear within 2–12 weeks, but many people never have symptoms.
Ways of reducing the risk of contracting or transmitting HCV include:
- avoiding the use of injectable drugs, except in a medical setting
- avoiding sharing needles, syringes, water, or other tools if injecting drugs
- avoiding sharing personal hygiene items, such as razors and toothbrushes
- following universal blood and bodily fluid precautions in healthcare settings
- using a condom during sex
- choosing a licensed operator and clean environment for body piercing, tattooing, or acupuncture
In 15–45% of people who have HCV, the virus will disappear without treatment within 6 months, according to the World Health Organization (WHO).
However, the remaining 55–85% will develop a chronic HCV infection that increases their risk of liver damage, liver cancer, and other complications.
There is currently no vaccine to protect a person from HCV, but antiviral medication can help treat the infection and reduce the risk of complications.
Early treatment, with a 3-month course of pills, can cure the infection in many cases.
Anyone who may have had exposure to HCV should speak to their doctor, who can advise them when to test.