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Zorluk: OrtaOrdering Laboratory Tests

A 28-year-old man comes to the clinic for sexually transmitted infection screening. He reports engaging in unprotected receptive anal intercourse with a new male partner approximately 3 weeks ago. He is currently asymptomatic and his physical examination is unremarkable. The physician suspects a potential acute HIV infection and initiates the diagnostic workup. Arrange the following laboratory steps in the correct chronological sequence for diagnosing and initially evaluating this patient according to standard HIV testing guidelines.

  1. 1Perform a 4th-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 amplification test (NAT)
  4. 4Obtain a baseline CD4+ T-lymphocyte count and antiretroviral genotypic resistance profile

Cevap

The correct diagnostic sequence is: 1) 4th-generation HIV-1/2 antigen/antibody combination immunoassay, 2) HIV-1/HIV-2 antibody differentiation immunoassay, 3) HIV-1 nucleic acid amplification test (NAT), and 4) baseline CD4+ T-lymphocyte count and antiretroviral genotypic resistance profile.
The Centers for Disease Control and Prevention (CDC) recommends a strict sequence for HIV testing. The initial screening uses a 4th-generation antigen/antibody combination assay. If reactive, a supplemental HIV-1/HIV-2 antibody differentiation assay is performed. If the differentiation assay is negative or indeterminate (which is common in early acute infection, such as 3 weeks post-exposure), an HIV-1 nucleic acid test (NAT) must be ordered to directly detect viral RNA and establish the diagnosis. Once the diagnosis is confirmed, baseline labs including a CD4 count and resistance testing are ordered to guide treatment.

Adım Adım Çözüm

1
Identify the appropriate initial screening test for HIV.
Select the 4th-generation HIV-1/2 antigen/antibody combination immunoassay.
This is the universally recommended first laboratory step to screen for HIV because it detects both early (p24 antigen) and established (antibodies) infection.
2
Determine the required follow-up test for a reactive initial screening result.
Select the HIV-1/HIV-2 antibody differentiation immunoassay.
This test confirms the initial reactive result and differentiates between HIV-1 and HIV-2, which is critical for guiding subsequent therapy.
3
Address the possibility of an indeterminate or negative differentiation result due to the patient's recent high-risk exposure (3 weeks ago).
Select the HIV-1 nucleic acid amplification test (NAT).
In acute HIV infection, the differentiation assay may fail to detect immature antibody responses. NAT definitively identifies the presence of viral RNA in the blood.
4
Determine the appropriate post-diagnostic management laboratory steps.
Select the baseline CD4+ T-lymphocyte count and genotypic resistance profile.
Once the diagnosis of HIV is established, baseline immunologic and virologic parameters must be assessed before prescribing antiretroviral therapy.

Anahtar Kavram

Standard HIV diagnostic algorithm and test sequencing for acute infection
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Ordering Laboratory Tests

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