SHORT REPORT The performance of the Alere HIV combo point-of- care test on stored serum samples; useful for detection of early HIV-1 infections? Carla van Tienen, 1 Sharona Rugebregt, 1 Sandra Scherbeijn, 1 Hannelore Götz, 2,3 Corine GeurtsvanKessel 1 1 Department of Viroscience, Erasmus Medical Center, Rotterdam, The Netherlands 2 Department of STI Control and Sexual Health, Rotterdam- Rijnmond Public Health Service, Rotterdam, The Netherlands 3 Department of Public Health, Erasmus Medical Center, Rotterdam, The Netherlands Correspondence to Dr Carla van Tienen, Department of Viroscience, Erasmus Medical Center, Wytemaweg 80, Nb1052, Rotterdam 3015 CN, The Netherlands; c.vantienen@erasmusmc.nl; HG and CGvK contributed equally. Received 24 July 2016 Revised 8 December 2016 Accepted 10 December 2016 To cite: van Tienen C, Rugebregt S, Scherbeijn S, et al. Sex Transm Infect Published Online First: [ please include Day Month Year] doi:10.1136/sextrans- 2016-052818 ABSTRACT Introduction The Alere HIV-1/2 Antigen/Antibody Combo point-of-care test is a commercially available 4th- generation rapid test for the diagnosis of HIV infection, including acute infection. We evaluated the sensitivity of this test in samples from patients with acute, recent or chronic HIV-1 infection. Methods A validation of the test was performed using 89 HIV-positive serum samples collected in 2008–2016, that were stored at -20°C. Twenty-three samples were only p24-positive (acute infection); 49 samples were antibody-positive and p24-positive (recent infection); 17 samples were only antibody-positive (chronic infection). HIV infection was confirmed by standard-of-care assays and PCR. Samples came from patients attending an outpatient clinic for STDs at the Public Health Department and from patients within the Erasmus Medical Center, Rotterdam, the Netherlands. Results The overall sensitivity of the test for diagnosing HIV infection based on detection of p24 antigen and/or antibodies was 92% (95% CI 86% to 98%) (82/89). In acute sera with only p24 antigen positivity, the sensitivity of the test decreased to 65% (95% CI 46% to 85%) (15/23). When both antibody and antigen testing were positive, the p24 sensitivity was only 24% (95% CI 12% to 36%) (12/49), but in these sera the final test result was positive in all sera (49/49) due to the positive antibody component. Conclusions In a laboratory setting, this test has an overall sensitivity of 92% to detect any stage of HIV-1 infection using sera specimens. It performs relatively well in detecting early HIV and may be beneficial as an initial screening in patients with a recent exposure to HIV. Additional testing in a laboratory setting remains mandatory as a proportion of acute HIV-1 infections are missed with this test. INTRODUCTION Rapid tests or point-of-care tests (POCTs) for detection of HIV-1 are often used in clinical prac- tice in persons who have a high risk of HIV infec- tion because they give a quick result, can improve the uptake of HIV testing, enable rapid follow-up testing and are relatively cheap. They are used at our Public Health STI clinic, in persons at high risk for HIV, specifically men who have sex with men or those notified for HIV. The results of the POCT are always confirmed by a second routine fourth- generation laboratory test. During acute HIV-1 infection, p24 antigen can be detected in serum while antibodies titres are still undetectable. Acute HIV-1 infections are important to diagnose because an early start of treatment improves the outcome of the infection in the individual and because it pre- vents transmission to others. 1 The latest (fourth) generation POCTs can detect and differentiate anti- bodies and p24 antigen in sera and thereby aim to reduce the window period. The Alere HIV-1/2 Ag/Ab Combo rapid test (Combo RT, Alere Medical) is a novel fourth-generation test which can be used on serum, plasma and whole blood specimens and has a turnaround time of 20 min. A recent paper by Fitzgerald et al in this journal describes a high sensitivity (88%) of this test in sera with detectable p24 antigen. Unfortunately it does not report specifically on the sensitivity in case anti- bodies are present besides the p24 antigen, which is more often the case in screening. 2 The previous fourth-generation HIV POCT, the Alere HIV-1/2 Ag/Ab Determine, showed a varying sensitivity for acute infections with only p24 antigen. Reported sensitivities varied from 0% (0/2 samples; 3 0/8, 4 ), 0% (0/13, 5 ), 3% (1/34, 6 ), 23% (13/57, 7 ), 50% (3/6, 8 ), 54% (14/26 9 ) to 67% (26/39 10 ). We investigated whether the new Alere Combo POCT is able to detect p24 antigen with or without antibodies (as found in acute or recent HIV infection) in HIV-1 infections in samples from the Public Health STI Clinic and the Erasmus Medical Center (MC) in Rotterdam. METHODS Study design The validation of Combo POCT was performed on retrospectively collected samples. Study participants Eighty-nine anonymised samples were tested from patients attending an STI clinic at the Public Health Centre and from patients within the Erasmus MC in Rotterdam, the Netherlands. Samples The sera were collected in 2008–2016 and stored at -20°C. Twenty-three samples were only p24-positive; 49 samples were both antibody- positive and p24-positive and 17 samples were only antibody-positive. Follow-up samples were available from 14 patients. van Tienen C, et al. Sex Transm Infect 2017;0:1–3. doi:10.1136/sextrans-2016-052818 1 Clinical STI Online First, published on January 19, 2017 as 10.1136/sextrans-2016-052818 Copyright Article author (or their employer) 2017. Produced by BMJ Publishing Group Ltd under licence.