- A negative test is a definitive negative unless tested in the "window period" (first 3 months post-exposure).
- Positive tests are considered preliminary positive results and should be confirmed with a Western blot or IFA. Note that confirmation tests done only with EIA have yielded false negative results (MMWR 2004;53:221).
- Indeterminate tests should be repeated in 1 month.
- Resource-limited countries confirm positive tests with a second rapid test from a different supplier. This permits same visit definitive results with positive tests as well as negative results.
- UniGold detects lgM as well as lgG and consequently may give more positive tests in early stage disease.
Sensitivity and specificity of these rapid tests are consistently >99%(JAIDS 1993;6:115; Am J Emerg Med 1991;9:416; Am Intern Med 1996;125:471; J Human Virol 2001;4:278; Internat J STD AIDS 2002;13: 171; J Clin Microbiol 2003;41:3868; J Lab Med 2003;27:288), but the positive predictive value is dependent on HIV prevalence, an observation that emphasizes the need for a confirmatory test as shown in Table 2-3.
INDICATIONS: Rapid tests are recommended for general use and may be especially useful where rapid results are important, as with occupational exposure (MMWR 2001;50[RR-11]:1; Infect Control Hosp Epidemiol 2001;22:289), in pregnant women who present in labor without prior testing (JAMA 2004;292:219), in outreach settings (MMWR 2006;55:673), and in
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TABLE 2-3:
