While much has been accomplished to eliminate the scourge of HIV/AIDS since its discovery nearly 3 decades ago, the condition is far from eliminated. According to the Joint United Nations Programme on HIV/AIDS, the number of people living with HIV worldwide continued to increase in 2008, reaching an estimated 33.4 million. The total number of people living with the virus in 2008 was more than 20% higher than the number in 2000 and roughly three times higher than the total in 1990.
Of those living with the condition, an estimated 31 million were adults and two million were children under the age of 15. There were approximately two million AIDS-related deaths.
Global organizations such as the World Health Organization have worked diligently to raise awareness of HIV, with a focus on detection. In addition, the Centers for Disease Control and Prevention (CDC) has determined that testing and treatment of sexually transmitted diseases (STDs) can be an effective tool in preventing the spread of HIV.
Individuals who are infected with STDs are at least two to five times more likely than uninfected individuals to acquire HIV infection if they are exposed to the virus through sexual contact, according to the CDC. Also, if an HIV-infected individual is infected with another STD, that person is more likely to transmit HIV through sexual contact than other HIV-infected persons.
Since STDs continue to be highly prevalent in many parts of the United States, the CDC has recommended that the early detection and treatment of curable STDs become a major component of comprehensive HIV prevention programs.
Abbott Diagnostics, Abbott Park, Ill, developed the first HIV antibody test in March 1985, approximately 5 years after the first glimpse of AIDS was seen in five men from Los Angeles. The test was an enzyme immunoassay (EIA or ELISA), a technically challenging technique that requires sophisticated lab equipment, used for the screening of donated blood.
As research into the deadly virus evolved, so did the diagnostic techniques, according to Catherine Brennan, PhD, a research fellow at Abbott. The gold standard is a two-pronged approach: a positive result from an ELISA antibody assay, followed by a western blot for confirmation. This is a complex test to administer.
Nucleic Acid Testing—The Gold Standard for HIV
Still in the vanguard of HIV diagnostics, Abbott developed the Prism HIV O Plus, which was approved by the FDA in September 2009 as a screening tool for the detection of certain antibodies to HIV. One of five assays that run on the fully automated Abbott Prism System, the assay is the first fully automated blood screening test for both HIV 1 and HIV 2, a newer subtype found mostly in West Africa. The assay runs on the ABBOTT PRISM system, which can run 160 samples per hour, making it possible to test more than 1,200 samples in an 8-hour shift. It is only the second donor screening test licensed for the detection of antibodies to HIV type 1, group O.
While antibody tests are accurate, they are not able to detect the HIV virus particle itself. According to Brennan, the trend the last several years has been to improve the sensitivity of diagnostic assays in order to detect infections early after exposure, before antibodies are even being produced. Molecular testing helps detect the actual RNA or DNA of the infectious agent in the blood.
“The idea is to reduce the time period between when infection is acquired and when a diagnostic assay is able to detect the infection,” Brennan says.
Nucleic acid tests (NATs) detect the viral nucleic acid and can identify an infection prior to seroconversion, or detectable antibodies, and are used in conjunction with antibody assays in high-risk populations, Brennan says. NATs are more specific and sensitive than immunoassays and use either transcription-mediated amplification or polymerase chain reaction (PCR). However, they are more expensive and technically sophisticated.
“There are several challenges facing labs,” Brennan says. “Some are assay specificity and sensitivity, or false positive and false negative results. Some traditional methods, such as western blot, are not as sensitive as the newer assays, but it can be challenging for labs to convert from older technologies to the newer technologies.”
The Cobas TaqScreen MPX Test nucleic acid test from Roche Molecular Diagnostics, Indianapolis, was approved in the United States last year as a qualitative, in vitro test for the simultaneous, direct detection of the human immunodeficiency virus (HIV-1 Group M RNA, HIV-1 Group O RNA, HIV-2 RNA), hepatitis C virus RNA and hepatitis B virus DNA in human plasma. For use on the fully automated, real-time PCR cobas s 201 system, it is a multiplex test for comprehensive single-assay detection. It has also been approved for screening of source plasma in pools comprised of up to 96 individual donations, and it is designed to increase processing efficiency with a unique modular design and ready-to-use reagents.
“Roche is committed to meeting the needs of blood centers with tests and systems that ensure the highest blood safety,” says Bryan Moore, PhD, group marketing manager for virology. “Our multiplex test has been widely adopted and has demonstrated excellent performance worldwide.”
Roche also manufactures the highly accurate Cobas AmpliPrep/Cobas TaqMan HIV-1 Test, the first fully automated HIV-1 diagnostic tool using real-time PCR technology in the United States. It provides a broader range of viral load data than earlier-generation tests, quantifying the amount of virus in the blood from very high to very low levels. With the test, labs can deliver highly accurate results faster, Moore says—a decisive advantage for physicians monitoring how well a chosen therapy is working for the patient.
Gen-Probe Inc, San Diego, offers the APTIMA HIV-1 RNA Qualitative Assay, the first FDA-approved NAT for diagnosis of HIV-1 infection in human plasma. The in vitro assay amplification targets the conserved regions in the long terminal repeat sequences of DNA and the RNA polymerase regions of the HIV-1 genome.
Gen-Probe also offers a NAT amplification test, the APTIMA COMBO 2 assay, to detect chlamydia and gonorrhea. Using an endocervical, urethral, or vaginal swab, the test is used in hospital and reference labs to provide results within several hours of the sample arriving in the laboratory.
Offering multiplex detection and differentiation, the test virtually eliminates inhibition problems and cross-reactivity while improving workflow and throughput.
QIAGEN Inc, Germantown, Md, offers the digene Human Papillomavirus (HPV) Test, also known by laboratories as the digene Hybrid Capture 2 (HC2) HPV DNA Test. The DNA test detects 13 clinically relevant high-risk HPV types from a cervical cell specimen and can be run from the same specimen vial as the liquid PAP smear test.
HPV testing identifies women with high-risk HPV infections that can cause cervical cancer, enabling diagnosis and treatment to be put in place before cervical cancer develops. Women whose immune systems are weakened by HIV/AIDS are more at risk of developing cervical disease from HPV.
The automated Rapid Capture System provides results in 1 day and can run 176 tests in 5 1/2 hours. Suitable for most lab skill levels, the system can adapt to most any workflow situation and can process small and large specimen batches cost-effectively. Based on QIAGEN’s proprietary HC2, used in labs that conform to CLIA guidelines, the technology uses probes that specifically target DNA from bacteria or viruses, such as chlamydia and gonorrhea.
If bacteria or a virus is present in the sampled cells, these probes find the target DNA when added to the sample and hybridize (bind) to it. These hybrids (target DNA bound by the probe) are then captured to allow detection through signal amplification. In this process, special antibodies and enzymes are added to the sample that—in the presence of captured hybrids—cause the emission of light that is measured by a computerized laboratory instrument.
Moving Toward the Point of Care
As with diagnostics for other conditions and diseases, HIV and STD testing is also moving toward rapid point-of-care testing.
“While the diagnostic markers for HIV are very accurate, there is still a lot of infection that goes undiagnosed,” says Stephen Lee, PhD, executive vice president and chief scientific officer for OraSure Technologies Inc, Bethlehem, Pa.
The stigma still attached to HIV prevents many from going to a center or clinic to be tested, and 30% of those who do go and get tested will not return for their results (typically available 2 or more weeks after the test), according to the CDC. The organization estimates that about one-fourth of the nearly 900,000 Americans in the United States with HIV do not know they are infected.
“Over the last few years, there has been an increase in the amount of rapid testing approved for HIV,” Lee says. “These tests provide results while the patient is still there and have contributed to the increase in the number of cases being diagnosed. They don’t require complex automation or shipping to labs, so they can be deployed right in the at-risk communities.”
In 2004, OraSure Technologies launched the OraQuick Advance Rapid HIV-1/2 Antibody Test for Oral Fluid. The test provides results in 20 minutes using oral fluid, plasma, or blood, which makes it ideal for both clinical and nonclinical settings, such as outreach programs and mobile testing clinics.
To perform an oral test, the tester takes the device that has an absorbent pad at one end, places the pad above a person’s teeth along the outer gum, and swabs once around both the upper and lower gums. The tester then inserts the device into a vial containing the developing solution.
“This test offers patients accurate HIV testing without the need for a needle,” Lee says. “Pain-free testing with oral fluid means more people get screened, more HIV-positive individuals get care, and fewer people are exposed.”
OraSure also manufactures the OraQuick® Rapid HCV Antibody Test for rapid detection of Hepatitis C (HCV), a virus that infects about one-fourth of HIV-infected individuals in the United States. Approved for use in Europe, the product is currently undergoing clinical trials in the United States. HCV is one of the most important causes of chronic liver disease in the nation, and HCV infection progresses more rapidly to liver damage in those infected with HIV. HCV infection may also impact the course and management of HIV.
AcroMetrix Corp, Benicia, Calif, offers several quality control materials for HIV tests such as some of those mentioned above, including the OptiQuant HIV-1 Quantification Panel; the ValiQuant HIV-1 Quantification Panel; and the OptiQual HIV-1 Low, Mid, and High Positive Controls.
For use with molecular NATs, the products are primarily used in hospital, clinical, and reference labs, as well as in blood banks, which use either FDA-approved products or are CLIA certified. The OptiQual HIV-1 High Control provides the highest concentration available for HIV-1 quality control material, monitoring the performance of the upper dynamic range of quantitative real-time HIV-1 NAT assays, while the low and mid controls ensure that the labs can detect for mid and low levels.
“Many labs need validation and verification,” says Romain Prieur, vice president of global marketing and business development at AcroMetrix. “They must look at all steps from sample preparation to detection to ensure that assays are acting properly. We provide materials to qualify these products.”
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Labs using FDA-approved products must verify that they are consistently able to quantify the varying levels of the virus, from low to high.
“HIV mutates quite rapidly, and there are a lot of drug-resistant forms,” says the company’s principal scientist, Mona Shahbazian. “We offer custom products that can verify that the labs can detect these HIV mutants.”
From AcroMetrix’s quality control products to the latest in molecular diagnostics, HIV and STD diagnostics continue to evolve and incorporate the latest in technology. In most cases, early diagnosis can mean the difference between life and death.
Shannon Rose is a freelance health and medical writer based in Temecula, Calif.