36.1 CASE STUDY

A 28-year-old man had several complaints. He had a bad case of thrush (oral candidiasis) and low-grade fever, had serious bouts of diarrhea, had lost 20 pounds in the past year without dieting, and, most seriously, complained of difficulty breathing. His lungs showed a bilateral infiltrate on radiographic examination, characteristic ofĀ P. cariniiĀ pneumonia. A stool sample was positive forĀ GiardiaĀ organisms. He was a heroin addict and admitted to sharing needles.


What laboratory tests should have been done to support and confirm a diagnosis of HIV infection and AIDS?

Exactly, the patient's symptoms are indicative of severe immunosuppression and are characteristic of advanced HIV infection, often referred to as AIDS (Acquired Immunodeficiency Syndrome).

To support and confirm a diagnosis of HIV infection and progression to AIDS:

HIV Antibody Testing:

  • ELISA (Enzyme-Linked Immunosorbent Assay): This is the initial screening test for HIV. It detects antibodies produced in response to the HIV infection.

  • Western Blot or Immunofluorescence Assay (IFA):If the ELISA test is positive, it is typically followed by a Western blot or IFA to confirm the diagnosis.

Direct Detection of the Virus:

  • PCR (Polymerase Chain Reaction): This test detects the genetic material of the HIV virus itself. It's especially useful in certain situations, such as in cases of recent infection when antibodies might not have developed yet or in newborns where maternal antibodies can interfere with testing.

CD4 T Cell Count:

  • A CD4 T cell count using flow cytometry will determine the number of CD4 T cells in the blood. A count less than 200 cells per microliter is one of the criteria for the diagnosis of AIDS.

Viral Load Test:

  • This measures the amount of virus in the blood and can give a good indication of how active the virus is and the progression of the disease.

Other tests:

Given the patient's symptoms, other tests might be ordered to check for opportunistic infections, like cultures or specific staining for Pneumocystis carinii, or tests for Giardia.

The history of intravenous drug use and sharing needles puts this individual at a high risk for HIV transmission. When coupled with the clinical signs and the presence of opportunistic infections (like P. carinii pneumonia and oral candidiasis), HIV infection leading to AIDS becomes a primary consideration.

Mind Map: Diagnosis of HIV Infection and AIDS

HIV Antibody Testing

  • ELISA (Enzyme-Linked Immunosorbent Assay)

    • Initial screening test for HIV

    • Detects antibodies produced in response to HIV infection

  • Western Blot or Immunofluorescence Assay (IFA)

    • Confirms the diagnosis if ELISA test is positive

Direct Detection of the Virus

  • PCR (Polymerase Chain Reaction)

    • Detects the genetic material of the HIV virus

    • Useful in cases of recent infection or interference from maternal antibodies

CD4 T Cell Count

  • Determines the number of CD4 T cells in the blood

  • Count less than 200 cells per microliter is a criterion for AIDS diagnosis

Viral Load Test

  • Measures the amount of virus in the blood

  • Indicates the activity and progression of the disease

Other Tests

  • Opportunistic Infections

    • Cultures or specific staining for Pneumocystis carinii

    • Tests for Giardia

  • Intravenous Drug Use History

    • High risk for HIV transmission

    • Coupled with clinical signs and opportunistic infections, suggests HIV infection leading to AIDS