Annals of Clinical & Laboratory Science 38:293-295 (2008)
© 2008 Association of Clinical Scientists
Negative Results of a Rapid Antibody Test for HIV in a 16-Month-Old Infant with AIDS
Yunzhi Zhang1,
Jiangrong Wang1,
Gregory J. Wilson2,
Yi-Wei Tang3,4 and
Hong-Zhou Lu1
1 Department of Infectious Diseases, Shanghai Public Health Clinical Center, affiliated with Fudan University, Shanghai, China; 2 Departments of Pediatrics, 3 Medicine, and 4 Pathology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
Address correspondence to Yi-Wei Tang, M.D., Ph.D., Molecular Infectious Disease Lab, Vanderbilt University Hospital, 4605 TVC, Nashville, TN 37232, USA; tel 615 322 2035; fax 615 343 8420; e-mail yiwei.tang{at}vanderbilt.edu; or to Hong-Zhou Lu, M.D., Ph.D., Department of Infectious Diseases, Shanghai Public Health Clinical Center, Fudan University, 2901 Cao Lang Road, Shanghai 201508, China; tel/fax 86 21 5724 8758; e-mail luhongzhou{at}fudan.edu.cn.
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Abstract
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In a 16-mo-old infant born to an HIV-infected mother, repeatedly negative results of a HIV rapid antibody test had been reported during the past 6 mo. The infant presented with several HIV-defining illnesses and HIV RT-PCR testing confirmed the presence of HIV infection. There are at least 2 possible explanations for the child’s false-negative rapid HIV test results: First, his primary antibody production may have been suppressed by the presence of maternal IgG antibodies. Second, his mother was highly immunosuppressed, so that the low level of maternally derived IgG was only detected by HIV-EIA and Western blot. Our data suggest that the HIV rapid antibody test may not be sufficiently sensitive to detect HIV antibodies in infants aged <18 mo.
Keywords: infant HIV infection, rapid antibody test for HIV, screening tests for AIDS
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Case Report
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A 16-mo-old boy presented with prolonged fever and oral candidiasis for the past 6 mo. He was a term infant delivered by cesarean section without complication. He was breast-fed for the first 6 days of life and then switched to bottle-feeding. At one mo of age, he developed oral candidiasis and was treated with an oral anti-fungal agent (mycostatin), but he did not respond to treatment. Subsequently, he was hospitalized due to prolonged fever and cough and diagnosed with Pseudomonas aeruginosa infection by sputum culture. His cytomegalovirus and adenovirus IgM antibody tests were positive. Ultrasound examination of the abdomen revealed hepatosplenomegaly.
His mother was human immunodeficiency virus (HIV) antibody-positive one wk before delivery, which was subsequently confirmed by a Genetic System HIV-1 Western-blot (Beckman Coulter, Fullerton, CA). Her CD4+ cell count was 212/mm3 and HIV viral load was 1.6x106 copies/ ml (Versant HIV-1 bDNA 3.0 Assay, Bayer Corp., Berkeley, CA). The boy had a rapid HIV-1/2 antibody test (Determine HIV-1/2 Test, Abbott Laboratories, Abbott Park, IL) [1] performed twice in serum at age 5- and 7-mo, which were negative. The Abbott rapid test was repeated at age 7- and 8-mo during his hospitalization and the results remained negative; however, HIV-1/2 antibody was detected in his serum by an enzyme-linked immunosorbent assay (TNA-Abb, Dainabot Co., Tokyo, Japan) at the time of readmission when he was 7-mo old. HIV-1 Western-blot was performed in plasma at the Shanghai Centers for Disease Control and Prevention, which revealed the presence of a single HIV gp120 band. His HIV viral loads ranged from 1.5 to 2.2x105 copies/ml (Versant HIV-1 bDNA 3.0 Assay) in plasma during his hospitalization. The HIV Western-blot and viral load assays were performed according to the manufacturers’ recommended procedures.
Using 3 frozen serum specimens collected at different time periods during his hospitalization, total RNA was extracted by an RNA Purification Kit (TaKaRa Biomedical Co., Japan). A fragment spanning HIV-1 nucleotide positions from 4,228 to 4,808 was detected by RT-PCR (Primer set: P1: 5' –CTG GCT CCA TTT CTT GCT CT–3' and P2: 5'–TAG TGT CCA TTC ATT GTG TG–3'), and all 3 specimens were positive. The amplified DNA fragments were subcloned into a pET32b(+) plasmid, and nucleotide sequencing showed a full-length vif gene (582 base-pairs). Nucleotide sequences of the 3 amplification products were identical with a similarity of 96.56% to a vif gene previously isolated from an HIV patient in China (accession number AY008716
[GenBank]
) [2].
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Discussion
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This child had prolonged fever and oral candidiasis at 1-mo of age and was suspected to be HIV-infected by ELISA, which was confirmed by HIV-1 RT-PCR. The Western blot only revealed the presence of a single gp120 band, and the HIV rapid assay remained negative. This type of case has been reported previously [3,4], but this is the first report in China. Rapid HIV tests provide results in min, use minimal laboratory equipment, and have been widely used especially in resource-limited settings since their introduction. However, false-negative results have happened, especially when the tests are used in infants [1,4].
Our case further demonstrates that the rapid HIV antibody test can result in false-negative results in infants. There are at least two possible explanations for the child’s negative rapid HIV-1 antibody results. First, his primary antibody production has been suppressed by the presence of maternal IgG antibodies [5]. Second, his mother was highly immunosuppressed; therefore, the low level of maternally-derived circulating HIV-1 IgG was only detected by HIV-EIA and Western blot. While the antigen components used in the rapid assay merit further investigation, our data indicate that the HIV rapid assay test is not reliable in screening for HIV infection in infants aged <18 months.
Due to passive transfer of maternal antibody during pregnancy, infants born to HIV-infected mothers remain antibody-positive into the second year of life, even if they are not infected. For this reason, standard HIV antibody tests cannot reliably confirm HIV infection in infants until after maternal antibodies have disappeared. Tests that can diagnose pediatric HIV infection accurately during the first year of life include HIV-PCR assays, HIV culture, and repeat p24 antigen tests [6,7]. The sensitivity and the specificity of an HIV DNA PCR at birth have been estimated to be 50% and 99%, respectively. The sensitivity of the test improves dramatically in the first weeks of life and reaches a sensitivity of 90% or better when used in infants who are older than 1-mo of age. Two negative tests by PCR or viral culture after 3-mo of age would indicate that a child is not infected and would be more useful than screening serology.
Although HIV DNA PCR and HIV RT-PCR are important tests in this clinical situation, they must be interpreted carefully. Several studies demonstrate a high sensitivity for both tests, however, specificities vary among reports. Also, HIV PCR testing should be repeated at regular, defined intervals, preferably lasting until the HIV antibody status of the infant is resolved [8,9]. HIV RNA amplification assays may be better at detecting HIV-infected infants than DNA PCR. In a cohort study, qualitative nucleic acid sequence-based amplification (NASBA) assay was shown to be highly specific and more sensitive than DNA PCR. NASBA results from infected children were compared with DNA PCR results from the same blood samples taken during the first 3 mo of life from HIV-infected and uninfected children. Sensitivity, specificity, and predictive values were calculated. The conclusion was that qualitative RNA assays (including RT-PCR) may be useful for diagnosing and excluding perinatal HIV infection in children after the first week of life for such purposes as initiating antiretroviral therapy and other treatment, resolving parental uncertainty, determining timing of transmission, and providing endpoints for intervention trials [10].
Infants born to HIV-infected mothers are at great risk of becoming infected with HIV during labor and delivery. HIV is present in breast-milk, and the risk of transmission during breast-feeding depends on several factors including infant age, pattern of breast-feeding, breast-feeding duration, breast health, maternal viral load, and maternal immune status. This child was born by cesarean section without complication; however, he was breast-fed for the first 6 days of life, and his mother did not use optimal antiretroviral therapy during pregnancy, which are both risk-factors for mother-to-child-transmission.
In conclusion, the HIV rapid assay may not be sensitive enough for testing HIV antibodies in infants who are less than 18-mo old. Other sensitive assays, including fourth-generation EIA as well as nucleic acid amplification-based assays, should be used.
Nucleotide sequence accession number.
The nucleotide sequence of the vif gene determined in this study has been submitted to the GenBank sequence databases and assigned the accession number EU011583.
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Acknowledgements
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The authors thank James Chappell and Peter Wright for critically reviewing the manuscript.
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References
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