The diagnostic test used to detect Human Immunodeficiency Virus (HIV) is ELISA.

ELISA, or Enzyme-Linked Immunosorbent Assay, is the standard screening test for HIV because it sensitively detects antibodies produced by the body in response to the virus.

Option Breakdown

(A) Widal

Widal test diagnoses typhoid fever by detecting antibodies against Salmonella typhi bacteria, such as O and H antigens via agglutination. It has no role in HIV detection, as HIV is a retrovirus, not a bacterial infection.

(B) Autoradiography

Autoradiography visualizes radioactive-labeled molecules in research, like detecting DNA bands in gels. It is not a clinical diagnostic for HIV, lacking the specificity and speed needed for routine screening.​

(C) ELISA

ELISA uses enzyme-linked antibodies to detect HIV-specific antibodies or antigens in blood, producing a color change measurable by spectrophotometry. It serves as the primary, highly sensitive HIV screening test, often confirmed by Western blot.

(D) Precipitation

Precipitation tests form visible antigen-antibody complexes, used in some older serology assays. They lack ELISA’s sensitivity and are not standard for HIV diagnosis.​

The diagnostic test used to detect Human Immunodeficiency Virus (HIV) is ELISA, a cornerstone in HIV screening worldwide. This multiple-choice question—covering options like Widal, Autoradiography, Precipitation—tests core microbiology knowledge for exams in biology, medicine, and life sciences.

Why ELISA for HIV Detection?

ELISA excels in detecting HIV antibodies or p24 antigen through enzyme-amplified signals on a solid phase, offering high sensitivity for early screening. Positive results prompt confirmatory tests like Western blot or PCR, ensuring accuracy in clinical settings.

Analyzing Incorrect Options

• Widal Test: Targets typhoid via Salmonella agglutinins; irrelevant for viral HIV.

• Autoradiography: Research tool for radiolabeled imaging, not patient diagnostics.​

• Precipitation: Basic immunology reaction, outperformed by ELISA’s precision.​

This breakdown clarifies why ELISA is the correct choice (C) for the diagnostic test used to detect Human Immunodeficiency Virus (HIV).​