Infections & Immunity

Screening for infections and checking immunity from past infection or vaccination.

53 tests explained

Common follow-up tests

Antistreptolysin O (ASO) titerMeasures antibodies your body makes against a toxin from group A strep bacteria, which can show a strep infection in the recent past.
Chlamydia trachomatis NAATA urine test that looks for the genetic material of the bacteria that cause chlamydia, a common sexually transmitted infection.
Cytomegalovirus (CMV) IgGA blood test for antibodies that show whether your immune system has met cytomegalovirus (CMV), a very common virus, at some point in your life.
Cytomegalovirus (CMV) IgMLooks for IgM antibodies that often appear early in a new CMV infection, but can also stay positive for months or come back falsely positive.
Dengue NS1 antigenDetects a dengue virus protein in the blood during the first days of illness, which can show an early, current dengue infection.
Dengue virus IgGLooks for IgG antibodies that show whether your immune system has met a dengue virus before, but it cannot date the infection.
Dengue virus IgMA blood test for IgM antibodies against the dengue virus, used to look for a recent dengue infection.
Diphtheria antitoxoid IgGMeasures antibodies against the diphtheria toxin to show whether vaccination or past exposure still gives you protection.
EBV nuclear antigen (EBNA) IgGAn antibody that appears months after Epstein-Barr virus infection and stays for life, so a positive result usually points to an infection in the past.
EBV viral capsid antigen (VCA) IgGAn antibody to Epstein-Barr virus that appears in a first infection and then stays for life, so it shows whether you have ever been infected.
EBV viral capsid antigen (VCA) IgMAn early antibody to Epstein-Barr virus that is often present during a first infection and fades within weeks to a few months.
Hepatitis A antibody, IgMAn early antibody to the hepatitis A virus. A positive result can mean a current or recent hepatitis A infection.
Hepatitis A antibody, totalMeasures all hepatitis A antibodies (IgG and IgM) together. A positive result usually means you are immune from a past infection or the vaccine.
Hepatitis B Core Antibody, IgMA short-lived antibody that appears early in a new hepatitis B infection. A positive result is linked to infection within roughly the past six months.
Hepatitis B Core Antibody, Total (Anti-HBc)An antibody your body makes after hepatitis B infection. A positive result is linked to past or current infection. The vaccine does not cause it.
Hepatitis B e antibody (anti-HBe)An antibody to the hepatitis B e antigen. In someone with hepatitis B, a positive result is often linked to the virus being less active.
Hepatitis B e antigen (HBeAg)A hepatitis B virus protein linked to active virus growth and higher infectiousness. It's usually checked only after a positive HBsAg.
Hepatitis B Surface Antibody (Anti-HBs)The antibody that protects against hepatitis B. A result of 10 mIU/mL or higher is generally treated as protected, from vaccination or past infection.
Hepatitis B Surface Antigen (HBsAg)A protein from the hepatitis B virus. A positive result is linked to the virus being in your blood now, from a recent infection or a long-term one.
Hepatitis B Virus DNA (Quantitative)Measures how much hepatitis B virus DNA is in your blood. It helps show how active a long-term hepatitis B infection is.
Hepatitis C AntibodyChecks for antibodies your immune system makes after hepatitis C exposure. A reactive result is followed by an RNA test to see if the virus is still there.
Hepatitis C Virus GenotypeShows which type (genotype) of hepatitis C virus you have. It is usually done once and can help your clinician plan treatment.
Hepatitis C Virus RNA (Quantitative)Measures how much hepatitis C virus genetic material (RNA) is in your blood. It shows whether the virus is present now and how treatment is going.
Herpes Simplex Virus 1 IgG (Type-Specific)Looks for IgG antibodies to herpes simplex virus type 1 (HSV-1), the usual cause of cold sores. A positive result means you were infected at some point.
Herpes Simplex Virus 2 IgG (Type-Specific)Looks for IgG antibodies to herpes simplex virus type 2 (HSV-2), a common cause of genital herpes. A low positive result often needs a second test to confirm.
HIV-1 RNA (Quantitative Viral Load)Measures how much HIV-1 genetic material (RNA) is in a blood sample. It shows how well HIV treatment is working.
HIV-1/2 Antigen/Antibody (4th Generation)A blood test that looks for HIV antibodies and a viral protein (p24), so it can find an infection earlier than tests that only look for antibodies.
Lyme Disease Antibody (Screen)A first-step blood test for antibodies to the bacteria that cause Lyme disease. A positive or equivocal result is followed by a second test.
Lyme Disease Western Blot (IgG and IgM Bands)A blood test that checks which Lyme bacteria proteins your antibodies react to. It is the second step after a positive or equivocal antibody screen.
Malaria Antigen (Rapid Test)A quick finger-prick or blood-draw test that looks for proteins from malaria parasites. In the US, a positive or negative result is followed up with a blood smear.
Malaria Parasite Smear (Thick/Thin Film)A microscope exam of a blood sample that shows whether malaria parasites are present, which species they are and how many red cells are infected.
Measles (Rubeola) IgGChecks for antibodies that show your body has met the measles virus, through vaccination or past infection. It is often used to check immunity.
Mononucleosis Screen (Heterophile Antibody)A quick blood test for heterophile antibodies, which most often appear during infectious mononucleosis (mono), usually caused by the Epstein-Barr virus.
Mumps IgGAntibodies that show your immune system has met the mumps virus, from the MMR vaccine or a past infection. Results are usually printed as negative, equivocal or positive.
Neisseria gonorrhoeae NAATA urine test that looks for the genetic material of the bacteria that cause gonorrhea, a common sexually transmitted infection.
QuantiFERON-TB Gold Plus (IGRA)A blood test that shows whether your immune system has reacted to TB bacteria. It cannot tell a dormant infection from active TB disease.
RPR (Rapid Plasma Reagin)A blood test used to help find syphilis and to follow its treatment. A reactive result needs a second, more specific test to confirm it.
Rubella IgGShows whether you have antibodies to the rubella (German measles) virus, from vaccination or past infection. Often checked before or early in pregnancy.
Salmonella Typhi IgM (Typhoid Antibody)A blood test for IgM antibodies to the typhoid bacterium. On its own it cannot confirm typhoid fever.
SARS-CoV-2 nucleocapsid (N) antibodyChecks for antibodies to a protein inside the COVID-19 virus. A positive result can be a sign of a past infection.
SARS-CoV-2 spike (S) antibodyMeasures antibodies to the virus's spike protein, which rise after COVID-19 vaccination or infection. No number is a proven sign of protection.
Syphilis Antibody, TreponemalLooks for antibodies to the bacterium that causes syphilis. It usually stays positive for life after an infection, even a treated one.
T-SPOT.TB (IGRA result)Counts white blood cells that react to tuberculosis proteins. It shows whether your immune system has met TB bacteria, not whether you are sick.
Tetanus antitoxoid IgGMeasures antibodies against the tetanus toxin to show whether vaccination still gives you protection.
Toxoplasma gondii IgGMeasures long-lasting IgG antibodies to the Toxoplasma parasite. A positive result means past exposure, not necessarily a recent infection.
Toxoplasma gondii IgMLooks for IgM antibodies to the Toxoplasma parasite. They appear early in an infection but can linger for a year or more.
Trichomonas vaginalis NAATA test that looks for the genetic material of Trichomonas vaginalis, the parasite behind trichomoniasis, a common and curable sexually transmitted infection.
Varicella-zoster virus (VZV) IgGA blood test for IgG antibodies to the chickenpox virus, used to check for evidence of past infection or vaccination.
Widal test (typhoid O and H agglutinins)The overall reading of a Widal test, which looks for antibodies to typhoid bacteria. It is easy to misread and cannot confirm typhoid on its own.
Widal, Salmonella Paratyphi A (AH) TiterA Widal test titer for the flagellar (H) antigen of Salmonella Paratyphi A, a relative of the typhoid bacterium.
Widal, Salmonella Paratyphi B (BH) TiterA Widal test titer for the flagellar (H) antigen of Salmonella Paratyphi B, a relative of the typhoid bacterium.
Widal, Salmonella Typhi H TiterA Widal test titer for the typhoid bacterium's H (flagellar) antigen. It can stay raised after an old infection or a vaccine.
Widal, Salmonella Typhi O TiterA Widal test titer for the typhoid bacterium's O antigen. One result cannot confirm or rule out typhoid fever.