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

Disclosures

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

In This Article

Results

Method Correlation and Confirmation of HIV Infection

Concordance for HIV-infected samples between cobas HIV-1/2 Qual test and recomLine HIV-1 & HIV-2 IgG with plasma and serum samples was 100% for HIV-1 (302/302; 1 indeterminate test) and 99.7% for HIV-2 (301/302; Table 1). One result was indeterminate on recomLine HIV-1 & HIV-2 IgG and remained indeterminate on retesting. This sample showed negative result when retested in duplicate with Elecsys HIV combi PT fourth-generation test. Another sample was HIV-2–negative on cobas HIV-1/2 Qual test but HIV-2–positive on the recomLine HIV-1 & HIV-2 IgG. No HIV-2 sequence was obtained in sequencing analysis.

Comparison of cobas HIV-1/2 Qual test with the CAP/CTM showed 100% agreement for plasma samples (148/148; 68 HIV-1–positive and 80 HIV-1–negative). All 60 confirmed HIV-positive samples showed positive results with cobas HIV-1/2 Qual test, giving a sensitivity of 100%.

DBS samples from perinatally HIV-exposed children showed 99.6% agreement in cobas HIV-1/2 Qual test when compared with CAP/CTM (278/279). One sample showed a negative result for CAP/CTM, but positive results for cobas HIV-1/2 Qual test and for both heminested PCR and Post-PCR ultraperformance liquid chromatography. The overall sensitivity of the cobas HIV-1/2 Qual test was 100% (279/279) and specificity 99.3% (151/152).

Specificity

Four DBS samples showed positive results for HIV-1 on cobas HIV-1/2 Qual test. These were excluded after testing on heminested PCR, which confirmed that the samples were true HIV-1–positive specimens. All valid plasma (n = 613), serum (n = 607), and DBS samples (n = 604) tested HIV-negative with cobas HIV-1/2 Qual test. The specificity of cobas HIV-1/2 Qual test on each sample matrix was, thus, 100%, with a lower one-sided 95% confidence interval of 99.5% (Table 2).

Genotype Inclusivity

We observed test positivity rates of 100% for all HIV-1 and HIV-2 groups and subtypes tested in undiluted samples (Table 3). Similarly, 100% subtype inclusivity was demonstrated in dilutions with all subtypes at about 5xLOD, aside from HIV-1 group N. The one HIV-1 group N cultured isolate was detected in 4 replicates at several dilutions, including at about 3 × LOD, but was detected in only 50% of cases at a dilution substantially below the LOD.

Limits of Detection

The LOD determined using probit analysis for plasma LODs was 13 copies/mL for HIV-1 group M, 15 copies/mL for HIV-1 group O, and 28 copies/mL for HIV-2 (Table 4). The corresponding LODs for serum were 12, 13, and 23 copies/mL. The LOD in DBS for HIV-1 group M was 255 copies/mL and 984 copies/mL for HIV-2. The LOD determined by ≥95% hit rate on plasma and serum was 20 copies/mL for HIV-1 groups M and O and 360 copies/mL for DBS HIV-1 group M dilutions (for HIV-2 ≥95% hit rates, refer to Table 4). The 50% LOD estimation using probit analysis for plasma LODs was 2.9 copies/mL for HIV-1 group M, 3.4 copies/mL for HIV-1 group O, and 5.8 copies/mL for HIV-2 (Table 4). The corresponding 50% LODs for serum were 3.0, 2.8, and 6.1 copies/mL. The LOD in DBS for HIV-1 group M was 57.1 copies/mL and 227.3 copies/mL for HIV-2.

Performance on Seroconversion Panels

In the first assessment, consisting of 10 panels, a difference in days to first test positivity could not be determined in 4 cases because the Bio-Rad Geenius HIV 1/2 Confirmatory Assay remained negative at the last visit day (Figure 2). One panel member was excluded because its first day of detection varied considerably from the other panels, both on the certificate of analysis (day 97) and on HIV-1/2 Qual (day 127). In the remaining 5 panels, cobas HIV-1/2 Qual test detected HIV-1 a mean of 18.9 days earlier than the Bio-Rad Geenius HIV 1/2 Confirmatory Assay (Figure 2). The second assessment, testing of 25 panels, found that cobas HIV-1/2 Qual test detected HIV-1 a mean of 8.5 days earlier than the Abbott ARCHITECT HIV Ag/Ab Combo assay (Figure 3). Finally, in 20 of the 25 panels tested in the third assessment, the number of days to reactive result was identical in the cobas HIV-1/2 Qual test and cobas TaqScreen MPX, v2.0. The cobas HIV-1/2 Qual test detected HIV-1 earlier in 2 of the 25 panels by an average of 8 days and later in 3 panels by a mean of 3.3 days.

Figure 2.

HIV-1 seroconversion panel results comparing time to diagnosis with the cobas HIV-1/2 Qual test and Bio-Rad Geenius HIV 1/2 Confirmatory Assay.

Figure 3.

HIV-1 seroconversion panel results comparing time to diagnosis with the cobas HIV-1/2 Qual test and Abbott ARCHITECT HIV Ag/Ab Combo test.---Average difference in days to reactive (cobas vs ARCHITECT).

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