![]() The observed sequence of development of HIV antibodies is dependent upon the inherent technical sensitivities of the assays employed as well as the biology of infection. Incorrect classification by WB can occur ( 107). Thus, in some early epidemiologic studies some persons may have been misclassified. Whereas the initial CDC WB interpretative criteria accepted p24 alone as sufficient for WB confirmation of sera that were repeatedly reactive by EIA, retrovirologists now routinely treat such WB patterns as equivocal. This persistent reactivity pattern can be associated with a relatively sharp (i.e. However, persons with solitary p24 bands may be found among historic blood donor sera ( 23) and instances of prolonged persistent p24 reactivity in low risk subjects have been noted. Some data suggested that p24 core antibody frequently preceded envelope antibodies. When single bands were noted as the sole reactivity, in some instances subsequent testing of follow-up sera showed clear-cut broad reactivities-suggesting that the initial result was consistent with early HIV infection ( 106). However, the interpretation of WBs with isolated reactivities was highly controversial ( 105). In the absence of gp41 on WB, there initially was widespread agreement that the combination of p24 and pr53gag (by RIPA) provided reliable confirmation. In some states, only a single centralized lab is permitted to perform testing to help ensure quality control. Such problems led to calls for more formalized and restrictive interpretation of WBs ( Table 8.4). Thus, aberrant findings clearly required follow-up ( 104). Greater experience and the extension of testing to many labs revealed that significant variations in WB reactivity were observed in practice, with results frequently discordant compared to those from reference WB laboratories ( 103). As in other areas of medicine, adequate training in subtle differences can be essential. Since a solitary sharp (thin) WB band at p40 was likely to indicate reactivity unrelated to HIV, an experienced virologist and laboratory were crucial in making this critical but subjective distinction during the first years of HIV testing. ![]() It was also clearly necessary to have further confirmatory evidence for sera from very low risk group sera. In some lots of WB kits, the gp120 and gp160 bands may not be sufficiently separated to appear as clearly independent bands.Ī broad gp41 WB band was initially accepted as adequate confirmation of sera from a person at high risk of HIV. Thus, the WB's that detect gp120 and gp160 are helpful in classifying potentially ambiguous sera. When several related antibodies are detected, the pattern still has high predictive value. When classic patterns are present, positivity is a virtual certainty ( Table 8.4). WB and RIPA are said to confirm a repeatedly reactive EIA screening test result or rapid HIV test result because they can readily reveal the specific anti-HIV antibodies responsible for the reactive result. Cowan, in AIDS and Other Manifestations of HIV Infection (Fourth Edition), 2004 Utilization and Interpretation of WB and RIPA
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