Expedited HIV Testing

Background

According to the U.S. Centers for Disease Control and Prevention (CDC), about 1.15 million people are living with HIV in the United States, and it has been estimated that about 18% of these individuals are unaware of their HIV serostatus. Additionally, it is estimated that 50,000 new HIV infections occur in the United States each year. It is important to identify persons who are infected with HIV as soon as possible after infection, in order both to link them to health care services and to reduce the risk that they will unknowingly transmit HIV to others.

In order to identify those with HIV infection, the CDC recommends routine voluntary HIV screening for all adults, adolescents, and pregnant women. Nevertheless, many people are reluctant to be tested, and many clinics do not offer routine testing. With expedited HIV testing, clients can be tested and receive their preliminary results during a single visit. The goals of expedited testing are to identify HIV infection as early as possible after initial infection and to do so in as little time as possible (negative results, indeterminate results, and confirmed positive test results are available during the same visit that testing is done). This makes it possible to link persons testing HIV positive to HIV medical care and other supports as quickly as possible. Expedited testing also allows for the efficient management of clients in need of urgent medical treatment (such as pregnant women) and situations requiring quick clinical decision making (such as assessment for postexposure prophylaxis).

Expedited HIV tests include both traditional nonlaboratory-performed rapid tests and antigen/antibody (Ag/Ab) laboratory-based tests. The Ag/Ab 4th-generation tests detect both HIV p24 antigen and anti-HIV antibodies (for HIV-1 and/or HIV-2). The 4th-generation tests are more sensitive during the acute phase of HIV infection than are the previous-generation screening immunoassay tests (including nonlaboratory-based rapid tests), so they are capable of diagnosing HIV infection at an earlier stage (as early as 2-3 weeks after infection). One laboratory-based 4th-generation test is capable of delivering the preliminary results within 1 hour.

Because of the greater sensitivity of 4th-generation laboratory-based immunoassays in identifying HIV at earlier stages of infection, it is now recommended that these tests be done whenever possible for HIV screening. Interestingly, 4th-generation testing is less expensive per test than the point-of-care (POC) rapid tests in the United States.

Clients and Settings for Expedited Testing

Expedited HIV testing is important in settings in which the availability of HIV test results would influence medical care immediately, or in routine screening in settings where HIV prevalence is high or clients are not likely to return for the test results. Settings in which the use of highly sensitive 4th-generation HIV Ag/Ab testing from a laboratory is preferable include labor and delivery facilities (where identification of HIV infection is critical in preventing perinatal transmission), prenatal care facilities, hospital emergency departments, urgent care and acute care clinics, sexually transmitted disease clinics, drug treatment clinics, hospitals, and other clinical care or testing sites in communities with a high prevalence of HIV. In high-risk jurisdiction settings such as jails and mobile health service vans, and in community outreach programs where access to an on-site laboratory does not exist, nonlaboratory-based rapid testing is still recommended.

Expedited HIV Tests

The U.S. Food and Drug Administration (FDA) has approved three 4th-generation HIV Ag/Ab tests for use in the United States (see Table 1). Federal regulations under the Clinical Laboratory Improvement Amendments (CLIA) program categorize tests as waived, moderate complexity, or high complexity. Many rapid tests are approved as CLIA-waived tests (see Table 2), meaning that they may be performed at the POC after appropriate staff training and with procedures in place to ensure quality control. These tests use whole blood or oral fluid and require a few simple steps to perform. Other rapid tests are "nonwaived" tests and must be performed in laboratories. Results for rapid tests performed at the POC are available in less than 30 minutes; results for expedited tests done in a laboratory should be available within 1 hour.

As mentioned above, 4th-generation laboratory-based tests are recommended for HIV screening. In cases wherein laboratory-based 4th-generation HIV testing is not available, then 2nd- or 3rd-generation antibody POC rapid testing may be done with the knowledge that a person in seroconversion may test falsely negative.

Table 1. FDA-Approved 4th-Generation HIV Tests for Laboratory Use Only (CLIA Moderate- or High-Complexity Tests
Test Name Time to
Test Result
Target Analyte
(Test Generation)
Sensitivity for Established HIV-1 Infection & Sensitivity for HIV-2 Infection (%)
(95% Confidence Interval)
Specificity for Established HIV-1 Infection (%)
(95% Confidence Interval)
Approved Specimen Types & Volume Assay Format

Adapted from U.S. Food and Drug Administration. Complete List of Donor Screening Assays for Infectious Agents and HIV Diagnostic Assays. September 17, 2013.

Abbott Architect HIV Ag/Ab Combo Assay (fully automated CLIA moderate-complexity assay)

(Expedited)

<30 min HIV-1 p24 antigen and antibodies to HIV-1/2
(4th generation)
Plasma/Serum
HIV-1 p24: 100
(94.3-100)
HIV-1: 100
(99.63-100)
HIV-2: 100
(98.2-100)
Plasma/Serum
99.8
(99.6-99.9)
Plasma/Serum
150 µL
Chemiluminescent microparticle immunoassay
Bio-Rad GS HIV Combo Ag/Ab EIA (manual or semi-
automated CLIA high-complexity assay)
>3 hours HIV-1 p24 antigen and antibodies to HIV-1/2
(4th generation)
Plasma/Serum
HIV-1: 100
(99.7-100);
HIV-2: 100
(98.1-100)
Plasma/Serum
99.87
(99.76-99.93)
Plasma/Serum
75 µL
Enzyme immunoassay micro-well format
Alere Determine HIV-1/2 Ag/Ab Combo 20 minutes HIV p24 antigen and antibodies to HIV-1 and/or HIV-2
(4th generation)
Whole Blood
99.9
(99.4-100)
Whole Blood
99.6
(99.2-99.8)
Plasma/Serum

Whole Blood

Immunoassay
MultiSpot
HIV-1/2
Rapid Test
15 minutes Antibodies to HIV-1 and HIV-2 (detection and differentiation)
(3rd generation)
100%
(99.9-100)
99.9%
(99.8-100)
Plasma/Serum Immunoassay
Table 2. FDA-Approved HIV Rapid Screening Assays for Point-of-Care Testing
Test Name Time to Test Result Target Analyte (Test Generation) Sensitivity for Established HIV-1 Infection & Sensitivity for HIV-2 Infection (%)
(95% Confidence Interval)
Specificity for Established HIV-1 Infection (%)
(95% Confidence Interval)
Approved Specimen Types Assay Format

Adapted from U.S. Food and Drug Administration. Complete List of Donor Screening Assays for Infectious Agents and HIV Diagnostic Assays. September 17, 2013.

SURE CHECK HIV-1/2 ASSAY

(Clearview Complete HIV 1/2)

<15 minutes Antibodies to HIV-1 and/or HIV-2; point-of-care test 99.7
(98.9-100)
99.9
(99.6-100)
Fingerstick & Whole Blood (Venipuncture, Fingerstick) Rapid Immunoassay
Clearview

HIV-1/2
STAT-PAK ASSAY

15 minutes Antibodies to HIV-1 and/or HIV-2; point-of-care test 99.7
(98.9-100)
99.9
(99.6-100)
Fingerstick & Whole Blood (Venipuncture, Fingerstick) Rapid Immunoassay
OraQuick ADVANCE Rapid HIV-1/2 Antibody Test 20 minutes Antibodies to HIV-1 and/or HIV-2; point-of-care test 99.3
(98.4-99.7)
Oral Fluid
99.8
(99.6-99.9)
Oral Fluid
Oral Fluid, Whole Blood (Venipuncture, Fingerstick) Rapid Immunoassay
99.6
(98.5-99.9)
Whole Blood
100
(99.7-100)
Whole Blood
Chembio DPP HIV-1/2 Assay <40 minutes Antibodies to HIV-1 and/or HIV-2; point-of-care test 98.9
(98-99.4)
Oral Fluid
99.9
(99.7-99.9)
Oral Fluid
Oral Fluid, Whole Blood (Venipuncture, Fingerstick) Rapid Immunochromatographic Assay
99.8
(99.2-99.9)
Fingerstick Whole Blood
100
(99.8-100)
Fingerstick Whole Blood
Uni-Gold Recombigen HIV-1/2 10 minutes Antibodies to HIV-1 and/or HIV-2; point-of-care test 100
(99.5-100)
99.7
(99.0-100)
Whole Blood (Venipuncture, Fingerstick) Rapid EIA
bioLytical INSTI
HIV-1 Ab Test
60 seconds Antibodies to HIV-1; point-of-care test 99.8
(99.3-99.9)
100
(99.7-100)
Whole Blood (Fingerstick) Rapid Flow-Through Immunoassay

Interpreting Test Results

All FDA-approved tests are highly sensitive and specific. As previously mentioned, 4th- generation HIV Ag/Ab tests have significantly greater sensitivity to very recent (acute) HIV infection. The negative predictive value of all rapid and expedited HIV tests is close to 100%. That means a client who receives a negative rapid test result almost assuredly is not infected, barring recent exposures (e.g., sexual contact or needle sharing with an infected person within the past 1-3 months, depending on the test used).

For clients who test reactive (positive) on a rapid or expedited test, the result is considered preliminary and must be confirmed. Traditionally, confirmation has been done by use of either a Western blot (WB) or immunofluorescence assay (IFA). However, neither of these confirmatory tests is expedited, and neither is able to differentiate HIV-1 and HIV-2 infections simultaneously. The confirmatory test currently recommended by the CDC is one that is able to differentiate HIV-1 and HIV-2 antibodies and is expedited (e.g., MultiSpot HIV-1/HIV-2 Rapid Test). If the confirmatory test result is positive, the client is considered to be infected with HIV. If the confirmatory test result is negative (no HIV Ab bands with a WB test or no visible reaction on the MultiSpot in the HIV-1 and/or HIV-2 Ab areas) or indeterminate (with the WB test, greater than 0 bands but too few bands to be considered positive), then an HIV RNA-1 test should be done immediately to check for early infection (Figure 1). In this case, a detectable HIV RNA (unless very low) will indicate early HIV infection - the client is most likely HIV infected and is seroconverting from antibody negative to positive status. The HIV-1 RNA test should be done regardless of the original HIV screening test (4th-generation Ag/Ab or earlier-generation Ab). With detectable HIV RNA, the client should be considered infected, but an HIV confirmatory (WB or IFA) antibody test should be repeated in roughly 2-4 weeks to determine HIV antibody status. In the case of possible HIV-2 infection, consultation with an HIV specialist is recommended.

The positive predictive value of a single positive rapid or expedited HIV test result depends on the specificity of the test and the HIV prevalence in the community. The high specificity of the rapid or expedited tests means that, if a test result is positive, the likelihood that a client is truly HIV infected depends on the local HIV prevalence. In a population with a high HIV prevalence, a positive test result is likely a true positive, but in a population with a low HIV prevalence, that result has a greater chance of being a false positive.

Figure 3: 4th-Generation HIV Testing Algorithm

4th-Generation HIV Testing Algorithm

Centers for Disease Control and Prevention. Detection of acute HIV infection in two evaluations of a new HIV diagnostic testing algorithm - United States, 2011-2013. MMWR Morb Mortal Wkly Rep. 2013 Jun 21;62(24):489-94.

Information for the Client

Educating the Client Before Testing

It is important to offer expedited HIV testing as part of a broader health screening, to educate clients about HIV infection and about the test, and to give them an opportunity to ask questions and to decline testing. The provider should emphasize that a second test is always performed in order to confirm a positive preliminary screening (laboratory or POC) test result. When possible, expedited or rapid testing should be made available during a regular visit so that clients do not face additional waiting time, and so that HIV infection can be detected as early as possible.

Giving Reactive (Preliminary Positive) Rapid Test Results

Example of simple language to use outside labor and delivery settings

The following wording is suggested when the client's rapid (nonconfirmed) test result is positive (or the expedited confirmatory testing is negative [and therefore the final result is "indeterminate"]):

"Your preliminary screening test result was positive, but we won't know for sure if you are infected with HIV until we get the results from your confirmatory test. In the meantime, you should take precautions to avoid transmitting the virus. This means protecting all sex partners from possible exposure (using condoms, for example), not sharing needles or syringes for any purpose, and not sharing razors."

Emphasize the importance of a confirmatory test, arrange for the confirmatory test to be done immediately. If an expedited, confirmatory test is available (MultiSpot Rapid), the client should not leave until that test has been completed and the result given. If an expedited confirmatory test is not available, then schedule a return visit for the client to receive the test result. It is important to develop a plan for follow-up with this client during this waiting period (by phone or in-person) and to reinforce the importance of following up. (Be sure to have the client's contact information in case he or she does not return for confirmatory results.)

Example of language to use in labor and delivery settings

The following wording is suggested when the client's nonconfirmed expedited or rapid test result is positive:

"Your preliminary HIV screening result was positive. You may have HIV infection. We need to do confirmatory tests to verify this first result, but it is important to start medication immediately to reduce the risk of passing HIV to your baby while we wait for the result. It is important to delay breast-feeding until we have the confirmatory test results."

Follow-Up for Results of Confirmatory Tests

Clinical sites that offer expedited or rapid HIV testing should have a protocol for conveying the results of preliminary and confirmatory positive HIV test results to clients. With rapid tests and expedited laboratory-based testing, the client may be given the confirmatory results on the same day tested. If expedited laboratory-based confirmatory testing (MultiSpot Rapid), is not available, blood for confirmatory WB or IFA must be collected. In this case, results generally will not be available the same day, but appropriate specimen collection and test ordering should be done before the client leaves on the day the preliminary positive result is given.

If the confirmatory result is negative or indeterminate (after a positive preliminary result), testing for HIV-1 RNA must be done.

Sites should either provide confirmatory notification services in-house or have mechanisms in place for notifying clients of their test results. All clients with confirmed positive HIV test results should be referred immediately for HIV care, community-based HIV services, or health department disease intervention specialists (who are trained to link people to care). Testing sites should establish reliable referral pathways to qualified HIV care providers with follow-up policies and procedures in place to make sure that linkage to care actually occurred.

Client Education

In general settings and in situations not involving labor and delivery, advise clients of the following:

  • Expedited laboratory and rapid nonlaboratory HIV testing is an important component of health screening. Learning early that they have HIV infection can help clients better maintain their health.
  • Knowing that they have HIV infection can help clients start treatment as soon as possible, and to take precautions to prevent transmission of HIV to others.
  • Clients can refuse an HIV test, and it will not affect the care they receive.
  • The results from expedited or rapid tests are available at the same visit, usually in less than 1 hour.
  • The expedited 4th-generation Ag/Ab tests are very accurate and are better at identifying newly infected persons than the 2nd- and 3rd-generation rapid and laboratory screening tests.
  • If the expedited or rapid test result is positive, a second, confirmatory test always is done in order to provide assurance that the screening test result was accurate; and, if the confirmatory test is either negative or indeterminate, a third test (HIV viral load) needs to be done to determine whether the client is infected.
  • It is important that clients return for the results of all confirmatory tests.
  • If a client's expedited or rapid test result is negative, that client is most likely not infected with HIV, unless the infection occurred within the past month--the test may not detect very recent infection.
  • Test results are kept confidential. However, if a confirmatory test result is positive, most state laws require that information to be reported to the health department.
  • There are clinics and other resources to help clients obtain more information as well as counseling, care, or treatment. The provider should provide specific referrals to these as well as assist the client in linkage to the referral site as soon as possible.

References

  • Association of Public Health Laboratories. Suggested reporting language for the HIV laboratory diagnostic testing algorithm. November 2013.
  • Beckwith CG, Atunah-Jay A, Cohen J, et al. Feasibility and acceptability of rapid HIV testing in jail. AIDS Patient Care and STDS. 2007 Jan;21(1):41-7.
  • Branson B. The future of HIV testing. J Acquir Immune Defic Syndr. 2010 Dec 15:55(Suppl 2):S102-05.
  • Centers for Disease Control and Prevention. Estimated HIV incidence in the United States, 2007-2010. HIV Surveillance Supplemental Report 2012;17 (No. 4). Published December 2012.
  • Centers for Disease Control and Prevention. Detection of acute HIV infection in two evaluations of a new HIV diagnostic testing algorithm - United States, 2011-2013. MMWR Morb Mortal Wkly Rep. 2013 Jun 21;62(24):489-94.
  • Centers for Disease Control and Prevention. Draft Recommendations: Diagnostic Laboratory Testing for HIV Infection in the United States. Presented at the 2012 HIV Diagnostics Conference Feedback Session held on December 14, 2012. Accessed December 1, 2013.
  • Colfax GN, Buchbinder SP, Cornelisse PG, et al. Sexual risk behaviors and implications for secondary HIV transmission during and after HIV seroconversion. AIDS. 2002 Jul 26;16(11):1529-35.
  • Hutchinson AB, Corbie-Smith G, Thomas SR, et al. Understanding the patient's perspective on rapid and routine HIV testing in an inner-city urgent care center. AIDS Educ Prev. 2004 Apr;16(2):101-14.
  • Marks G, Crepaz N, Senterfitt JW, et al. Meta-analysis of high-risk sexual behavior in persons aware and unaware they are infected with HIV in the United States: implications for HIV prevention programs. J Acquir Immune Defic Syndr. 2005 Aug 1;39(4):446-53.
  • Masciotra S, McDougal JS, Feldman J, et al. Evaluation of an alternative HIV diagnostic algorithm using specimens from seroconversion panels and persons with established HIV infections. J Clin Virol. 2011 Dec;52 Suppl 1:S17-22.
  • Nasrullah M, Wesolowski LG, Meyer WA 3rd, et al. Performance of a fourth-generation HIV screening assay and an alternative HIV diagnostic testing algorithm. AIDS. 2013 Mar 13;27(5):731-7.
  • U.S. Food and Drug Administration. Complete List of Donor Screening Assays for Infectious Agents and HIV Diagnostic Assays. Accessed December 1, 2013.
  • U.S. Preventative Services Task Force. Screening for HIV. April 2013. Accessed December 20, 2013.

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Abbreviations for Dosing Terminology

BID
twice daily
BIW
twice weekly
IM
intramuscular (injection), intramuscularly
IV
intravenous (injection), intravenously
PO
oral, orally
Q2H, Q4H, etc.
every 2 hours, every 4 hours, etc.
QAM
every morning
QD
once daily
QH
every hour
QHS
every night at bedtime
QID
four times daily
QOD
every other day
QPM
every evening
TID
three times daily
TIW
three times weekly