Indeterminate Human Immunodeficiency Virus Type 1 Western Blots: Seroconversion Risk, Specificity of Supplemental Tests, and an Algorithm for Evaluation

Abstract

The human immunodeficiency virus type 1 (HIV-1) Western blot is indeterminate in 10%-20% of sera reactive by EIA. Eighty-nine individuals with prior repeatedly reactive EIA and indeterminate Western blots were followed prospectively to study the risk of seroconversion and specificity of supplemental tests. Four high-risk cases seroconverted within 10 months after enrollment (seroconversion risk, 4.5%, 95% confidence interval, 1.2%-11.1%). Among cases with p24 bands initially, 4 (18.2%) of 22 high-risk individuals seroconverted compared with 0 of 33 low-risk cases (P = .03). Specificities of HIV-1 culture, serum p24 antigen, polymerase chain reaction, and recombinant ENV 9 EIA were 100%, 100%, 98.6%, and 94.4%, respectively. An expedited evaluation protocol is proposed. Low-risk individuals with nonreactive EIAs upon repeat testing do not need further follow-up; high-risk individuals should be followed serologically for at least 6 months, especially those with p24 bands on Western blot.

Reducción de la transmisión madre hijo del VIH en Colombia: dos años de experiencia nacional, 2003-2005.

“…Aquéllas detectadas como positivas o indeterminadas ingresaron al protocolo de prevención. A las gestantes con resultado indeterminado se les inició manejo farmacológico como conducta profiláctica, ante la posibilidad de que el resultado correspondiera al periodo de ventana inmunológica (34)(35)(36).…”

Diagnosis of Human Immunodeficiency Virus Infection Using an Immunoglobulin E-Based Assay

“…Repeatedly reactive samples were confirmed by Western blot (Biotech Corp., Rockeville, Md.). Western blots were evaluated according to U.S. Department of Defense (DOD) criteria that conform to the Association of State and Territorial Public Health Laboratory Directors Standards (4,8). DOD criteria for a positive Western blot are the presence of at least two of the following three major HIV protein bands: gp41, p24, and gp120-160.…”

“…The indeterminate specimens were considered negative since most low-risk individuals with sera containing only HIV-1 core antigens, other than p24, are rarely infected or have seroconverted (4,8).…”

Point-of-Care Testing for HIV: HIV Counselling and Testing

“…In addition, the HIV vaccine will produce a false positive result (8,9). The window period is one reason for an indeterminate Western blot; the test may be given when antibodies to all of the HIV antigens that characterize the positive test have not yet developed (8,11). However, the reason for many indeterminate Western blots is not known.…”

“…However, the reason for many indeterminate Western blots is not known. Most individuals who remain repeatedly Western blot indeterminate in the absence of recent exposures should be considered HIV neg-ative and counselled as such (9,11). Until that determination is made, however, counselling for an indeterminate Western blot should be the same as that for a newly identified HIV (9).…”