MKSAP Quiz: Establishing care for HIV
A 31-year-old man arrives to establish care for newly diagnosed HIV infection. He is asymptomatic. Medical history is otherwise noncontributory, and he takes no medications. Following a physical exam and review of lab studies, what is the most appropriate next step in management?
A 31-year-old man arrives to establish care for newly diagnosed HIV infection. He is asymptomatic. Medical history is otherwise noncontributory, and he takes no medications.
On physical examination, vital signs are normal, and the remainder of the examination is unremarkable.
A review of his previous laboratory studies shows a normal complete blood count, and chemistries, including glucose, creatinine, and liver enzyme levels, are within normal limits. The HIV-1/2 antigen/antibody combination immunoassay is reactive. The HIV-1/2 antibody differentiation assay is positive for HIV-1 antibody, and HIV-1 RNA is quantified at 27,313 copies/mL. CD4 cell count is 455/µL.
Which of the following is the most appropriate next step in management?
A. Genotypic viral resistance testing
B. Glycohemoglobin level
C. Phenotypic viral resistance testing
D. Repeat HIV viral load and CD4 cell count in 1 month
MKSAP Answer and Critique
The correct answer is A. Genotypic viral resistance testing. This content is available to MKSAP 18 subscribers as Question 30 in the Infectious Disease section. More information about MKSAP is available online.
This patient needs baseline genotypic HIV resistance testing. Because of the possibility of transmitted virus having resistance mutations, it is recommended to obtain baseline resistance testing before starting an antiretroviral regimen. If the patient is ready, antiretrovirals can be started the same day, while waiting for resistance testing results, with regimen modification if necessary based on results. Virologic failure of a regimen (rebound of a suppressed viral load or failure to achieve undetectable viral load with therapy) is also an indication for resistance testing to guide the change in regimen. Genotypic testing looks for mutations in the viral genome associated with antiviral drug resistance. Phenotypic testing actually tests the virus's ability to grow in the presence of differing concentrations of the drug and is therefore more useful in the presence of multiple interacting mutations or unclear correlations of mutation and resistance, such as occurs with resistance to protease inhibitors. Genotypic testing is faster and less expensive because all that is necessary is sequencing of the respective genes for the patient's viral isolate. When significant resistance is not expected and information is needed more quickly, genotypic testing would be preferred over phenotypic testing.
Some antiretroviral agents have been associated with increased insulin resistance and risk for hyperglycemia, and assessing for this at baseline and during therapy is recommended. This patient, however, already has a normal glucose level at baseline testing, so measuring the glycohemoglobin is not necessary at this time.
All patients with HIV should begin antiretroviral therapy as soon as they are ready. Prompt initiation of therapy benefits the patient and reduces the risk of transmission to others, so waiting for repeat viral load and CD4 cell count is inappropriate and unnecessary.
Key Point
- Genotypic viral resistance testing is recommended immediately after a diagnosis of HIV infection to guide the selection of active agents for the antiretroviral regimen or after virologic failure of a regimen to guide adjustment of antiretroviral therapy.