Diagnostics & Imaging Week

Laboratory Corporation of America Holdings (LabCorp; Burlington, North Carolina) has introduced an enhanced HIV Screening Assay to identify individuals with primary HIV infection.

Primary or acute HIV infection is that period following recent infection when an individual has not yet developed detectable levels of HIV antibodies. During this window period, infected individuals are considered significant contributors to the spread of HIV as they tend to have very high levels of the HIV virus, are very infectious, and are often not aware of their HIV status, the company said.

LabCorp’s enhanced HIV Screening Assay provides for automatic HIV nucleic acid testing (NAT) on antibody-negative samples utilizing a proprietary pooling method.

“They did pooled tests that had tested negative for the antibody, but when they did the direct tests looking for the actual presence of the virus using the pooled method, they uncovered additional cases of HIV that they consider to be in the acute stage, which is before the antibodies even develop,” LabCorp spokeswoman Pam Sherry told Diagnostics & Imaging Week.

Sherry said that LabCorp has a “long focus on doing this type of work on infectious disease already.” For example, she said that LabCorp was the first commercial laboratory to offer HIV drug resistance testing, “which helps doctors understand the original strain of virus and select drugs that are more likely to be effective.”

LabCorp, she said, has a “proprietary method to actually pool samples and do this nucleic acid testing” through its National Genetics Institute (NGI; Los Angeles).

“Mounting data suggest that a significant proportion of HIV transmissions occur during this highly viremic, acute stage of infection,” Myla Lai-Goldman, MD, LabCorp executive vice president, chief scientific officer and medical director, said in a company statement.

She added: “There are nearly 1 million people in the U.S. infected with HIV, with approximately 40,000 new infections each year. Earlier diagnosis leads to earlier referral for appropriate care and preservation of health. And, increased awareness of infection status combined with appropriate preventive counseling may significantly reduce the unknowing spread of infection.”

The company said evidence is building that combining antibody screening with HIV NAT using pooled samples can be an effective way to identify primary HIV infection.

A one-year pilot study conducted by the University of North Carolina (UNC; Chapel Hill) in collaboration with the North Carolina Department of Health and Human Services (NC Study) showed that testing HIV serologically negative individuals using NAT can help in the early identification of primary HIV infection. The NC Study performed NAT in pools of 90 samples on more than 100,000 HIV serologically negative samples tested by the state, with a positivity rate of approximately one in 5,000 screened samples.

Through its National Genetics Institute, LabCorp has the capability of pooled nucleic acid amplification with an HIV antibody screen. NGI’s laboratory is FDA approved to perform pooled-sample nucleic acid testing for screening plasma donors. Although LabCorp’s new HIV Screening assay is not FDA-cleared for diagnosing HIV infection, NGI performs the same NAT protocol for pooled HIV antibody- negative clinical samples as it uses for plasma products.

Sherry said that with its method, LabCorp can take serum from up to 512 individuals and test them at one time.

“If anything turns up positive, then we can do additional testing and isolate which of those samples were the samples that came up reactive,” she said. “And then we can isolate it down to the individual samples.”

Patients who are interested in getting the test should go to their physician and request it.

And while there may be public health departments that are doing similar testing, Sherry told D&IW that she was not aware of any other commercial or independent laboratory that is doing this type of NAT testing for primary HIV infections.

LabCorp, which has more than 220,000 clients, offers clinical assays ranging from blood analyses to HIV and genomic testing. Its clients include physicians, government agencies, managed care organizations, hospitals, clinical labs and pharmaceutical companies.