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Soru

Zorluk: KolayInfectious Diseases

A 24-year-old man presents to the clinic for a routine wellness examination and sexual health screening. He reports having multiple male sexual partners and inconsistent condom use. He currently feels well and has no acute symptoms. The physician decides to screen him for human immunodeficiency virus (HIV). Assuming the patient has an acute HIV-1 infection, arrange the following laboratory evaluation steps in the correct chronological sequence according to the standard diagnostic algorithm.

  1. 1Perform a fourth-generation HIV-1/2 antigen/antibody combination immunoassay
  2. 2Perform an HIV-1/HIV-2 antibody differentiation immunoassay
  3. 3Perform an HIV-1 nucleic acid test (NAT)
  4. 4Measure baseline CD4 cell count and HIV RNA viral load

Cevap

The correct chronological sequence is: 1) Fourth-generation combination immunoassay, 2) Antibody differentiation immunoassay, 3) HIV-1 nucleic acid test (NAT), and 4) Baseline CD4 cell count and viral load.
The standard HIV diagnostic algorithm dictates starting with a highly sensitive screening test (4th-generation antigen/antibody immunoassay). If reactive, it is followed by a highly specific confirmatory test (HIV-1/2 antibody differentiation immunoassay). In acute HIV, the screening test is reactive due to the presence of the p24 antigen, but the differentiation assay is negative because antibodies have not yet seroconverted. This discordant result requires an HIV-1 NAT to confirm acute infection. Finally, after confirmation, baseline laboratory values (CD4 count and viral load) are drawn to guide treatment.

Adım Adım Çözüm

1
Identify the recommended initial screening test.
A fourth-generation HIV-1/2 antigen/antibody combination immunoassay is performed.
This is the most sensitive initial test because it detects both the p24 antigen (present early in acute infection) and HIV antibodies.
2
Determine the next step following a reactive screening test.
An HIV-1/HIV-2 antibody differentiation immunoassay is performed.
A reactive initial screen must be confirmed. The differentiation assay distinguishes between HIV-1 and HIV-2 and confirms the presence of antibodies.
3
Resolve the indeterminate or negative confirmatory result seen in acute infection.
An HIV-1 nucleic acid test (NAT) is performed.
Because the patient has an acute infection, antibodies may not yet be present in sufficient quantities, making the differentiation assay negative. The NAT directly detects the viral RNA, confirming acute HIV-1.
4
Plan post-diagnostic management.
CD4 cell count and HIV RNA viral load are measured.
Once the diagnosis is confirmed, baseline immune and viral parameters must be established before or alongside initiating antiretroviral therapy.

Anahtar Kavram

The standard HIV diagnostic algorithm requires sequential testing: initial screening with a 4th-generation antigen/antibody assay, followed by an antibody differentiation assay if positive, and a nucleic acid test (NAT) if the differentiation assay is negative or indeterminate (which is characteristic of acute HIV infection).
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