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NLM AIDSLINE
Prospective follow-up study of individuals with antibody patterns suggestive of early HIV infection.
Schupbach J; Tomasik Z; Jendis J; Boni J; Swiss National Center for
December 30, 1992
Int Conf AIDS. 1992 Jul 19-24;8(3):36 (abstract no. PuA 6153). Unique

OBJECTIVE: Follow-up of individuals initially presenting with border-line or low-positive screening results and a Western blot result at least positive according to CDC/WHO interpretation, but FDA-indeterminate. METHODS: All individuals with such results were enrolled into a follow-up study and tested by WB (serum dilution 1/25), serum Ag, virus culture (VC) and PCR, using primers/probes from gag, env, and LTR. The analytical sensitivity of the PCR procedure was shown to be 1 copy/microgram DNA. The specificity of a positive PCR reaction was 99.25% (4 false-positive out of 531 negative control reactions) and that of a positive PCR result 100% (187 materials tested). WB results were evaluated according to CDC, CRSS, ARC, and FDA interpretation rules. RESULTS: On follow-up, in 19 (56%) of 34 cases enrolled in 1991 anti-env antibodies were no longer present. In these, contamination of the first sample could not be ruled out as a cause for the initial positivity. Of the remaining 15, only 6 (40%) were shown to be infected by PCR and, in 5, by full seroconversion; 2 were VC+ and 1 indeterminate, but all were Ag-neg. Of the remaining 9 (60%), 7 were still WB-pos by at least CDC interpretation, but did not fully seroconvert. Two more were CDC-indeterminate, but still had anti-env antibodies. All 9 were negative by Ag, VC and PCR, except 1 case who was PCR indeterminate in 1 of 2 follow-up samples. Long-term observation of 18 different such individuals detected earlier showed the continued presence of such antibody patterns in otherwise healthy individuals for up to 5 years. PCR results were never clear-positive, but showed an indeterminate result in 4/18 cases. Antibody patterns and concentrations varied over time, some individuals became again screening-negative. CONCLUSION: The results show that less than half of the individuals presenting with serological results suggestive of early HIV infection rapidly progress to a state where HIV infection can be demonstrated beyond doubt. At least as many of these individuals remain, sometimes for years, in a state of diagnostic twilight, where both serological and PCR results are borderline. Strict adherence to the WB interpretation rules suggested by CDC or WHO may lead to confirmed false-positive results. If, on the other hand, these individuals are truly infected, they represent a stable state of low-level infection that is different from that of fully seroconverting individuals. The most sensitive diagnostic tests are not sensitive enough to resolve this problem.

Antibodies/*BLOOD Blotting, Western False Positive Reactions Follow-Up Studies Gene Products, env/IMMUNOLOGY Genes, env Genes, gag Human HIV/GENETICS/*ISOLATION & PURIF HIV Antibodies/*BLOOD HIV Infections/DIAGNOSIS/*IMMUNOLOGY/PHYSIOPATHOLOGY *HIV Seropositivity Polymerase Chain Reaction Prospective Studies Time Factors ABSTRACT

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