What is the window period for HIV testing?

The window period refers to the time after infection and before seroconversion, during which markers of infection (p24 antigen and antibodies) are still absent or too scarce to be detectable. Tests cannot always detect HIV infection during the window period.

All tests have a window period, which varies from test to test. It also depends on the specimen that is being tested: window periods are usually reported based on a sample of blood plasma, but are longer when the specimen tested is fingerprick blood or oral fluid.

(Plasma is the colourless fluid part of blood, separated from whole blood using laboratory equipment. Fingerprick blood is produced by pricking the finger with a lancet, whereas oral fluid is obtained by swabbing the gums.)

There are two key questions to ask about a specific HIV test: 

The information given in UK testing guidelines about window periods is based on answers to the second question – specifically, how long after exposure to HIV 99% of infections will be detected by a specific type of test. At this stage, it is highly likely that a negative result is accurate.

It is hard to say exactly how long the window period lasts, as there are variations between individuals and it is a difficult topic to research (recently infected people would need to know exactly when they were exposed to HIV and then give multiple blood samples over the following days and weeks).

Nonetheless, a study by Dr Kevin Delaney and colleagues calculated window periods for a range of HIV testing assays. All these analyses were based on plasma samples. Window periods are likely to be several days longer when testing samples of fingerprick blood or of oral fluid, as will be normal when using rapid, point-of-care tests and self-testing devices. Unfortunately, precise figures for how much longer the window periods are have not yet been published.

NAM aidsmap's Matthew Hodson explains about window periods for HIV testing.

The researchers’ analysis confirms that fourth-generation laboratory tests (which detect both antibodies and p24 antigen) detect HIV infections between one and three weeks earlier than older antibody-only tests. Moreover, their data suggest that some countries’ guidelines which recommend retesting 90 days after a possible exposure to HIV are more cautious than they need to be.

A fourth-generation laboratory test is recommended in UK and US guidelines. It uses a sample of blood plasma or serum and can detect immunoglobulin G (IgG) antibodies, immunoglobulin M (IgM) antibodies and p24 viral antigen (a protein contained in HIV's viral core that can be detected sooner than antibodies). Commonly used tests of this type include Abbott Architect HIV Ag/Ab, GS Combo Ag/Ab EIA and Siemens Combo HIV Ag-Ab.

UK guidelines state that 45 days is the window period for fourth-generation laboratory tests.

A fourth-generation rapid test is available (Determine HIV Early Detect or Determine HIV-1/2). While results for this assay when testing plasma were broadly similar to those of equivalent laboratory tests, the window period is likely to be several days longer when testing fingerprick blood, as the test is normally used.

A few third-generation rapid, point-of-care tests are available. They can detect immunoglobulin G (IgG) antibodies and immunoglobulin M (IgM) antibodies. Examples include the INSTI HIV-1/HIV-2 and Uni-Gold Recombigen HIV tests. The estimated window period for INSTI when testing plasma are as follows:

However, those estimates were based on testing plasma. In practice, tests are usually done on fingerprick blood and the window period is likely to be several days longer.

UK guidelines state that 90 days is the window period for all rapid, point-of-care tests.

Third-generation laboratory tests are no longer recommended for use. They can detect immunoglobulin G (IgG) antibodies and immunoglobulin M (IgM) antibodies, but not p24 viral antigen. Their window periods are similar to those of the INSTI third generation rapid test (plasma samples), but a little shorter (median 23 days).

UK guidelines state that 60 days is the window period for third-generation laboratory tests.

Many rapid, point-of-care tests are described as second generation. They can detect immunoglobulin G (IgG) antibodies, but not immunoglobulin M (IgM) antibodies or p24 viral antigen. As these two substances are detectable sooner after HIV infection than IgG antibodies, second-generation tests have longer window periods. Examples include OraQuick Advance Rapid HIV 1/2, Clearview HIV 1/2 STAT-PACK and SURE CHECK HIV 1/2.

However, those estimates were based on testing plasma. In practice, tests are usually done on fingerprick blood or oral fluid and the window period is likely to be several days longer.

UK guidelines state that 90 days is the window period for all rapid, point-of-care tests.

In HIV testing, the period of time after infection and before seroconversion during which markers of infection are still absent or too scarce to be detectable. All tests have a window period, the length of which depends on the marker of infection (HIV RNA, p24 antigen or HIV antibodies) and the specific test used. During the window period, a person can have a negative result on an HIV test despite having HIV.

A protein substance (immunoglobulin) produced by the immune system in response to a foreign organism. Many diagnostic tests for HIV detect the presence of antibodies to HIV in blood.

The fluid portion of the blood.

Another name for antibodies. An antibody is a protein substance produced by the immune system in response to a foreign organism (such as bacteria, virus or parasite).

A test in which all stages, including reading the result, can be conducted in a doctor’s office or a community setting, without specialised laboratory equipment. Sometimes also described as a rapid test.

No self-testing devices were included in this study. However, most self-tests are modified versions of rapid, point-of-care test kits that were originally designed for healthcare professionals. Most are based on second- generation tests, so are likely to have relatively long window periods. A few, including the INSTI HIV Self Test, are based on a third-generation test.

Similarly, self-sampling was not included. In the UK, this usually involve the user sending a sample of fingerprick blood to be tested in a laboratory with a fourth-generation antibody/antigen test. Plasma is extracted from the sample using centrifugation. In theory, the test will be as accurate with plasma from a self-collected sample of fingerprick blood as from venous blood, including in relation to acute (recent) infection.

In some situations, these figures should be interpreted with caution:

Standardized Test Policy

We don’t require applicants to submit standardized test scores because we think there are better ways to determine if you’ll be successful at Conn. And we want you to highlight your strengths in the application process, not write about a random topic we've assigned. We believe your high school transcript, essay, recommendations or other application materials may show your strengths better than test scores.

Our advice is to submit your scores if you feel they are representative of your achievement and will enhance your application. (Review the middle 50% range of scores submitted for the Class of 2024.) However, if you feel your standardized test scores do not reflect your full potential and elect not to submit them, you will not be at a disadvantage in the admission process.

In the Common App, simply choose which one testing score option you'd like us to consider:

If you would like us to consider your tests scores as part of your application, note that we accept both official and self-reported test scores.

Official test scores can be submitted in any of the following ways:

Self-reported test scores can be submitted in either of the following ways:

If you submit self-reported scores, please note that your official test scores will be required upon enrollment. Any discrepancies from self-reported test scores may result in rescinding our offer of admission.

We “superscore” the SAT Reasoning Test and use the combined highest composite score from the ACT. You should send scores from every SAT/ACT date for which you received your best scores in specific sections.

Scores from standardized tests taken through November typically arrive in time for Early Decision I consideration. Tests taken in December will arrive in time for Early Decision II and Regular Decision applicants.

Standardized test scores are not considered in the transfer application process.

Conn's standardized testing policy does not apply to testing for purposes of demonstrating English proficiency. Students whose first language is not English must submit the TOEFL, IELTS, Duolingo or PTE.

2021 Year in Review: Testing

Coming out of the COVID-19 pandemic, 2021 has been a year of acceleration and enhancements in the technology industry. In the testing space, we have seen a strong pull towards testing automation and the overall modernization of the way software teams conduct tests.

This year, financial services teams have felt this push towards automation and modernization of testing in response to increasing customer expectations. Back in January, an SD Times story showed that several financial services teams made the move to an open-source, technology-agnostic, test automation framework with the capability to span the entirety of the DevOps life cycle. 

The primary reasons financial services organizations found themselves flocking towards modernizing testing are the improvements in performance and efficiency that came as a result. It was reported that modernizing and automating testing led to a 10% improvement in developer efficiency as well as a significant improvement in application performance. 

Also in the testing space, in February of this year, BlazeMeter released BlazeData in order to make generating test data simpler. This allowed users of varying skill levels to quickly and synthetically generate data for any UI functional test. This came as a response to user demand for an easier way to create reliable test data.

This release provided many benefits to the developer community such as ease of use, not requiring specialized training to create test data, lower costs, and the ability to reuse the data once it’s been created. This release served as a one-stop shop solution in the marketplace for the users entire testing process. Months after this release, in October of this year, BlazeMeter was acquired by Perforce Software. 

Also in October of 2021, the UI testing framework Selenium was updated with the release of Selenium 4. This release introduced several new features, including relative locators, which allows testers to describe where an element is on a page using human language. In addition, Selenium 4 added support for handling authentication, intercepting and stubbing out network traffic, and capturing JavaScript errors. Furthermore, this release brought testers new support for Chromium-based Edge out of the box.  

Along with this trend, PractiTest’s 2021 State of Testing report from April of this year, showed that 90% of organizations were actively implementing testing automation into their processes throughout 2021. In addition, 96% of respondents reported that they believe test automation patterns, principals, and practices are now critical for businesses. The report also showed that 97% of those surveyed believed that functional testing automation has become important for a company’s success. 

The report also showed that there is a divide among testing teams as 59% shifted left in 2021 while 40% shifted right with practices such as testing in production or chaos engineering. However, when the report was published in April, the number of teams shifting right was on a downward trend. 

Following the shift software teams are seeing towards automated testing, earlier this year SmartBear, a provider of software development and quality tools, expanded its support of codeless, automated testing for mobile and ERP applications. The company integrated its UI test automation tool, TestComplete, with its native mobile device cloud, BitBar. 

This integration allows TestComplete users to create a codeless mobile test and then use that test in BitBar across devices. With this, the company also increased its support for testing enterprise applications such as Salesforce, Oracle EBS, and SAP.

Read our other Year in Review stories here.