Lab Tests Reference Library

HBsAg is the first marker to appear in Hepatitis B infection. A positive result indicates active Hepatitis B infection (acute or chronic). Screening recommended for all adults at risk.

Anti-HBs indicates immunity to Hepatitis B — either from vaccination or recovery from infection. A level ≥10 IU/L is considered protective immunity.

Anti-HCV detects antibodies against Hepatitis C virus. A positive result requires confirmation with HCV RNA PCR. Hepatitis C can cause chronic liver disease, cirrhosis, and liver cancer.

Fourth-generation HIV test detecting both HIV-1/2 antibodies and p24 antigen. Detects HIV infection as early as 18 days post-exposure. Requires confirmatory testing if reactive.

CD4 count monitors immune function in HIV-positive patients. CD4 <200 cells/µL defines AIDS. Used to guide antiretroviral therapy initiation and prophylaxis decisions.

NS1 antigen is detectable in the first 1–5 days of dengue fever. It is an early marker that helps distinguish dengue from other febrile illnesses during the acute phase.

Dengue IgM appears 4–5 days after symptom onset and persists for 2–3 months. A positive IgM indicates recent dengue infection.

The Widal test detects antibodies against Salmonella typhi antigens. A fourfold rise in titer is significant. Used widely in endemic areas but has limitations in sensitivity/specificity.

Malaria RDT detects Plasmodium antigens in blood. Provides rapid diagnosis in endemic areas. Detects P. falciparum (most dangerous) and other species.