The current HIV diagnostic algorithm (published in 1989) consists of a repeatedly reactive HIV immunoassay followed by a supplemental test for confirmation, such as the Western blot or indirect immunofluorescence assay (IFA) [1x[1]Centers for Disease C. Interpretation and use of the Western blot assay for serodiagnosis of human immunodeficiency virus type 1 infections. MMWR. Morbidity and Mortality Weekly Report. 1989; 38: 1–7

See all References][1]. Early HIV immunoassays used either viral lysate antigens (first generation) or synthetic peptides and recombinant antigens (second generation) and detected only immunoglobulin G (IgG)-class antibodies. Most laboratories now use either third-generation immunoassays that detect both IgM-class and IgG-class antibodies or fourth-generation combination antigen/antibody immunoassays that detect both classes of antibody and also p24 antigen (a major core protein of HIV). IgM-class antibody and p24 antigen can be detected early, before IgG-class antibody appears, decreasing the window period between time of infection and the time that infection can be detected by screening [2x[2]Owen, S.M., Yang, C., Spira, T., Ou, C.Y., Pau, C.P., Parekh, B.S. et al. Alternative algorithms for human immunodeficiency virus infection diagnosis using tests that are licensed in the United States. Journal of Clinical Microbiology. 2008; 46: 1588–1595

CrossRef | PubMed | Scopus (82)See all References][2]. Additionally, these newer HIV immunoassays detect antibodies to HIV-2 in addition to HIV-1, but are unable to differentiate them from HIV-1 antibodies. Although these advances have occurred with screening immunoassays, the supplemental testing options available in the U.S., Western blot and IFA, have remained the same: both are unable to detect IgM-class antibody and p24 antigen and are unable to reliably detect (or differentiate) HIV-2 antibody [[3]x[3]Centers for Disease C. Prevention. HIV-2 Infection Surveillance—United States, 1987–2009. MMWR. Morbidity and mortality weekly report. 2011; 60: 985–988

PubMedSee all References, [4]x[4]Pau, C.P., Granade, T.C., Parekh, B., Schochetman, G., DeCock, K.M., Gayle, H. et al. Misidentification of HIV-2 proteins by Western blots. Lancet. 1991; 337: 616–617

Abstract | PubMed | Scopus (4)See all References]. To improve HIV diagnosis, a new HIV diagnostic testing algorithm has been proposed [[5]x[5]Pandori, M.W. and Branson, B.M. 2010 HIV diagnostics conference. Expert Review of Anti-Infective Therapy. 2010; 8: 631–633

CrossRef | PubMed | Scopus (30)See all References, [6]x[6]CLSI. Criteria for Laboratory Testing and Diagnosis of Human Immunodeficiency Virus Infection; Approved Guideline. Clinical and Laboratory Standards Institute, Wayne, PA; 2011

See all References, [7]x[7]Centers for Disease C. Prevention. Detection of Acute HIV Infection in Two Evaluations of a New HIV Diagnostic Testing Algorithm – United States, 2011–2013. MMWR. Morbidity and Mortality Weekly Report. 2013; 62: 489–494

PubMedSee all References]. The new diagnostic algorithm evaluated in this study replaces the WB with an HIV-1/HIV-2 antibody differentiation assay as the supplemental test and includes an RNA test to resolve reactive immunoassay with negative supplemental test results [[5]x[5]Pandori, M.W. and Branson, B.M. 2010 HIV diagnostics conference. Expert Review of Anti-Infective Therapy. 2010; 8: 631–633

CrossRef | PubMed | Scopus (30)See all References, [6]x[6]CLSI. Criteria for Laboratory Testing and Diagnosis of Human Immunodeficiency Virus Infection; Approved Guideline. Clinical and Laboratory Standards Institute, Wayne, PA; 2011

See all References, [7]x[7]Centers for Disease C. Prevention. Detection of Acute HIV Infection in Two Evaluations of a New HIV Diagnostic Testing Algorithm – United States, 2011–2013. MMWR. Morbidity and Mortality Weekly Report. 2013; 62: 489–494

PubMedSee all References, [8]x[8]Branson, B.M. and Mermin, J. Establishing the diagnosis of HIV infection: new tests and a new algorithm for the United States. Journal of Clinical Virology: The Official Publication of the Pan American Society for Clinical Virology. 2011; 52: S3–S4

Abstract | Full Text | Full Text PDF | PubMed | Scopus (19)See all References]. In retrospective studies, this algorithm can be performed more rapidly than the current HIV diagnostic algorithm, can detect acute HIV-1 infections, and can diagnose unsuspected HIV-2 infections [[7]x[7]Centers for Disease C. Prevention. Detection of Acute HIV Infection in Two Evaluations of a New HIV Diagnostic Testing Algorithm – United States, 2011–2013. MMWR. Morbidity and Mortality Weekly Report. 2013; 62: 489–494

PubMedSee all References, [9]x[9]Nasrullah, M., Wesolowski, L.G., Meyer, W.A. 3rd, Owen, S.M., Masciotra, S., Vorwald, C. et al. Performance of a fourth-generation HIV screening assay and an alternative HIV diagnostic testing algorithm. AIDS (London, England). 2012;

See all References]. As of March 25, 2013 in the U.S., the Multispot HIV-1/HIV-2 Rapid Test (Multispot) is FDA-approved as the second test (after a repeatedly reactive HIV immunoassay) to diagnose HIV infection as part of a testing algorithm [10x[10]Multispot HIV-1/HIV-2 Rapid Test. Package Insert. ; 2013 (Available from:)http://www.bio-rad.com/en-us/product/retrovirus-hiv-mdash-rapid-test/multispot-hiv-1-hiv-2-rapid-test. ([accessed 12.07.13])

See all References][10]. Multispot consists of a single-use, flow-through cartridge whereupon a rapid immunoassay is performed on a filter substrate. The assay is a rapid (∼15 min) qualitative immunoconcentrating assay that detects and differentiates antibody against HIV-1 and HIV-2 in serum or plasma. Two “spots” on the filter consist of recombinant HIV-1 gp41 and a peptide containing an immunodominant epitope of HIV-1 gp41, respectively. A third spot consists of a peptide containing an immunodominant epitope of HIV-2 gp36. A fourth spot consists of goat anti-human IgG, which serves as a methodological control [10x[10]Multispot HIV-1/HIV-2 Rapid Test. Package Insert. ; 2013 (Available from:)http://www.bio-rad.com/en-us/product/retrovirus-hiv-mdash-rapid-test/multispot-hiv-1-hiv-2-rapid-test. ([accessed 12.07.13])

See all References][10]. Given the importance of Multispot in the new HIV diagnostic algorithm, we compared the performance of this assay as a supplemental test after a repeatedly reactive immunoassay result with the performance of Western blot and IFA.

The Screening Targeted Populations to Interrupt On-going Chains of HIV Transmission with Enhanced Partner Notification (STOP) study is a prospective, on-going study evaluating: (1) methods to detect acute HIV infection and enhance partner services in New York City, North Carolina, and San Francisco, California; and (2) the new HIV diagnostic algorithm. The STOP study was approved by institutional review boards for the University of California at San Francisco, the University of North Carolina at Chapel Hill, and the New York City Department of Health & Mental Hygiene, and by a research determination at CDC. Participants were ≥12 years of age and receiving HIV testing at one of 12 HIV testing venues in sexually transmitted infection clinics and community-based HIV testing programs. Specimens collected between September 1, 2011 and September 1, 2012 were included in this analysis. Data on the frequency of acute HIV infections detecting during the STOP study have been published elsewhere [7x[7]Centers for Disease C. Prevention. Detection of Acute HIV Infection in Two Evaluations of a New HIV Diagnostic Testing Algorithm – United States, 2011–2013. MMWR. Morbidity and Mortality Weekly Report. 2013; 62: 489–494

PubMedSee all References][7] but this manuscript is the first evaluation of the performance of Multispot compared with both Western blot and IFA in the STOP study.

Specimens were screened with the Architect HIV Ag/Ab Combo Assay (Architect; Abbott Diagnostics, Abbott Park, IL), a fourth-generation immunoassay, according to manufacturer's specifications. Repeatedly reactive specimens were tested with the Multispot HIV-1/HIV-2 Rapid Test (Multispot; Bio-Rad Laboratories, Redmond, WA) and either an HIV-1 Western blot (Bio-Rad Laboratories) at the New York City and North Carolina testing sites or an IFA (Sanochemia, Vienna, Austria) at the San Francisco testing site, per package insert. Specimens with negative Multispot, Western blot or IFA results (discordant screening and confirmatory results) were tested for HIV-1 RNA with either Aptima HIV-1 RNA Qualitative Assay (Aptima; Gen-Probe, Inc., San Diego, CA), a qualitative method of HIV-1 RNA detection with a lower limit of detection of approximately 30 copies per ml plasma, or m2000 RealTime HIV-1 Quantitative Assay (Abbott Diagnostics), a quantitative test with a lower limit of quantification of 40 copies per ml plasma [11x[11]Ren, A., Louie, B., Rauch, L., Castro, L., Liska, S., Klausner, J.D. et al. Screening and confirmation of human immunodeficiency virus type 1 infection solely by detection of RNA. Journal of Medical Microbiology. 2008; 57: 1228–1233

CrossRef | PubMed | Scopus (7)See all References][11].

Multispot results were determined according to the manufacturer's new specifications [10x[10]Multispot HIV-1/HIV-2 Rapid Test. Package Insert. ; 2013 (Available from:)http://www.bio-rad.com/en-us/product/retrovirus-hiv-mdash-rapid-test/multispot-hiv-1-hiv-2-rapid-test. ([accessed 12.07.13])

See all References][10]. The differentiation assay has four reaction spots including control, HIV-2 peptide, recombinant HIV-1, and HIV-1 peptide. Test results that did not develop a color reaction at the control spot were interpreted as invalid. Specimens with both HIV-1 spots (recombinant and peptide) reactive were interpreted as HIV-1 reactive. Specimens with only one HIV-1 spot (either recombinant or peptide) reactive were interpreted as HIV-1 indeterminate. Specimens with a reactive HIV-2 spot were interpreted as HIV-2 reactive. Specimens with both HIV-1 and HIV-2 spots reactive that could not be resolved with dilutional testing were interpreted as HIV antibodies detected (undifferentiated). Finally specimens with only a reactive control spot were interpreted as negative for HIV-1 and HIV-2 antibodies.

The primary analysis described and compared the frequencies of Multispot, Western blot, and IFA results among participants with repeatedly reactive fourth-generation immunoassay results. All analyses were performed using SAS version 9.3 (SAS Institute Inc., Cary, NC, USA). McNemar's exact test was used to test for differences in proportions (categorical variables) between the tests. Statistical significance was indicated by a p-value <0.05.

From September 1, 2011 to September 1, 2012, 37,876 participants were screened with the Architect fourth-generation immunoassay at 12 testing venues. Overall, 654 (1.7%) specimens were found to be repeatedly reactive (positive) and were tested with Multispot (Fig. 1Fig. 1). No Multispot results were invalid. Multispot was reactive for both HIV-1 specific spots (HIV-1 Reactive) in 84.7% (554/654) of specimens. The recombinant gp41 spot (HIV-1) was solely reactive in 0.92% (6/654) and the gp41 peptide spot (HIV-1) was solely reactive for 0.46% (3/654) of specimens. There was one specimen (0.2%) with both HIV-1 spots and the HIV-2 spot reactive despite repeat testing at a 1:10 dilution and a 1:100 dilution as specified in the product insert; these results were interpreted as HIV antibody detected but undifferentiated.²2

Fig. 1

Multispot rapid HIV-1/HIV-2 differentiation assay results with the new HIV diagnostic testing algorithm – New York, San Francisco, and North Carolina, September 2011–2012.

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The nine Multispot HIV-1 indeterminate specimens (6 with the recombinant gp41 spot only and 3 with the gp41 peptide spot only) were tested for HIV-1 RNA. Of these, 8/9 (88.9%) had detectable HIV-1 RNA. The one specimen without detectable HIV-1 RNA was also negative by Western blot. This participant was retested one week later and on repeat testing had a negative Architect fourth-generation immunoassay result and undetectable HIV-1 RNA.

On initial Multispot testing, 19 (2.9%) specimens had both HIV-1 spots and the HIV-2 spot reactive consistent with a result positive for HIV antibodies, but undifferentiated for HIV-1 and HIV-2. After a 1:10 dilution, 17 of these specimens were found to be reactive for both HIV-1 spots but HIV-2 non-reactive. After a 1:100 dilution, one further specimen resolved to reactive for both HIV-1 spots but HIV-2 non-reactive. HIV-1 Western blot was performed on 13 of the 18 specimens that resolved by dilution and all 13 were HIV-1 positive (100%). IFA was performed on the other five specimens that resolved with dilution and all five were HIV-1 positive by IFA (100%). The one specimen that was not differentiated by either 1:10 or 1:100 dilutions was found to be HIV-1 Western blot positive, HIV-1 RNA detectable, HIV-2-specific immunoassay reactive, and HIV-2 Western blot positive consistent with a potential dual HIV-1/HIV-2 infection.

Overall 90 (13.8%) of the 654 Architect fourth-generation immunoassay reactive specimens were non-reactive by Multispot. Of these, 47/90 (52.2%) had detectable HIV-1 RNA consistent with an acute HIV-1 infection and 43 (47.8%) did not have detectable HIV-1 RNA consistent with a false-positive HIV screening test. These acute HIV infections accounted for 7.7% of the 610 HIV infections that could be confirmed by either Multispot or HIV-1 RNA testing (Fig. 1Fig. 1). Among these 47 specimens with detectable HIV-1 RNA, 22 were tested by Western blot of which two (9.1%) were positive, five (22.7%) were indeterminate, and 15 (68%) were negative. The other 25 specimens with detectable HIV-1 RNA were tested with IFA of which two were positive, one (4.0%) was indeterminate, and 22 were negative. Overall, 43 of 47 (91.5%) specimens were negative or indeterminate by Multispot and either Western blot or IFA despite having detectable HIV-1 RNA.

By combining Multispot and HIV-1 RNA results, 610 (93.3%) of 654 Architect fourth-generation immunoassay reactive specimens were confirmed to be consistent with HIV infection. Of these 610 specimens, 429 were tested by Western blot and Multispot and 181 were tested by IFA and Multispot (Table 1Table 1). Among the 429 specimens tested by Western blot, Multispot confirmed infection in 402³3

Among the 181 specimens tested by IFA, Multispot confirmed infection in 153 (84.5%; 95% confidence intervals [CI]: 79.3–89.8%) cases while the IFA confirmed infection in 151 (83.4%; 95% CI: 78.0–88.8%) cases (p = 0.75 by exact McNemar's test). Multispot and IFA were concordant in 93.9% of cases. Among Multispot HIV-1 reactive specimens (n = 153), there was one (0.7%) IFA-negative result. Among IFA-positive specimens (n = 151), there were two (1.3%) Multispot-negative results. Among these confirmed HIV infections (n = 181), Multispot and IFA also had similar frequencies of negative (n = 25 vs. n = 23 respectively) and indeterminate (n = 3 vs. n = 7 respectively) results.

Since 1989, the Western blot and IFA have been the recommended supplemental antibody tests for confirming reactive HIV immunoassay test results [1x[1]Centers for Disease C. Interpretation and use of the Western blot assay for serodiagnosis of human immunodeficiency virus type 1 infections. MMWR. Morbidity and Mortality Weekly Report. 1989; 38: 1–7

See all References][1]. On March 25, 2013, the Food and Drug Administration (FDA) approved a modification of the package insert for the Multispot HIV-1/HIV-2 Rapid Test so that it can be used as the second test (after a repeatedly reactive HIV immunoassay) to diagnose HIV infection as part of a testing algorithm⁴4

The new HIV diagnostic algorithm which was evaluated in this study replaces the Western blot with an HIV-1/HIV-2 antibody differentiation assay (Multispot) as the supplemental test and includes an HIV-1 RNA test to resolve reactive immunoassay with negative supplemental test results [[5]x[5]Pandori, M.W. and Branson, B.M. 2010 HIV diagnostics conference. Expert Review of Anti-Infective Therapy. 2010; 8: 631–633

CrossRef | PubMed | Scopus (30)See all References, [6]x[6]CLSI. Criteria for Laboratory Testing and Diagnosis of Human Immunodeficiency Virus Infection; Approved Guideline. Clinical and Laboratory Standards Institute, Wayne, PA; 2011

See all References, [7]x[7]Centers for Disease C. Prevention. Detection of Acute HIV Infection in Two Evaluations of a New HIV Diagnostic Testing Algorithm – United States, 2011–2013. MMWR. Morbidity and Mortality Weekly Report. 2013; 62: 489–494

PubMedSee all References, [8]x[8]Branson, B.M. and Mermin, J. Establishing the diagnosis of HIV infection: new tests and a new algorithm for the United States. Journal of Clinical Virology: The Official Publication of the Pan American Society for Clinical Virology. 2011; 52: S3–S4

Abstract | Full Text | Full Text PDF | PubMed | Scopus (19)See all References]. The advantages of this multi-test algorithm over the use of Western blot or IFA only as the supplemental test after a reactive immunoassay include that it can detect acute HIV-1 infections and can diagnose unsuspected HIV-2 infections [[7]x[7]Centers for Disease C. Prevention. Detection of Acute HIV Infection in Two Evaluations of a New HIV Diagnostic Testing Algorithm – United States, 2011–2013. MMWR. Morbidity and Mortality Weekly Report. 2013; 62: 489–494

PubMedSee all References, [9]x[9]Nasrullah, M., Wesolowski, L.G., Meyer, W.A. 3rd, Owen, S.M., Masciotra, S., Vorwald, C. et al. Performance of a fourth-generation HIV screening assay and an alternative HIV diagnostic testing algorithm. AIDS (London, England). 2012;

See all References]. In addition, the fast turnaround time for test results from the Multispot rapid test (15 min) affords the opportunity to deliver same-day definitive test results to the majority of HIV-infected persons who are antibody-positive. Although these advantages are significant, it is also important that Multispot does not sacrifice sensitivity for detecting HIV-1 antibody compared with Western blot and IFA. Data from this analysis indicates that Multispot's sensitivity is similar to both the Western blot and IFA. These results are consistent with previous studies comparing Multispot and Western blot. [[9]x[9]Nasrullah, M., Wesolowski, L.G., Meyer, W.A. 3rd, Owen, S.M., Masciotra, S., Vorwald, C. et al. Performance of a fourth-generation HIV screening assay and an alternative HIV diagnostic testing algorithm. AIDS (London, England). 2012;

See all References, [12]x[12]Styer, L.M., Sullivan, T.J., and Parker, M.M. Evaluation of an alternative supplemental testing strategy for HIV diagnosis by retrospective analysis of clinical HIV testing data. Journal of Clinical Virology: The Official Publication of the Pan American Society for Clinical Virology. 2011; 52: S35–S40

Abstract | Full Text | Full Text PDF | PubMed | Scopus (19)See all References, [13]x[13]Masciotra, S., McDougal, J.S., Feldman, J., Sprinkle, P., Wesolowski, L., and Owen, S.M. Evaluation of an alternative HIV diagnostic algorithm using specimens from seroconversion panels and persons with established HIV infections. Journal of Clinical Virology: The Official Publication of the Pan American Society for Clinical Virology. 2011; 52: S17–S22

Abstract | Full Text | Full Text PDF | PubMed | Scopus (47)See all References] While these previous studies also demonstrated the ability of Multispot to accurately confirm HIV infection they did not include a comparison of Multispot to IFA.

The most important performance characteristic of a supplemental test in a multi-test algorithm is specificity. In this analysis none of the Multispot results that were reactive for HIV-1 antibodies were determined to be false-positive suggesting that Multispot has similar specificity to Western blot and IFA (these assays also had no false-positive results). One Multispot HIV-1 indeterminate result, however, was determined to be negative for HIV infection. This specimen was positive for only one of two HIV-1 specific spots, the gp41 peptide spot. As per the new HIV diagnostic algorithm and the FDA-approved package insert, HIV-1 indeterminate results are tested for HIV-1 RNA [10x[10]Multispot HIV-1/HIV-2 Rapid Test. Package Insert. ; 2013 (Available from:)http://www.bio-rad.com/en-us/product/retrovirus-hiv-mdash-rapid-test/multispot-hiv-1-hiv-2-rapid-test. ([accessed 12.07.13])

See all References][10]. The false-reactive HIV-1 indeterminate result that was observed in this study validates this recommendation for HIV-1 RNA testing in these indeterminate situations.

While the performance characteristics of Multispot as a supplemental test was similar to both Western blot and IFA, it is important to highlight that none of these three supplemental tests were capable of confirming all of the HIV infections diagnosed in this study. Fourth-generation HIV immunoassays detect p24 antigen (in addition to IgG- and IgM-classes of antibody) which becomes detectable early during HIV infection, before antibody appears, allowing the fourth-generation immunoassays to identify some HIV infections in the acute phase [[7]x[7]Centers for Disease C. Prevention. Detection of Acute HIV Infection in Two Evaluations of a New HIV Diagnostic Testing Algorithm – United States, 2011–2013. MMWR. Morbidity and Mortality Weekly Report. 2013; 62: 489–494

PubMedSee all References, [13]x[13]Masciotra, S., McDougal, J.S., Feldman, J., Sprinkle, P., Wesolowski, L., and Owen, S.M. Evaluation of an alternative HIV diagnostic algorithm using specimens from seroconversion panels and persons with established HIV infections. Journal of Clinical Virology: The Official Publication of the Pan American Society for Clinical Virology. 2011; 52: S17–S22

Abstract | Full Text | Full Text PDF | PubMed | Scopus (47)See all References, [14]x[14]Pandori, M.W., Hackett, J. Jr., Louie, B., Vallari, A., Dowling, T., Liska, S. et al. Assessment of the ability of a fourth-generation immunoassay for human immunodeficiency virus (HIV) antibody and p24 antigen to detect both acute and recent HIV infections in a high-risk setting. Journal of Clinical Microbiology. 2009; 47: 2639–2642

CrossRef | PubMed | Scopus (59)See all References]. In this study, approximately half of the Multispot-negative specimens had detectable HIV-1 RNA consistent with acute HIV infection. Although some studies have suggested that Multispot is more sensitive for recent infection than the Western blot, perhaps due to the fact that a higher volume of serum or plasma is analyzed by the test [[2]x[2]Owen, S.M., Yang, C., Spira, T., Ou, C.Y., Pau, C.P., Parekh, B.S. et al. Alternative algorithms for human immunodeficiency virus infection diagnosis using tests that are licensed in the United States. Journal of Clinical Microbiology. 2008; 46: 1588–1595

CrossRef | PubMed | Scopus (82)See all References, [15]x[15]Louie, B., Wong, E., Klausner, J.D., Liska, S., Hecht, F., Dowling, T. et al. Assessment of rapid tests for detection of human immunodeficiency virus-specific antibodies in recently infected individuals. Journal of Clinical Microbiology. 2008; 46: 1494–1497

CrossRef | PubMed | Scopus (26)See all References], we did not observe an advantage in this study. Overall, these results underscore the importance of using a multi-test algorithm where discordant screening (reactive) and supplemental (negative) test results can be resolved with HIV-1 RNA testing. The detection of acute infection depends upon including HIV-1 RNA testing and is particularly important as this highly infectious phase contributes disproportionately to HIV transmission [[16]x[16]Pilcher, C.D., Joaki, G., Hoffman, I.F., Martinson, F.E., Mapange, C., Stewart, P.W. et al. Amplified transmission of HIV-1: comparison of HIV-1 concentrations in semen and blood during acute and chronic infection. AIDS (London, England). 2007; 21: 1723–1730

CrossRef | PubMed | Scopus (148)See all References, [17]x[17]Pinkerton, S.D. Probability of HIV transmission during acute infection in Rakai, Uganda. AIDS and Behavior. 2008; 12: 677–684

CrossRef | PubMed | Scopus (53)See all References].

The findings in this study are subject to at least two limitations. First, only one potential HIV-2 infection was detected which limited our ability to evaluate the impact of HIV-2 diagnosis in this comparison. Second, participants in the STOP study were a convenience sample of persons at high risk for HIV infection and a high frequency of acute HIV infections was detected. Although this relatively high prevalence of acute HIV infections should not affect the comparison of Multispot with Western blot and IFA, it is important for clinicians to realize that negative Multispot results may not correlate with acute HIV infections as frequently in low prevalence settings.

Multispot is an important diagnostic advance that differentiates between HIV-1 and HIV-2 infections and improves the timeliness of HIV testing. Multispot can be used as a supplemental test (the second test) in the new HIV diagnostic algorithm. In this prospective study, Multispot confirmed a comparable proportion of HIV infections and was highly concordant with the Western blot and IFA. This study also demonstrated that discordant screening (reactive) and confirmatory (negative) results occur with all of the supplemental assays and that HIV-1 RNA testing is necessary in these situations to detect acute HIV-1 infections.

CDC STOP project.

The authors of this manuscript do not possess any conflicts of interest with regard to manufacturers of the tests included.

None declared.