In medicine, the window period for a test designed to detect a specific disease (particularly infectious disease) is the time between first infection and when the test can reliably detect that infection. In antibody-based testing, the window period is dependent on the time taken for seroconversion.
The window period is important to epidemiology and safe sex strategies, and in blood and organ donation, because during this time, an infected person or animal cannot be detected as infected but may still be able to infect others. For this reason, the most effective disease-prevention strategies combine testing with a waiting period longer than the test's window period.
- HIV: The window period for HIV may be up to three months, depending on the test method and other factors. RNA based HIV tests has the lowest window period. Modern and accurate testing abilities can cut this period to 25 days, 16 days, or even as low as 12 days, again, depending on the type of test and the quality of its administration and interpretation.
- Hepatitis B: During the window period (or equivalence zone) of hepatitis B, both serological markers HBsAg (Hepatitis B surface antigen) and Anti-HBs (antibody against HBsAg) are negative (which is because, although Anti-HBs are present, they are actively bound to the HBsAg).In other words, the window period is the time interval between the disappearance of the HBsAg and the appearance of Anti-HBs(in terms of detecting them in the serum). Other serological markers, IgM (antibody) against HBc can be positive at this point.
- Incubation period, the time between infection and the appearance of symptoms
- "HIV/AIDS Facts". Centers for Disease Control and Prevention. Retrieved 15 June 2014.
- "HIV Test Window Periods". San Francisco AIDS Foundation. Retrieved 15 June 2014.
- p. 168, "Hepatitis serologic markers", Le, Tao, Bhushan, Vikas, Rao Deepak (2008). First Aid for the USMLE STEP 1. New York: McGraw Hill Medical. ISBN 978-0-07-149868-5. ; p. 1943, Harrison's Principles of Internal Medicine, 17th ed.