it about window period of HIV

1. Window period of acute infection
The window period represents the period between the time of initial infection with HIV
and the time when HIV antibodies can be detected in the blood stream. During this
period, HIV replicates in the blood and lymph nodes; patients are highly infectious and
may be symptomatic, but their blood will test negative for HIV antibody. The window
period can last up to 12 weeks and may vary between assays using different
methodologies.
 HIV infection cannot be successfully diagnosed during the window period using
antibody-based assays. Assays which detect part of the virion (as opposed to
the antibody of the infected host) are employed in this situation.
 The tests most commonly used in this situation are the p24 antigen and the
proviral HIV DNA assays.
 The p24 antigen assay detects the viral protein p24. The assay has high
specificity (>95%) but its sensitivity is low (80%).
 The proviral DNA detects the presence of HIV DNA that is integrated into the
host genes in peripheral blood lymphocytes.
 This assay is based on polymerase chain reaction (PCR) technology and is
highly specific as well as highly sensitive (98% and >99%, respectively).
 The performance of this test in detection of HIV-1 and non-HIV-1 subtypes has
not been determined. The HIV DNA assay is available only in the research
setting.
 HIV RNA PCR tests are not recommended for the diagnosis of acute HIV
infection because of the significant rates of false-positive results (10%).
Typically, true positive results are greater than 100,000 copies/ml whereas
false-positive results are generally less than 1000 copies/ml.
20-05-2015