Early Diagnosis of HIV-1 and HIV-2 Using Cobas HIV-1/HIV-2 Qualitative Test

A Novel Qualitative Nucleic Acid Amplification Test for Plasma, Serum, and Dried Blood Spot Specimens

Lucia Hans, MB BCh, FCPath; Nicole von Allmen, PhD; Anke Edelmann, PhD; Jörg Hofmann, PhD; Alex Y. Nilsson, PhD; Christian O. Simon, PhD; Britta Seiverth, PhD; Peter Gohl, PhD; Sergio Carmona, PhD


J Acquir Immune Defic Syndr. 2021;87(5):1187-1195. 

In This Article


The cobas HIV-1/2 Qual test demonstrated excellent sensitivity, specificity, and genotype inclusivity for both HIV-1 and HIV-2 in plasma, serum, and DBS samples. The assay also detected HIV several weeks earlier than an HIV antibody test and a fourth-generation antibody/antigen test. Furthermore, correlation of the cobas HIV-1/2 Qual test with the recomLine HIV-1 & HIV-2 IgG and CAP/CTM showed more than 99% concordance across all sample types. No cross-reactivity with HIV-1 and HIV-2 was noted. In a few discordant samples, the results of cobas HIV-1/2 Qual test concurred with those of additional tests performed to resolve these discrepancies. We observed reactivity rates of 100% for all HIV-1 and HIV-2 genotypes in undiluted specimens from HIV-positive patients and in all dilutions above the LOD. The performance of the HIV cobas HIV-1/2 Qual test documented in this study suggests that the test is suitable for the second test on the CDC and WHO testing algorithm. Negative RNA samples can then be reflexed to the Geenius assay for final confirmation. Such decisions are based on cost, test availability, and laboratory capacity, among other factors.

Among adults, the ability of HIV cobas HIV-1/2 Qual test to detect HIV shortly after infection has considerable implications, both for the index patient and for their sexual or injecting drug partners.[3,4] Furthermore, oral preexposure prophylaxis to prevent HIV acquisition, and potentially injectable preexposure prophylaxis in future, presents major diagnostics concerns, especially the lengthy delays in seroconversion that may occur. Early diagnosis is important in people taking preexposure prophylaxis and before commencing prophylaxis because they may develop resistance to the antiretroviral drug if diagnosis is delayed. Tests in this context involving plasma, DBS, or even lysed whole blood need to have low LODs because the viral load levels may be low in these patients, given they are taking antiretroviral drugs. Moreover, timely diagnosis of HIV can reduce the risk of HIV transmission to infants by detecting new HIV infections in pregnant and breastfeeding women and can raise survival and minimize HIV-related morbidity in children who do acquire HIV.[33] Early diagnosis of HIV is also a central part of the care packages for individuals requiring HIV postexposure prophylaxis after sexual, occupational, or other exposures to HIV.[30] In addition, the assay could play an important role in detecting resistant virus and poor adherence in people receiving antiretroviral treatment.

The ability of the test to discriminate between HIV-1 and HIV-2 means that the cobas HIV-1/2 Qual assay has the potential to decrease the number of NATs needed in diagnostic algorithms that include HIV-1 and HIV-2. In addition, this feature of the assay may allow type discrimination to be extended beyond the countries where this is currently recommended. This would have major implications for people infected with HIV-2 who are currently undiagnosed in most settings and, as a consequence, receive suboptimal care.[20]

The study highlights several important evidence gaps in this field. A major concern relates to the accuracy of early infant diagnosis assays.[37] As rates of mother-to-child transmission of HIV decline, so does the positive predictive value of these assays. As many as 10% of infants who initiate treatment in settings with highly effective programs for preventing mother-to-child transmission may have false-positive diagnoses.[38] In 2018, WHO, thus, recommended the use of an "indeterminate range" in NAT tests as a means of optimizing the trade-off between the harms of incorrectly classifying an HIV-infected infant as indeterminate and the harms of starting treatment in HIV-uninfected infants.[37] Conversely, false-negative results are also highly worrisome among newborns, infants, and young children because antiretroviral drugs taken by the mother during pregnancy or breastfeeding or by the child may cause low-level viremia in infected children.[30,39,40] More broadly, the results of this study will need to be confirmed in field conditions.

In conclusion, the cobas HIV-1/2 Qual test is a CE-marked real-time PCR assay that identified acute HIV infection earlier than the fourth-generation tests and reliably differentiated between HIV-1 and HIV-2. The assay performed well on a range of sample types and in both adults and children. The test could be considered for inclusion in HIV testing guidelines in the United States and the European Union and in other settings where differentiation of HIV-1 and HIV-2 is currently recommended. Of note, the assay could simplify HIV diagnostic algorithms and expand access to NAT HIV testing for adults and children through the use of DBS samples. These features of the test mean that it could make a substantial contribution to reaching the "first 90" The Joint United Nations Programme on HIV/AIDS goal, the testing of 90% of the population.[2] Finally, earlier detection of HIV has important survival benefits for children and reduces HIV transmission among adults.