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HIV-2 during seroconversion
ELSEVIER
Clinical and Diagnostic Virology 7 (1996) 55-61
Clinical and Diagnostic Virology
Comparison of the sensitivity of four rapid assays for the detection of antibodies to HIV-1/HIV-2 during seroconversion Helvi H. Samdal a,*, Bjorg-Guri Gutigard a, Dolores Labay a, Sissel I. Wiik a, Kjell Skaug a, Anne G. Skar b ~Department of Virology, National Institute of Public Health, Postboks 4404 Torshov, N.0403 Oslo, Norway bDepartment of Microbiology, Ullev~l University Hospital, N-0407 Oslo, Norway
Abstract
Objectives: To compare the sensitivity of four rapid assays for the detection of antibodies against HIV-1 during early seroconversion. Methods: Four rapid assays for the detection of antibodies to HIV-1/HIV-2 (SUDS ® HIV 1 + 2, TestPack ® HIV-1/HIV-2, HIV-SPOT and CAPILLUS ® HIV-1/HIV-2) were evaluated on 38 sera derived from 14 HIV-1 seroconverters, formerly tested with Abbott second- and third-generation HIV-1/HIV-2 enzyme immunoassay (EIA) and Diagnostic Biotechnology HIV blot 2.2. EIA-negative sera had also been investigated by HIV-1 antigen testing and polymerase chain reaction (PCR) analysis detecting HIV-1 proviral DNA. Results: On 16 sera which were Abbott second-generation EIA negative, the SUDS assay rated highest with six positive results. Four sera were TestPack positive. No specimens in this group were HIV-SPOT positive or CAPILLUS positive. Of the remaining 22 sera (Abbott second- and third-generation EIA positive), all but two were positive in all tests. Conclusions: The study revealed differences in the sensitivities of the rapid assays in the early phase of seroconversion. The most sensitive assay, SUDS, was even more sensitive than the Abbott third-generation EIA, while TestPack and the EIA were equally sensitive. Based on these findings, we suggest the inclusion of these assays in the supplemental testing for detection of antibodies to HIV. Keywords: HIV; Antibody; Rapid assays; Sensitivity; Seroconversion
I. Introduction
Most combined HIV-1/HIV-2 E I A assays now have very high sensitivity and specificity (WHO, * Corresponding author: Tel.: + 47 22 042200; fax: + 47 22 042447.
1994). The progress in the development of rapid instrument-free assays for the detection of antibodies to H I V has produced assays comparable to third-generation EIAs in sensitivity and specificity (Malone et al., 1993; Myrmel et al., 1990; Constantine et al., 1994). Rapid assays have mainly been intended for testing limited numbers of
0928-0197/96/$15.00 © 1996 Elsevier Science B.V. All rights reserved PII S0928-0197(96)00244-9
56
H.H. Samdal et al. / Clinical and Diagnostic' Virology 7 (1996) 55-61
blood donations in emergency situations and in laboratories with minimal laboratory equipment. With the high sensitivity and specificity achieved, the use of these tests might be of value also in the investigation of suspected early HIV infection. This study was therefore designed to assess the sensitivity of four combined HIV-1/HIV-2 instrument-free assays for the detection of antibodies to HIV-1 during seroconversion. Differences between the sensitivities of the rapid assays were revealed by the results obtained in the early phase of seroconversion.
2. Materials and methods
2. I. Serum samples Thirty-eight serum samples were obtained from 14 individuals belonging to groups at risk of acquiring HIV infection. From each subject, at least two samples had been collected (Table 2). All sera had been tested with Abbott second- and third-generation EIA (Abbott GmbH, Diagnostika, Wiesbaden Delkenheim, Germany) and with HIV western blot (HIV blot 2.2, Diagnostic Biotechnology (Pte), Singapore) (Skaug et al., 1994). Only the last sample from each seroconverter was western-blot-positive according to the American Red Cross criteria. HIV EIA-negative samples had been examined with Abbott HIVAG-1 EIA (Abbott Laboratories Diagnostics Division, Chicago, Illinois), and an 'in house' nested PCR (Chomczynski and Sacchi, 1987; Laure et al., 1988). According to the previous testing, 10 sera were listed as probably prior to seroconversion, six as early acute phase and 22 as late seroconversion sera (Table 3). The first 10 sera were negative in all previously performed tests and there were no reports of clinical symptoms at the time of collection. The six early phase sera were negative in the second-generation EIA, but positive in either the third-generation EIA and/or HIV-Ag/PCR. When these six serum specimens were collected, the patients had symptoms of primary HIV infection such as fever, sore throat and generalized lymphadenopathy (Gaines et al., 1988). The 22
late seroconversion specimens were positive in both the second- and the third-generation EIA. All serum samples have been stored at -20°C. Due to lack of material, some specimens were not analyzed with all tests. 2.2. Methods Four assays were evaluated: SUDS®HIV 1 + 2 (Murex Diagnostics, Kent, England), TestPack® HIV-I/HIV-2 (Abbott Laboratories Diagnostics Division, Chicago, Illinois), HIV-SPOT (Diagnostic Biotechnology, Singapore) and CAPILLUS® HIV-1/HIV-2 (Cambridge Biotech, Galway, Ireland). Characteristics of the assays are shown in Table 1. The highest dilution of an 'in house' HIV-antibody positive control specimen was incorporated in each run for each assay. The highest dilution giving a positive result with this specimen for SUDS, TestPack, HIV-SPOT and CAPILLUS was 1/25, 1/50, 1/25 and 1/5 respectively. To accept the test run, the HIV control had to be interpreted as positive. 2.3. Interpretation of test results The tests were read randomly by three technicians, according to the manufacturers' instructions. The criteria for assessing a serum as positive required positive interpretations from all three technicians. For the subjects who contributed to the material, the predictive value of a positive test result was high and indicative of HIV infection. Sera which were interpreted as negative by at least one reader were rated negative.
3. Results
The results of each rapid assay performed on the seroconverter panel are shown in Table 2 together with results of previous testing and information recognized at the date of collection. Of the 38 sera examined, 32 specimens were reactive in one or more of the tests performed, including HIV-Ag and PCR. The other six sera were negative in all tests.
H.H. Samdal et al. / Clinical and Diagnostic Virology 7 (1996) 55-61
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H.H. Samdal et al. / Clinical and Diagnostic Virology 7 (1996) 55 61
58
Table 2 Comparison of results of EIA and rapid tests for the detection of HIV-I antibodies, HIV antigen and HIV-PCR performed on seroconverter sera Sample no.
1.1 1.28 2.1 2.2 b 3.1 3.2 3.38 4,1 4.2 4.3 4.48 5.1 5.2 b 6.1 6.28 7.1 7.2 7.3 b 8.1 8.2 8.3 b 9.1 9.2 b 10.1 10.2 10.3 b 11.1 11.2 b 12.1 12.2 b 13.1 13.2 13.3 13.4 13.58 14.1 14.2 14.3 b
Date
27/08/90 29/01/91 06/06/90 06/06/91 01/10/90 25/02/91 17/04/91 21/03/90 28/03/90 24/04/91 31/07/91 17/10/90 22/07/91 06/11/91 13/11/91 26/08/91 02/09/91 20/11/91 09/03/88 23/08/91 20/11/91 03/07/91 12/12/91 02/05/88 21/10/91 20/02/92 20/11/91 25/03/92 12/03/91 12/08/92 15/01/93 29/09/93 07/10/93 13/10/93 27/10/93 07/12/93 17/12/93 27/12/93
SUDS
P ND N P P P P P P P P P P ND P N N ND N P P N P N P P N P ND P N P P P P P P P
TestPack
N P N P P P P N P P P N P N P N P ND N P P P P N P P N P N P N P P P P N P P
HIV-SPOT
N ND N P N P P N N ND P N P ND N N N ND N N P N P N P P N P ND P N ND P P P ND P P
CAP1LLUS
N ND N P N P P N P P P N P ND P N N ND N N P N P N P P N P ND P N P P P P N P P
Abbott HIV EIA
HIV
Clinical information
2nd gen?~
3rd gen."
AG ~'
PCR
0,1 6.3 0.2 3,3 0.3 9.9 7.2 0.1 1.3 10.9 10,1 0.2 1.6 0.3 5.7 0.1 0,0 8.8 0.3 0,2 7.7 0,2 11,1 0.5 4.1 7.4 1).2 8.0 0.2 6.7 0.3 ND 5.1 6.9 ND 0.97 >8.3 ND
0.2 12.9 0.2 9,5 0.4 10.9 8.7 2.2 14.2 13.2 12.7 0,3 5.9 2.4 7,2 0.2 0.2 15.1 0.2 0.2 12.3 0.2 16.8 0.2 13.7 14.2 0.3 11.8 0.2 13.7 0.1 2.5 3.7 4.1 5.7 3.8 5.1 6.2
0.3 0.4 0.3 1.5 15.1 0.5 0.8 21.4 10.8 0.4 0.3 0.3 0.4 16.8 13.6 0.3 0.2 13.1 0.3 1.7 0.3 0.3 0.3 0.4 0.4 ND 1.3 ND 0,4 ND N N N N N N N N
N ND N P P ND ND ND ND ND ND N P ND ND ND N ND N P ND N ND N ND ND P ND N ND ND ND ND ND ND ND ND ND
Screening Risk group Risk group Risk group Symptoms -~ Symptoms
Risk group Screening Symptoms Screening Screening Risk group Screening Symptoms Screening IVDU IVDU Screening Symptoms Screening Symptoms -Screening Screening Screening Screening --
Symptoms ---
P = positive; N = Negative; ND = not tested; Abbott HIV EIA 2nd gen. = Abbott Recombinant HIV-I/HIV-2 EIA 2.gen.; Abbott H1V EIA 3rd gen = Abbott Recombinant HIV-1/HIV-2 EIA 3.gen.; HIV-AG = Abbott HIVAG-I (antigen assay); HIV-PCR = 'In house' PCR assay; IVDU = Intravenous drug user Relative absorbance value (OD sample/OD cut off). Relative absorbance value>~ 1 = positive result. b Western blot positive.
H.H. Saradal et al. / Clinical and Diagnostic Virology 7 (1996) 55-61
The reactivity of the serum specimens in all anti-HIV assays done is shown in Table 3. Among the 10 sera which were negative in previous testing, the SUDS and TestPack assay had two reactive samples each (No. 1.1, 5.1, 7.2 and 9.1). Among the six sera that were Abbott second-generation negative but positive in one or more of the other tests performed previously, the SUDS assay had four and TestPack two positive samples (No. 3.1, 4.1, 8.2 and 14.1). None of the first 16 samples were HIV-SPOT and CAPILLUS reactive. Of the remaining 22 sera which were Abbott second- and third-generation EIA positive, all but two (No. 4.2 and 6.2) reacted positive in all tests performed.
4. Discussion and conclusion
In developing countries reliable rapid tests may be useful in various testing situations, providing alternatives to conventional testing strategies (Behets et al., 1992; Kline et al., 1994; Sato et al., 1994). In countries with low prevalence of HIV infection, one of the major tasks of the laboratory is to clarify whether positive primary EIA results are due to early seroconversion or unspecific reactions. According to the recommendations from WHO, rapid assays may be included in the testing strategies to detect antibodies against HIV-1/HIV-2 (WHO, 1994). The ability to discover early seroconversion is of major interest in the evaluation of assays detecting antibodies to HIV and our evaluation has focused on the sensitivity of rapid HIV-1/ HIV-2 antibody assays during HIV-1 seroconversion. Based on previous testing, the seroconverter specimens were categorized in three different groups. On the 10 sera which had been categorized as sera collected prior to seroconversion, four specimens (No. 1.1, 5.1, 7.2 and 9.1) reacted only in SUDS and/or TestPack. No information about symptoms of primary HIV infection were linked to these sera and the next samples from the subjects were collected 2.5-9 months later. The reactivity of the rapid tests may indicate that the sera were collected in the early phase of seroconversion, but as there was
59
no information about symptoms of HIV infection, the specificity of these reactions may be questioned. On the six early seroconversion samples, SUDS rates higher than TestPack in detecting HIV-1/HIV-2 antibodies, while HIV-SPOT and CAPILLUS rates lower. This can partly be explained by the fact that SUDS is the only one of these rapid assays designed to detect both IgM and IgG antibodies. In addition, the SUDS procedure includes liquid phase antibody capture before microfiltration, which may expand the sensitivity of the reactions between antibodies and antigens. Since anti-IgG is used as conjugate in TestPack, IgM antibodies are not detected. Nevertheless the sensitivity of this rapid test is above that of the second-generation EIA, approaching the same level as the third-generation EIA in this study. This has also been shown by others (Wauters et al., 1993). On two occasions (No. 3.1, 8.2), SUDS and TestPack were positive while the third-generation EIA was negative. At the time of sample collection, these individuals had symptoms of primary HIV infection and tested positive in HIV-Ag and PCR, which confirms the high sensitivity of the rapid tests. Similar results for SUDS were obtained by Brun-V6zinet et al. (1995) on a panel of early seroconversion samples. In this study, HIV-SPOT and CAPILLUS do not detect antibodies at the same early stages as SUDS and TestPack. The capture antigens in SUDS and TestPack are derived from both g a g and e n v regions of HIV, while the antigens in HIV-SPOT and CAPILLUS are derived from env regions of HIV. At the time of seroconversion, antibodies against the different HIV proteins may be present at different levels, and this might further explain the variation in the sensitivities among the tests. Our study revealed differences in the sensitivity of the rapid assays in the early phase of seroconversion. The most sensitive assays, SUDS and TestPack, were even more sensitive than the third-generation EIA. We therefore suggest including SUDS or TestPack as supplemental tests in the strategy to detect antibodies to HIV.
60
H.H. Samdal et al. / Clinical and Diagnostic Virology 7 (1996) 55-61
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H.H. Samdal et al. / Clinical and Diagnostic Virology 7 (1996) 55-61
References Behets, F., Bishagara, K., Disasi, A., Likin, S., Ryder, R.W., Brown, C. and Quinn, T.C. (1992) Diagnosis of HIV infection with instrument-free assays as an alternative to the ELISA and western blot testing strategy: an evaluation in Central Africa. J. Aquir. Immune Defic. Syndr. 5, 878-882. Brun-Vtzinet, F., Denis, F., Ly, T.-D., Mouillot, L., Rouzioux, C. and Tamalet, C. (1995) R66valuation de la sensibilit6 de 8 trousses unitaires rapides de dtpistage des anticorps anti-VIH. Rev. Fr. Lab. 279, 106-108. Chomczynski, P. and Sacchi, N. (1987) Single-step method of RNA isolation by acid guanidinium thiocyanate-phenolchloroform extraction. Anal. Biochem. 162, 156-159. Constantine, N.T., van der Groen, G., Belsey, E.M. and Tamashiro, H. (1994) Sensitivity of HIV-antibody assays determined by seroconversion panels. AIDS 8, 1715-1720. Gaines, H., yon Sydow, M., Pehrson, P.O. and Lundbergh, P. (1988) Clinical picture of primary HIV infection presenting as a glandular-fever-like illness. Br. Med. J. 297, 13631368. Kline, R.L., Dada, A., Blattner, W. and Quinn, T.C. (1994) Diagnosis and differentiation of HIV-1 and HIV-2 infection by two rapid assays in Nigeria. J. Aquir. Immune Defic. Syndr. 7, 623-626. Laure, F., Courgnand, V., Rouzioux, C., Blanche, S., Veber,
61
F., Burgard, M., Jacomet, C., Griscelli, C. and Brechot, C. (1988) Detection of HIV-1 DNA in infants and children by means of the polymerase chain reaction. Lancet 2, 538541. Malone, J.D., Smith, E.S., Sheffield, J., Bigelow, D., Hyams, K.C., Beardsley, S.G., Lewis R.S. and Roberts C.R. (1993) Comparative evaluation of six rapid serological tests for HIV-1 antibody. J. Aquir. Immune Defic. Syndr. 6, 115119. Myrmel, H., Holm-Hansen, C. and Haukenes, G. (1990) Evaluation of two rapid tests for the detection of HIV-I/HIV-2 antibodies. AIDS 4, 1164-1165. Sato, P.A., Maskill, W.J., Tamashiro, H. and Heymann, D.L. (1994) Strategies for laboratory HIV testing: an examination of alternative approaches not requiring western blot. Bull. WHO 72, 129-134. Skaug, K., Jonassen, T.O. and Figenschau, K.J. (1994) Estimate of the time between HIV infection and diagnosis based on serological parameters. Tidsskr. Nor. Laegeforen. 114, 2099-2101. Wauters, D., Manouvriez, P., Ernst, B. and Hoch, V. (1993) TestPack T M HIV-1/HIV-2, a ten-minute HIV antibody test, compared to second and third generation HIV EIAs. Klin. Lab. 39, 217-218. WHO (1994) Operational characteristics of commercially available assays to detect antibodies to HIV-1 and/or HIV-2 in human sera. Global Programme on AIDS, GPA/ RID/CRD/94,4. World Health Organization, Geneva.
Clinical and Diagnostic Virology 7 (1996) 55-61
Clinical and Diagnostic Virology
Comparison of the sensitivity of four rapid assays for the detection of antibodies to HIV-1/HIV-2 during seroconversion Helvi H. Samdal a,*, Bjorg-Guri Gutigard a, Dolores Labay a, Sissel I. Wiik a, Kjell Skaug a, Anne G. Skar b ~Department of Virology, National Institute of Public Health, Postboks 4404 Torshov, N.0403 Oslo, Norway bDepartment of Microbiology, Ullev~l University Hospital, N-0407 Oslo, Norway
Abstract
Objectives: To compare the sensitivity of four rapid assays for the detection of antibodies against HIV-1 during early seroconversion. Methods: Four rapid assays for the detection of antibodies to HIV-1/HIV-2 (SUDS ® HIV 1 + 2, TestPack ® HIV-1/HIV-2, HIV-SPOT and CAPILLUS ® HIV-1/HIV-2) were evaluated on 38 sera derived from 14 HIV-1 seroconverters, formerly tested with Abbott second- and third-generation HIV-1/HIV-2 enzyme immunoassay (EIA) and Diagnostic Biotechnology HIV blot 2.2. EIA-negative sera had also been investigated by HIV-1 antigen testing and polymerase chain reaction (PCR) analysis detecting HIV-1 proviral DNA. Results: On 16 sera which were Abbott second-generation EIA negative, the SUDS assay rated highest with six positive results. Four sera were TestPack positive. No specimens in this group were HIV-SPOT positive or CAPILLUS positive. Of the remaining 22 sera (Abbott second- and third-generation EIA positive), all but two were positive in all tests. Conclusions: The study revealed differences in the sensitivities of the rapid assays in the early phase of seroconversion. The most sensitive assay, SUDS, was even more sensitive than the Abbott third-generation EIA, while TestPack and the EIA were equally sensitive. Based on these findings, we suggest the inclusion of these assays in the supplemental testing for detection of antibodies to HIV. Keywords: HIV; Antibody; Rapid assays; Sensitivity; Seroconversion
I. Introduction
Most combined HIV-1/HIV-2 E I A assays now have very high sensitivity and specificity (WHO, * Corresponding author: Tel.: + 47 22 042200; fax: + 47 22 042447.
1994). The progress in the development of rapid instrument-free assays for the detection of antibodies to H I V has produced assays comparable to third-generation EIAs in sensitivity and specificity (Malone et al., 1993; Myrmel et al., 1990; Constantine et al., 1994). Rapid assays have mainly been intended for testing limited numbers of
0928-0197/96/$15.00 © 1996 Elsevier Science B.V. All rights reserved PII S0928-0197(96)00244-9
56
H.H. Samdal et al. / Clinical and Diagnostic' Virology 7 (1996) 55-61
blood donations in emergency situations and in laboratories with minimal laboratory equipment. With the high sensitivity and specificity achieved, the use of these tests might be of value also in the investigation of suspected early HIV infection. This study was therefore designed to assess the sensitivity of four combined HIV-1/HIV-2 instrument-free assays for the detection of antibodies to HIV-1 during seroconversion. Differences between the sensitivities of the rapid assays were revealed by the results obtained in the early phase of seroconversion.
2. Materials and methods
2. I. Serum samples Thirty-eight serum samples were obtained from 14 individuals belonging to groups at risk of acquiring HIV infection. From each subject, at least two samples had been collected (Table 2). All sera had been tested with Abbott second- and third-generation EIA (Abbott GmbH, Diagnostika, Wiesbaden Delkenheim, Germany) and with HIV western blot (HIV blot 2.2, Diagnostic Biotechnology (Pte), Singapore) (Skaug et al., 1994). Only the last sample from each seroconverter was western-blot-positive according to the American Red Cross criteria. HIV EIA-negative samples had been examined with Abbott HIVAG-1 EIA (Abbott Laboratories Diagnostics Division, Chicago, Illinois), and an 'in house' nested PCR (Chomczynski and Sacchi, 1987; Laure et al., 1988). According to the previous testing, 10 sera were listed as probably prior to seroconversion, six as early acute phase and 22 as late seroconversion sera (Table 3). The first 10 sera were negative in all previously performed tests and there were no reports of clinical symptoms at the time of collection. The six early phase sera were negative in the second-generation EIA, but positive in either the third-generation EIA and/or HIV-Ag/PCR. When these six serum specimens were collected, the patients had symptoms of primary HIV infection such as fever, sore throat and generalized lymphadenopathy (Gaines et al., 1988). The 22
late seroconversion specimens were positive in both the second- and the third-generation EIA. All serum samples have been stored at -20°C. Due to lack of material, some specimens were not analyzed with all tests. 2.2. Methods Four assays were evaluated: SUDS®HIV 1 + 2 (Murex Diagnostics, Kent, England), TestPack® HIV-I/HIV-2 (Abbott Laboratories Diagnostics Division, Chicago, Illinois), HIV-SPOT (Diagnostic Biotechnology, Singapore) and CAPILLUS® HIV-1/HIV-2 (Cambridge Biotech, Galway, Ireland). Characteristics of the assays are shown in Table 1. The highest dilution of an 'in house' HIV-antibody positive control specimen was incorporated in each run for each assay. The highest dilution giving a positive result with this specimen for SUDS, TestPack, HIV-SPOT and CAPILLUS was 1/25, 1/50, 1/25 and 1/5 respectively. To accept the test run, the HIV control had to be interpreted as positive. 2.3. Interpretation of test results The tests were read randomly by three technicians, according to the manufacturers' instructions. The criteria for assessing a serum as positive required positive interpretations from all three technicians. For the subjects who contributed to the material, the predictive value of a positive test result was high and indicative of HIV infection. Sera which were interpreted as negative by at least one reader were rated negative.
3. Results
The results of each rapid assay performed on the seroconverter panel are shown in Table 2 together with results of previous testing and information recognized at the date of collection. Of the 38 sera examined, 32 specimens were reactive in one or more of the tests performed, including HIV-Ag and PCR. The other six sera were negative in all tests.
H.H. Samdal et al. / Clinical and Diagnostic Virology 7 (1996) 55-61
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H.H. Samdal et al. / Clinical and Diagnostic Virology 7 (1996) 55 61
58
Table 2 Comparison of results of EIA and rapid tests for the detection of HIV-I antibodies, HIV antigen and HIV-PCR performed on seroconverter sera Sample no.
1.1 1.28 2.1 2.2 b 3.1 3.2 3.38 4,1 4.2 4.3 4.48 5.1 5.2 b 6.1 6.28 7.1 7.2 7.3 b 8.1 8.2 8.3 b 9.1 9.2 b 10.1 10.2 10.3 b 11.1 11.2 b 12.1 12.2 b 13.1 13.2 13.3 13.4 13.58 14.1 14.2 14.3 b
Date
27/08/90 29/01/91 06/06/90 06/06/91 01/10/90 25/02/91 17/04/91 21/03/90 28/03/90 24/04/91 31/07/91 17/10/90 22/07/91 06/11/91 13/11/91 26/08/91 02/09/91 20/11/91 09/03/88 23/08/91 20/11/91 03/07/91 12/12/91 02/05/88 21/10/91 20/02/92 20/11/91 25/03/92 12/03/91 12/08/92 15/01/93 29/09/93 07/10/93 13/10/93 27/10/93 07/12/93 17/12/93 27/12/93
SUDS
P ND N P P P P P P P P P P ND P N N ND N P P N P N P P N P ND P N P P P P P P P
TestPack
N P N P P P P N P P P N P N P N P ND N P P P P N P P N P N P N P P P P N P P
HIV-SPOT
N ND N P N P P N N ND P N P ND N N N ND N N P N P N P P N P ND P N ND P P P ND P P
CAP1LLUS
N ND N P N P P N P P P N P ND P N N ND N N P N P N P P N P ND P N P P P P N P P
Abbott HIV EIA
HIV
Clinical information
2nd gen?~
3rd gen."
AG ~'
PCR
0,1 6.3 0.2 3,3 0.3 9.9 7.2 0.1 1.3 10.9 10,1 0.2 1.6 0.3 5.7 0.1 0,0 8.8 0.3 0,2 7.7 0,2 11,1 0.5 4.1 7.4 1).2 8.0 0.2 6.7 0.3 ND 5.1 6.9 ND 0.97 >8.3 ND
0.2 12.9 0.2 9,5 0.4 10.9 8.7 2.2 14.2 13.2 12.7 0,3 5.9 2.4 7,2 0.2 0.2 15.1 0.2 0.2 12.3 0.2 16.8 0.2 13.7 14.2 0.3 11.8 0.2 13.7 0.1 2.5 3.7 4.1 5.7 3.8 5.1 6.2
0.3 0.4 0.3 1.5 15.1 0.5 0.8 21.4 10.8 0.4 0.3 0.3 0.4 16.8 13.6 0.3 0.2 13.1 0.3 1.7 0.3 0.3 0.3 0.4 0.4 ND 1.3 ND 0,4 ND N N N N N N N N
N ND N P P ND ND ND ND ND ND N P ND ND ND N ND N P ND N ND N ND ND P ND N ND ND ND ND ND ND ND ND ND
Screening Risk group Risk group Risk group Symptoms -~ Symptoms
Risk group Screening Symptoms Screening Screening Risk group Screening Symptoms Screening IVDU IVDU Screening Symptoms Screening Symptoms -Screening Screening Screening Screening --
Symptoms ---
P = positive; N = Negative; ND = not tested; Abbott HIV EIA 2nd gen. = Abbott Recombinant HIV-I/HIV-2 EIA 2.gen.; Abbott H1V EIA 3rd gen = Abbott Recombinant HIV-1/HIV-2 EIA 3.gen.; HIV-AG = Abbott HIVAG-I (antigen assay); HIV-PCR = 'In house' PCR assay; IVDU = Intravenous drug user Relative absorbance value (OD sample/OD cut off). Relative absorbance value>~ 1 = positive result. b Western blot positive.
H.H. Saradal et al. / Clinical and Diagnostic Virology 7 (1996) 55-61
The reactivity of the serum specimens in all anti-HIV assays done is shown in Table 3. Among the 10 sera which were negative in previous testing, the SUDS and TestPack assay had two reactive samples each (No. 1.1, 5.1, 7.2 and 9.1). Among the six sera that were Abbott second-generation negative but positive in one or more of the other tests performed previously, the SUDS assay had four and TestPack two positive samples (No. 3.1, 4.1, 8.2 and 14.1). None of the first 16 samples were HIV-SPOT and CAPILLUS reactive. Of the remaining 22 sera which were Abbott second- and third-generation EIA positive, all but two (No. 4.2 and 6.2) reacted positive in all tests performed.
4. Discussion and conclusion
In developing countries reliable rapid tests may be useful in various testing situations, providing alternatives to conventional testing strategies (Behets et al., 1992; Kline et al., 1994; Sato et al., 1994). In countries with low prevalence of HIV infection, one of the major tasks of the laboratory is to clarify whether positive primary EIA results are due to early seroconversion or unspecific reactions. According to the recommendations from WHO, rapid assays may be included in the testing strategies to detect antibodies against HIV-1/HIV-2 (WHO, 1994). The ability to discover early seroconversion is of major interest in the evaluation of assays detecting antibodies to HIV and our evaluation has focused on the sensitivity of rapid HIV-1/ HIV-2 antibody assays during HIV-1 seroconversion. Based on previous testing, the seroconverter specimens were categorized in three different groups. On the 10 sera which had been categorized as sera collected prior to seroconversion, four specimens (No. 1.1, 5.1, 7.2 and 9.1) reacted only in SUDS and/or TestPack. No information about symptoms of primary HIV infection were linked to these sera and the next samples from the subjects were collected 2.5-9 months later. The reactivity of the rapid tests may indicate that the sera were collected in the early phase of seroconversion, but as there was
59
no information about symptoms of HIV infection, the specificity of these reactions may be questioned. On the six early seroconversion samples, SUDS rates higher than TestPack in detecting HIV-1/HIV-2 antibodies, while HIV-SPOT and CAPILLUS rates lower. This can partly be explained by the fact that SUDS is the only one of these rapid assays designed to detect both IgM and IgG antibodies. In addition, the SUDS procedure includes liquid phase antibody capture before microfiltration, which may expand the sensitivity of the reactions between antibodies and antigens. Since anti-IgG is used as conjugate in TestPack, IgM antibodies are not detected. Nevertheless the sensitivity of this rapid test is above that of the second-generation EIA, approaching the same level as the third-generation EIA in this study. This has also been shown by others (Wauters et al., 1993). On two occasions (No. 3.1, 8.2), SUDS and TestPack were positive while the third-generation EIA was negative. At the time of sample collection, these individuals had symptoms of primary HIV infection and tested positive in HIV-Ag and PCR, which confirms the high sensitivity of the rapid tests. Similar results for SUDS were obtained by Brun-V6zinet et al. (1995) on a panel of early seroconversion samples. In this study, HIV-SPOT and CAPILLUS do not detect antibodies at the same early stages as SUDS and TestPack. The capture antigens in SUDS and TestPack are derived from both g a g and e n v regions of HIV, while the antigens in HIV-SPOT and CAPILLUS are derived from env regions of HIV. At the time of seroconversion, antibodies against the different HIV proteins may be present at different levels, and this might further explain the variation in the sensitivities among the tests. Our study revealed differences in the sensitivity of the rapid assays in the early phase of seroconversion. The most sensitive assays, SUDS and TestPack, were even more sensitive than the third-generation EIA. We therefore suggest including SUDS or TestPack as supplemental tests in the strategy to detect antibodies to HIV.
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