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4A0-N01 Nuage Networks VCS Fundamentals

Nuage Networks Virtualized Services Platform (VSP) Fundamentals course presents the technology, techniques, and best practices for implementing a software defined networking (SDN) solution for datacenters. The course begins with an explanation of the traditional datacenter network architecture, its limitations, and the drivers and evolution of network virtualization. The Nuage Networks software and hardware-based products and SDN solutions are covered in detail. Emphasis is placed on common SDN use cases and implementation of common SDN services/applications on the Nuage Networks Virtualized Services Platform. Cloud orchestration and integration of cloud management systems are also introduced. Students will conduct practical hands-on lab exercises throughout the course to ensure implementation-level knowledge of Nuage Networks products and SDN service solutions.

Nuage Networks Virtualized Services Platform Fundamentals.
Exam number 4A0-N01

COURSE OBJECTIVES After completing the course, students should be able to: ■■ Describe the traditional datacenter architecture and its limitations
■■ Describe the evolution of network virtualization
■■ Describe the Nuage Networks SDN solutions
■■ Explain common Nuage Networks SDN use cases
■■ Deploy common SDN services and applications on Nuage Networks VSP
■■ Explain the concept of cloud orchestration and how different cloud management systems are integrated with Nuage Networks
■■ Explain the concept of virtualization in the datacenter and the role of SDN and Network Functions Virtualization (NFV)
■■ Describe the basics of hypervisors and common hypervisor technologies
■■ Explain the Nuage Networks virtualization solution and its value proposition
■■ Describe the Nuage Networks VSP and its software suite
■■ Explain cloud service network instantiation with Nuage Networks
■■ Explain the purpose of the Virtualized Services Directory (VSD)
■■ Explain the function and key components of the Nuage Networks SDN controller — the Virtualized Services Controller (VSC)
Describe the Nuage Networks Virtual Routing & Switching (VRS) agent and the virtual line card concept
■■ Explain the function and network position of the Nuage
Networks Virtualized Services Gateway (VSG)
■■ Describe the hardware-based 7850 VSG/VSA and the software-based Virtualized Routing and Switching Gateway (VRS-G)
■■ Describe the function and network position of the Nokia 7750 SR Datacenter Gateway and its integration into the Nuage Networks architecture
■■ Explain the security and forwarding policies provided by the Nuage Networks VSP and how to deploy them
■■ Describe service chaining and how to deploy service chaining in the Nuage Networks VSP
■■ Describe the Layer 2 and Layer 3 datacenter interconnect solutions and how to deploy them
■■ Describe the QoS and statistics policy options on the Nuage Networks VSP
■■ Explain how QoS policies are configured and enforced
■■ Describe shared network concepts such as floating IPs, public zone and how to implement them
■■ Explain the Layer 2 (L2) connectivity model in Nuage Networks VSP and how to instantiate L2 connectivity between VMs
■■ Describe Nuage Networks VSG/VRS-G function and how to instantiate connectivity between VMs and physical servers
■■ Describe the virtual machine (VM) migration workflow and implement VM migration using Nuage Networks VSP
■■ Explain what a cloud management system is and the two models for cloud management system (CMS) integration with the VSD and VRS
■■ Describe the various management architectures (Openstack, vCenter, vCloud, CloudStack) and their integration with Nuage Networks
■■ Describe the Nokia NFV solution and the CloudBand™ solution, and their benefits

Module 1 – Datacenter Network Architecture
■■ Virtualization in the datacenter
■■ Virtualized network in the datacenter
■■ Nuage Networks datacenter
Module 2 – Product Introduction
■■ Nuage Networks product portfolio introduction
■■ Nuage Networks Virtualized Services Directory (VSD)
■■ Nuage Networks Virtualized Services Controller (VSC) and Virtual Routing and Switching (VRS)
■■ Nuage Networks Gateway (7850 Virtualized Services Gateway and Virtualized Routing and Switching Gateway)
■■ Nokia 7750 Datacenter Gateway
Module 3 – Use Cases
■■ Security and forwarding policy
■■ Service chaining
■■ Datacenter interconnection
■■ QoS and statistics policy
■■ Shared network
■■ Layer 2 domain
■■ Baremetal integration
■■ Virtual machine (VM) migration
Module 4 – Cloud Orchestration
■■ Cloud orchestration overview
■■ CMS integration
■■ Network Functions Virtualization (NFV) and
■ Nokia CloudBand
Nuage Networks VCS Fundamentals
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Nuage Networks VCS Fundamentals
Question: 36
Which of the following is NOT an improvement provided by the backhaul VPLS?
A. Reducing the number of EVPN on the HV.
B. Reducing the number of VXLAN tunnels.
C. Reducing the size of MAC address table.
D. Reducing the consumption of bandwidth.
Answer: B
Question: 37
Which of the following is NOT a goal of NFV?
A. Reduce equipment cost
B. Faster time-to-market for new services
C. Efficiency through automation
D. Increase network bandwidth
Answer: B
Question: 38
The ML2 plug-in is part of which OpenStack project?
A. Neutron
B. Ironic
C. Nova
D. Heat
Answer: A
Question: 39
On which Kubernetes node is the Nuage-kube-mon component installed?
A. On the worker node.
B. On the master node.
C. On the network node.
D. On a dedicated gateway node.
Answer: A
Question: 40
What statement about policy groups is FALSE?
A. Several vPorts ( in the same or different subnets) can be associated with one policy
B. One vPort can be associated with multiple policy groups.
C. For an ingress security policy, if a hardware endpoint policy group is chosen as the
source, the destination must also be hardware endpoints.
D. D. The policy group is the syntactic equivalent of the security group used by cloud
management systems.
Answer: A
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Wed, 13 Jul 2022 09:51:00 -0500 en text/html https://ung.edu/learning-support/placement-test-practice.php
Keysight (KEYS) Partners With Nokia to Test 6G Compatibility

Keysight Technologies, Inc. KEYS recently collaborated with Nokia Bell Labs to test the propagation characteristics of sub-terahertz (sub-THz) spectrum that is essential for 6G network. The analysis is likely to sow the seeds of innovative software and hardware offerings for the seamless transition to superfast data speed, ultra-low latency and near-infinite bandwidth of 6G network.

Nokia Bell Labs operates as the industrial research lab of Nokia Corporation NOK and aims to develop sustainable technologies that will likely have a demonstrable impact on society. As the world stands at the cusp of the 6G revolution, it has partnered with Keysight to test active sub-THz components, such as amplifiers, mixers and frequency converters, to ensure that they do not introduce additional signal distortion into communications systems.

Although sub-THz spectrum offers an ideal platform for transmitting 6G signal, it has not been traditionally used for cellular communications due to its propagation characteristics, which hamper signal quality and affect performance. Leveraging Keysight PNA-X Vector Component Analyzer solution and a Nokia power amplifier (PA) developed for use in 6G D-band wireless communications systems, the analysis measured the signal distortion introduced in the communications system by the component. This is likely to enable Nokia Bell Labs to better understand the PA’s performance to optimize its 6G transmission system design in the near future.

Keysight is witnessing solid adoption of its electronic design and test solutions. Strong demand for its solutions has been a key catalyst behind robust top-line growth.

Electronic devices form the very fulcrum of Internet of Things (IoT) services, wireless devices, data centers and 5G technologies. The rapid adoption of these devices is increasing the demand for electronic testing equipment. Further, technological advancements in mobile communications, semiconductors and automotive markets are likely to drive growth. Moreover, the rising demand for power management applications is a key catalyst for Keysight. Sturdy efforts toward modifying the Internet infrastructure and the evolution of smart cars & autonomous-driving vehicles bode well for its growth.

Keysight’s efforts in emerging growth markets like IoT and high-speed data centers bode well for the top line. Particularly, management’s focus on Automotive and Energy, and Aerospace and Defense domains augurs well in the long haul. The company is expected to benefit from the growing proliferation of electronic content in vehicles, momentum in space and satellite applications and rising adoption of driver-assistance systems globally.

It has gained 13% over the past year compared with the industry’s rise of 14.1%.

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Keysight currently carries a Zacks Rank #3 (Hold).

You can see the complete list of today’s Zacks #1 Rank (Strong Buy) stocks here.

InterDigital, Inc. IDCC, sporting a Zacks Rank #1, delivered an earnings surprise of 170.89%, on average, in the trailing four quarters. In the last reported quarter, it pulled off an earnings surprise of 579.03%. It has a long-term earnings growth expectation of 13.9%.

It is a pioneer in advanced mobile technologies that enables wireless communications and capabilities. The company engages in designing and developing a wide range of advanced technology solutions, which are used in digital cellular and wireless 3G, 4G and IEEE 802-related products and networks.

Viasat Inc. VSAT, sporting a Zacks Rank #1, enjoys a leading position in the satellite and wireless communications market. Headquartered in Carlsbad, CA, it designs, develops and markets advanced digital satellite telecommunications and other wireless networking and signal processing equipment. The company serves its high-bandwidth, high-performance communications solutions to public as well as military, enterprises and government enterprises.

Viasat is ramping up investments in the development of its revolutionary ViaSat-3 broadband communications platform, which will have nearly 10 times the bandwidth capacity of ViaSat-2. These satellites will be capable of covering one-third of the world, including all Americas.

To read this article on Zacks.com click here.

Wed, 31 May 2023 00:26:00 -0500 en-US text/html https://www.msn.com/en-us/money/other/keysight-keys-partners-with-nokia-to-test-6g-compatibility/ar-AA1bWhRF Reading Comprehension Practice Test

Reinforce memorizing comprehension skills with this simple practice quiz! Each of the illustrated paragraphs in this worksheet is followed by a multiple-choice question designed to help learners' reinforce their memorizing comprehension skills. Designed for second graders, this appealing, playful worksheet is a fun way to practice, review, or even test concepts including sequence of events, identifying the central message, and drawing conclusions.

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Sun, 10 Mar 2013 14:49:00 -0500 en text/html https://www.education.com/worksheet/article/practice-test-reading-comprehension/
How to Use practice tests to Study for the LSAT No result found, try new keyword!Likewise, it’s a bad idea to take the LSAT without first training with real practice tests. That said, very few athletes run daily marathons. Instead, they vary their training with shorter ... Fri, 28 Oct 2022 12:55:00 -0500 text/html https://www.usnews.com/education/blogs/law-admissions-lowdown/articles/how-to-use-practice-tests-to-study-for-the-lsat Practice Tests for IGCSE English as a Second Language

The tests will help familiarise students with the format and requirements of the IGCSE E2L memorizing and Writing/Listening and Speaking papers. Teachers will find them a valuable source of stimulating practice material which will engage the interest of students at this level, particularly those preparing for academic study. The material is also recommended for use with non-exam students at intermediate to upper-intermediate level. The resources include: stimulating authentic texts on a wide range of subjects, reflecting the educational nature and international perspective of the IGCSE; realistic tasks, relevant to students’ interests and experience; detailed information about the examination, and teacher’s guidelines on timing and marking; invaluable practical advice to the student; model summaries and compositions/full audio scripts and examiner’s notes in the With Key editions. Endorsed by CIE.

Mon, 25 Feb 2013 09:21:00 -0600 en text/html https://www.cambridge.org/us/education/subject/english/english-second-language/practice-tests-igcse-english-second-language
Nokia unveils 4G, 5G core network software solutions

Nokia unveiled its new network software solutions for the field and wide area network (FAN/WAN) needs of public safety and power utilities.

The vendor said in a release that this launch expands its portfolio range for mission-critical enterprises and governments.

Nokia said its core enterprise solutions are optimized to help enterprises take advantage of secure carrier grade capabilities and digitalize their network infrastructure to realize increased automation, productivity and efficiency.

The Finnish vendor estimated that the addressable market for core networks solutions in the enterprise FAN/WAN private wireless communications space is expected to increase 50% and reach EUR1.5 billion ($1.6 billion) by 2027 from approximately EUR1 billion today.

Nokia also highlighted that its core enterprise solutions are designed for enterprises and governments that have networking requirements similar to a communication service provider. These new solutions are tailored to the specific mission-critical network needs of public safety and power utilities and include highly optimized footprint and operational requirements and streamlined deployment and support, according to the vendor.

The solutions, which will be commercially available later this year, provide unified 4G and 5G data, voice and subscriber/device management capabilities. They also feature broadband-enhanced communication tools for public safety and offer the introduction of IoT in power utilities, according to the company.

Fran Heeran, SVP and general manager of core networks, cloud and network services at Nokia, said: “This exciting new evolution of our Core portfolio further enhances Nokia’s leading position in private wireless. Nokia core enterprise solutions will provide important catalysts for accelerating digital transformation for enterprises in public safety and power utilities. They will modernize large scale enterprise networks, as well as provide important broadband capabilities and a clear and path to deploying private 5G for the WAN.”

“A select set of government and business operations provides essential safety, energy, and transportation functionality required for a safe society and robust economic growth. These organizations have a unique requirement for wide-area wireless operations across sweeping geography with secure, ubiquitous, and high-quality connectivity enabled by private 4G and 5G networks. Nokia’s pre-integrated, sector-optimized mission-critical core network solutions can reduce risk and help speed challenging wide-area private network deployments,” said Ken Rehbehn, principal analyst at CritComm Insights.

Earlier this year, Nokia and Kyndryl extended a previous partnership to further accelerate adoption of cellular-backed Industry 4.0 solutions and announced they are working with security specialist Palo Alto Networks to open a partner innovation lab in the U.S.

The two companies said they now tally 100 active engagements around private 5G and 4G networks, as well as mobile edge computing (MEC) technologies, for enterprises.

According to the companies, 90% of those engagements—which span “from advisory or testing, to piloting, to full implementation”—are with manufacturing firms.

Wed, 31 May 2023 04:02:00 -0500 en-US text/html https://www.rcrwireless.com/20230531/private-networks/nokia-unveils-4g-5g-core-network-software-solutions
Rules of the Road practice questions #2

Review the rules of the road with this traffic signs and signals practice test. Your teen will answer questions about signs and traffic signals in this practice driving test. Maybe your child knows what a stop sign means, but does he know what an inverted red triangle represents? Help him get ready for the written learner's permit test with this traffic signs and signals driving practice test.

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Tue, 24 May 2011 23:00:00 -0500 en text/html https://www.education.com/worksheet/article/practice-driving-test-2/
Fundamentals of cyber security - AQA test questions - AQA No result found, try new keyword!Which piece of software is not malware? A form of software testing used to simulate an external hacking attempt A form of software testing used to simulate an internal hacking attempt A form of ... Thu, 16 Mar 2023 07:02:00 -0500 en-GB text/html https://www.bbc.co.uk/bitesize/guides/znnny4j/test OHS will work fundamentals in spring practice

Apr. 22—Owensboro High School started spring football practice with three days at the beginning of this week. Fundamentals will be big with younger players moving up to fill several spots OHS will have open next season.

There are around 40 out for spring football, with many OHS football players going in spring sports like track and baseball.

"We take the 40 we've got, and it's almost strictly fundamentals," OHS coach Jay Fallin said. "Football is a fundamental sport. We can spend three weeks where the linemen work on footwork, hand placement; the receivers are working on catching the ball, running great routes; defense can work on angles and alignment."

Owensboro is coming off a hugely successful run over the last four seasons, and it said goodbye to a talented and deep senior class that was part of four straight years reaching the Class 5-A state semifinals.

OHS was 23-5 in the last two seasons alone.

Finding players to fill those voids will be important, and some of that process starts in the spring.

"Every year somebody surprises you in the spring," Fallin said.

A player might not have been considered for a rotation spot after the previous season, but could work hard in the weight room, transform himself and by the next spring and is ready.

"I think high school football is one of the last remaining sports, where if you work hard for four years, by the time you're a senior, you're almost assured we can find a spot for you," Fallin said. "As coaches, we're trying to develop everybody to have a role."

All of the combinations of special teams can have huge impacts on games, and those are spots that need to be filled.

"It's a different experience every year," Fallin said of spring practice. "You can talk about encouraging kids to play multiple sports, or you can be about it. This year we've got almost 30 kids running track and playing baseball."

That leaves plenty of room for players in spring practice to move up or get noticed.

It can be a progression that began in late October and November of the previous season if a team made a deep run in the KHSAA football playoffs.

"When you have the kind of success we've had, the last four years played in the semifinals, that's 16 extra weeks of practice over those years," Fallin said. "Really intense practices, too, and that makes a huge difference for us."

After freshman football is over, those players can go to varsity practice during the playoffs and observe while not getting reps.

"They're with us, seeing how we practice," Fallin said, "It propels them into their sophomore year. They're a lot wiser. The importance of those practices can't be overstated."

This time frame in the spring is good for catching some good weather, and early enough to avoid end of year activities like prom.

"This is what we've done the last several years," Fallin said. "The week after spring break we hand out equipment, last Monday we hit ground running."

Teams can practice 10 times over the course of three weeks. After spring football, OHS will be back lifting, doing workouts early mornings in June until the KHSAA Dead Period in late June-early July.

Fri, 21 Apr 2023 21:21:00 -0500 en-US text/html https://sports.yahoo.com/ohs-fundamentals-spring-practice-091600490.html
How accurate are rapid, point-of-care tests for HIV?

Key points

  • Rapid tests are usually reliable for long-standing infections, but are sometimes unable to detect accurate HIV infections acquired in the past few weeks.
  • Many tests are based on older ‘second-generation’ technology, but a ‘fourth-generation’ test with better performance is available.
  • Like any screening test, a reactive (‘positive’) result must be confirmed with one or two follow-up tests.

Rapid tests are often referred to as point-of-care tests because rather than sending a blood demo to a laboratory, the test can be conducted and the result read in a doctor’s office or a community setting, without specialised laboratory equipment.

Most point-of-care tests require a tiny demo of blood (the fingertip is pricked with a lancet). Other tests require oral fluid (an absorbent pad is swabbed around the outer gums, adjacent to the teeth). They are called ‘rapid’ tests because the result can usually be given within a few minutes.

Most rapid tests detect HIV antibodies. They are not part of HIV itself, but are produced by the human body in response to HIV infection. In the weeks after exposure to HIV, the immune system recognises some components of the virus and begins to generate HIV antibodies in order to damage, neutralise or kill it (this period is known as ‘seroconversion’). These antibodies persist for life.

In contrast, the recommended laboratory tests also detect p24 antigen, a protein contained in HIV's viral core that can be detected sooner than antibodies. Most rapid tests, with the exception of the  Determine HIV Early Detect and Determine HIV-1/2 cannot detect p24 antigen.

The accuracy of point-of-care tests is not always equal to those of laboratory tests, especially in relation to accurate infection. This is for two main reasons:

  • What the test looks for. While one antibody/antigen test is available, the other tests look for antibodies only. Moreover, some can only detect immunoglobulin G (IgG) antibodies, but not immunoglobulin M (IgM) antibodies, which appear sooner.
  • The demo taken. Point-of-care tests are usually performed on whole blood taken from a fingerprick. This has a lower concentration of antibodies and p24 than plasma. Samples of oral fluid have a concentration of antibodies that is lower still. (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.)

As a result, the window period of commonly used rapid tests such as the  Determine HIV Early Detect and the INSTI HIV-1/HIV-2 Antibody Test may be one to two weeks longer than for fourth-generation laboratory tests. Other rapid tests, based on older technology, may have longer window periods than this.

Rapid tests can be performed by staff with limited laboratory training. However, memorizing the test result relies on subjective interpretation, and when the result is borderline, experienced staff deliver more consistently accurate results. In a setting with low prevalence of HIV, staff may not see enough true positive samples to gain experience in interpreting test results.

It is good practice for test results to be re-read by a second member of staff, within the time frame specified on the test packaging. Organisations using point-of-care tests must maintain strong links with a pathology laboratory that provides support with clinical governance and quality assurance.

When used in a population with a low prevalence of HIV, false positive results can be a problem. The tests always produce a small number of false positive results, but in a setting where very few people have HIV, the majority of apparent positive results will in fact be incorrect. However, as the proportion of people with HIV being tested increases, the true positives start to outnumber false positives. This means it is more appropriate to use point-of-care tests in high-prevalence populations, such as with gay and bisexual men, than in the general population.

All HIV tests need to have reactive results (a preliminary positive result) confirmed with further tests. Most providers tell people who are testing that a negative result is definitive, but that a reactive result simply indicates the need for further laboratory testing.

The accuracy of different rapid tests

A wide range of point-of-care tests have been manufactured in many countries, but only a few of them have been subject to rigorous, independent evaluations, and even fewer are marketed in the UK. Research on HIV tests is only occasionally published in medical journals. Informally, laboratory professionals may have insights into which tests perform best.

It is important to verify that any test used is CE marked. This should mean that the test conforms to European health and safety legislation, although it does not necessarily mean that test performance has been independently evaluated.

There are variations in accuracy from one test to another, with some older tests that are not usually marketed in the UK having a sub-optimal sensitivity and specificity. However, evaluations by the World Health Organization of several rapid diagnostic tests that either have CE marks or are approved by the US Food and Drug Administration (FDA), indicate that most are extremely accurate. The key measures of accuracy are sensitivity (the percentage of results that are correctly positive when HIV is actually present) and specificity (the percentage of results that are correctly negative when HIV is not present).

Of note, in the World Health Organization data below, most tests were performed with samples of plasma or serum. However, the tests are less sensitive when testing whole blood sampled from a finger prick. There is one test (the OraQuick Advance Rapid HIV-1/2) which can also test oral fluid samples in addition to blood.

Also, the figures on sensitivity are based on samples from people who had chronic (not recent) HIV infection, but the tests are less accurate in cases of accurate infection, especially those which only detect immunoglobulin G (IgG) antibodies.





OraQuick HIV-1/2 Rapid HIV-1/2 (OraSure)




HIV 1/2 STAT-PAK (Chembio)




Determine HIV Early Detect (Abbott) IgG + IgM + p24 100% 99.4%

Determine HIV-1/2 (Abbott)

IgG + IgM + p24



Uni-Gold HIV (Trinity)

IgG + IgM



INSTI HIV-1/HIV-2 Antibody Test (bioLytical)

IgG + IgM



SD BIOLINE HIV-1/2 3.0 (Standard Diagnostics)

IgG + IgM



DPP® HIV 1/2 Assay (Chembio)




There is one rapid, point-of-care test that looks for both antibodies and p24 antigen, in a similar way to antibody/antigen laboratory tests. The Determine HIV-1/2 Ag/Ab Combo was originally introduced in 2009, with an updated version that is now called the Determine HIV Early Detect launched in Europe in 2015 (the older version is still marketed in the United States and in some parts of the world).

The promise of having a ‘fourth-generation’ point of care test that detects p24 antigen is that the window period should be shortened. However, several studies found that although the older version of this test performed well in respect of established HIV infection, its ability to detect accurate HIV infection did not match that of laboratory antibody/antigen tests. The test was quite insensitive to p24 antigen, making it only marginally better than antibody-only tests in detecting acute (recent) infection.

"All HIV tests need to have reactive results (a preliminary positive result) confirmed with further tests."

The handful of studies published so far on the newer version suggests it has better performance in acute infection, although it still does not match that of antibody/antigen laboratory tests. The Determine HIV Early Detect’s sensitivity during acute infection has been variously estimated to be 28% (in three African countries), 54% (France), 65% (the Netherlands) and 88% (UK).

An analysis pooled the results of 18 separate studies in which a point-of-care test (including Determine, OraQuick, UniGold and INSTI) was compared with a more sensitive laboratory test. Compared with fourth-generation laboratory tests, the estimated sensitivity of the point-of-care tests was 94.5% (95% confidence interval 87.4-97.7) and specificity was 99.6% (99.4-99.7). Compared with RNA (viral load) tests, the estimated sensitivity was 93.7% (95% confidence interval 88.7-96.5) and specificity 98.1% (95% CI: 97.9-98.2).

Sensitivity was higher in nine studies conducted in African countries than in the nine studies conducted in the United States and other wealthy countries. This is likely to be due to different populations coming forward for screening. Whereas 4.7% of those testing positive in African studies had acute (recent) HIV infection, this figure rose to 13.6% in the high-income countries.



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.

point-of-care test

A test in which all stages, including memorizing 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.

window period

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.


An HIV antigen that makes up most of the HIV viral core. High levels of p24 are present in the blood during the short period between HIV infection and seroconversion, before fading away. Since p24 antigen is usually detectable a few days before HIV antibodies, a diagnostic test that can detect p24 has a slightly shorter window period than a test that only detects antibodies.


Because of the possibility that a positive result from a single HIV test is, in fact, a false positive, the result is described as 'reactive' rather than 'positive'. If the result is reactive, this indicates that the test has reacted to something in the blood and needs to be investigated with follow-up tests.

A study in five African countries found that the performance of point-of-care tests was sub-optimal. Samples from some countries were more likely to have false positive results than others, suggesting that tests need to be locally validated and that some tests may be more accurate in relation to some HIV subtypes than others. The researchers found a high number of false positive results, whereas false negative results were relatively rare. The specificities of the First Response HIV Card Test 1–2.0, INSTI HIV-1/HIV-2 Antibody Test, Determine HIV-1/2 and Genie Fast HIV 1/2 were all between 90 and 95%. The findings confirm that the diagnosis of HIV should not be based on results from a single HIV rapid diagnostic test. A combination of HIV tests, and more specifically an algorithm (sequence) of two or three different tests, is required to make an HIV-positive diagnosis. This is recommended in testing guidelines.

All HIV tests need to have reactive (preliminary positive) results confirmed with confirmatory tests. A particular challenge healthcare workers have with rapid tests is how to communicate a reactive result to the person testing (who may be present while the result is being read) and explain that supplementary tests are needed. These problems are less frequently faced with laboratory testing – a large enough blood demo was taken to allow for it to be tested several times and for uncertainties in the diagnosis to be resolved.

Window periods of rapid tests

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 reliably detect HIV infection until after the window period has passed. All tests have a window period, which varies from test to test.

Delaney and colleagues estimated window periods for a handful of rapid tests in a 2017 study. However, all these estimates were based on testing blood plasma. In practice, tests are usually done on fingerprick blood (obtained by pricking the finger with a lancet) and the window period is likely to be several days longer.

The fourth-generation Determine HIV-1/2 Ag/Ab Combo was estimated to have a median window period of 19 days (interquartile range 15 to 25 days). This indicates that half of all infections would be detected between 15 and 25 days after exposure. Ninety-nine per cent of HIV-infected individuals would be detectable within 43 days of exposure.

The third-generation INSTI HIV-1/HIV-2 test was estimated to have a median window period of 26 days (interquartile range 22 to 31 days). This indicates that half of all infections would be detected between 22 and 31 days after exposure. Ninety-nine per cent of HIV-infected individuals would be detectable within 50 days of exposure.

Several second-generation tests, such as OraQuick Advance Rapid HIV 1/2, Clearview HIV 1/2 STAT-PACK and SURE CHECK HIV 1/2 were evaluated. The median window period was 31 days (interquartile range 26 to 37 days). This indicates that half of all infections would be detected between 26 and 37 days after exposure. Ninety-nine per cent of HIV-infected individuals would be detectable within 57 days of exposure.

UK guidelines take a cautious approach, describing the window period for all rapid, point-of-care tests as 90 days.

If you are testing with a rapid, point-of-care test and you are concerned that you may have been exposed to HIV during the test’s window period, you could also be tested with a fourth-generation laboratory test. This requires a blood sample, taken through a needle from a vein in the arm, which is tested in a laboratory using a more sensitive test. The results should be available after a few days.

Situations in which rapid tests may not be accurate

Performance of rapid tests is poorer in a number of situations. Results may not be accurate.

What do the test results mean?

There are three possible test results:

1) Negative (may also be described as ‘non-reactive’). The test did not find any evidence of HIV infection. You probably don’t have HIV (so long as you aren’t testing in one of the situations described in the last section).

2) Reactive (often incorrectly described as ‘positive’ by manufacturers). The test assay has reacted to a substance in your blood. This does not necessarily mean that you are HIV positive. It means you need to take more tests to confirm the result. These extra tests are best done at a healthcare facility where they have access to the most accurate HIV testing technologies.

3) ‘Indeterminate’, ‘equivocal’ or ‘invalid’. The test result is unclear. Another test needs to be done.

Tue, 23 Dec 2014 15:44:00 -0600 en text/html https://www.aidsmap.com/about-hiv/how-accurate-are-rapid-point-care-tests-hiv

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