0521779407-09 CUNY1086/Karliner 0 521 77940 7 June 4, 2007 21:13
Human Immunodeficiency Virus Type 1 (HIV-1) 731➣Home Test Kits require blood on a filter strip that is then tested
by EIA and WB; 100% sensitive, 99.95% specific
➣Rapid Detection Kits (< 30 minutes) requires confirmation by
standard serology due to decreased specificity (98.9%–100%)
■Other secretions
➣Oral secretion kit detects Abs in oral secretions and requires WB
confirmation on oral secretions; 99.9% sensitive and specific
➣Urine kits detect Abs in urine and require urine WB confirmation;
99.7% sensitive, 100% specific
Other Tests
■HIV-1 p24 Antigen (Ag) used to screen all donated blood; can be
used to diagnose acute HIV syndrome though becomes negative
with appearance of high levels of anti-p24 Abs thus nucleic acid-
based diagnosis preferred in such cases
■Qualitative PCR on circulating cells/plasma can be used in early dis-
ease e.g. acute HIV infection, newborns; also used to resolve inde-
terminate Western blots; detects >99% HIV-1 variants from US and
Europe (subtype B); limited use as expensive and not generally avail-
able
■Quantitative measurement of HIV nucleic acid sequences in plasma
(‘viral loads (VL)/viral burdens) most widely used test to diagnose
acute HIV infection, initiate antiretroviral Rx, predict disease prog-
nosis, monitor response to treatment, predict likelihood of perinatal
transmission from HIV+mother to infant
■At least 3 competing methods exist:
■1. DNA PCR Amplification with Reverse transcriptase (RT-PCR)
■2. Nucleic acid sequence-based amplification (NASBA)
■3. Signal amplification by DNA branched-chain technique (bDNA)
■For a given assay, need a change of > 0.5 log to be a significant change
■Tests for HIV-1 Antiretroviral Drug Resistance used to aid Rx changes
and initiation of Rx during acute infection, pregnancy, etc.
■Two types of in vitro resistance tests:
■1. genotypic resistance-detects gene mutation, use to predict phe-
notypic resistance.
■2. Phenotypic resistance-assess ability of HIV to grow in vitro in pres-
ence of HIV antiretroviral drugs.
Imaging
■None needed unless evidence of possible acute opportunistic
infection; CXR for those who are PPD+; CXR for TB screening advo-
cated by some irregardless of PPD result