Lab med lecture 11

false positive

test incorrectly indicates the presence of a condition when it is not actually present

false negative

test incorrectly indicates the absence of a condition when it is present

sensitivity

how well a test can identify true positive

negative

highly sensitive tests will have a few false --- results

Specificity

how well a test can identify true negatives

positive

highly specific test will have few false --- results

antibodies

proteins produced by the immune system in response to foreign substances. recognizes and binds to antigens

antigen

any substance typically found on the surface of a pathogen, cancer cell, or allergen in which triggers the immune system

IgM

first antibody produced in an acute infection

IgM

this antibody does not provide lasting immunity

IgG

this antibody takes longer to develop but persists to provide lasting immunity

IgG

this antibody suggests previous or chronic infection or immunization

ELISA

which test detects the presence of specific proteins, antibodies or antigens in a sample

ELISA

enzyme linked to an antibody or antigen produces detectable signal when it binds to a target substance. usually changes color once bound

NAAT

molecular test that amplifies the genetic material or pathogens to detectable levels

PCR

what is the most common NAAT

an RNA virus that is an agent of acquired immune deficiency syndrome

what is HIV

retrovirus performs reverse transcription

what is the hallmark feature of HIV

- sexual transmission (MC)

- IV drug use

- transfused blood

- mother child

how is HIV transmitted

- all adults must be screened ONCE

- all pregnant women must be screened every pregnancy

- annual screening for high risk people

what is the criteria for screening for HIV

men and transgender women who have sex with men if they engage in condomless anal sex

who is most likely to get HIV

person who injects drugs

who is most likely to get HIV

people who engage sex for money or drugs

who is most likely to get HIV

people with a sex partner with uncontrolled HIV

who is most likely to get HIV

HIV regions who have unprotected sex

who is most likely to get HIV

HIV immunoassay

what is the gold standard testing agent for HIV

HIV p24

what would show on the HIV test if they are actively infected

HIV-1/HIV-2 differentiation assay

which HIV test can determine the type of HIV

HIV RNA test

what test can detect the qualitative and quantitative measures of HIV

qualitative

presence or absence of viral HIV particles in the blood

quantitative

the number of particles of HIV in the blood

10-12 days after infection

how long does it take for HIV viral RNA levels to be detected on a test

HIV viral RNA levels

what test can you do if you are suspicious for HIV

HIV viral RNA levels

which test for HIV gives us the earliest diagnosis and treatment monitoring

15-20 days after infection

how long does it take for antigen antibody labs for HIV to be detected on a test

antigen antibody lab

what is the test preferred for screening of HIV

Point of Care

what kind of testing must be confirmed with lab testing

first do HIV1/2 antibody antigen test. if its negative its usually true so stop there. if positive, determine the type of HIV.

what are the general rules for screening and diagnosing HIV

if you are concerned for an acute HIV infection or if testing is indeterminate or discordant

when should you do a viral RNA test

CD4 cell counts

what should you look for at diagnosis of HIV

opportunistic infection

what is an increased risk if there is a low CD4

HIV RNA quantification (HIV viral load test)

which test monitors HIV progression and response to the treatment

- jaundice

- dark urine

- pale stool

- RUQ pain

- fever

what are acute sx of viral hepatitis

cirrhosis

what are chronic sx of viral hepatitis

Hepatitis A

which hepatitis is not capable of causing chronic infection

acute infection

which type of infection would this be, acute or chronic?

positive IgM anti HAV antibodies detectable at 2-3 weeks and normalizes at week 8

past exposure and immunity

which type of infection would this be:

IgG HAV antibodies with a negative IgM

HBsAG (HB surface antigen)

which serology detects the first evidence of infection and if persistant >6 months indicates chronic infection

Anti-HBs (antibody against HBsAg)

which serology detects a appearance after the clearance of HBsAg or after successful vaccination

Anti-HBc (antibody against HB core)

which serology appears shortly after HBsAg is detected and can diagnose an infection in the "window" period

HBeAG (HB envelope protein)

which serology appears shortly after HBsAG and represents viral replication and infectivity

Anti-HBeAg (antibody against HBeAG)

which serology signifies diminished viral replication and decreased infectivity

true

True or False:

Vaccination to hepatitis B is against surface antigen prote

True

T/F:

Surface Antigen can be present in acute or chronic infections. Absence indicates patient is either recovered from the infection, never had/doesn't have the infection, or is in the window period

True

T/F:

i-HBcore is useful to distinguish acute and chronic infection in those with a positive surface antigen AND can detect infection in the window period

True

T/F:

HBeAg is indicative of active viral replication/infectivity. Antibody against HBeAg indicates diminished replication/infectivity.

True

T/F:

Those with prior infection will show signs of long-term immunity with IgG against HBc and HBsAg (Anti-HBs)

acute hepatits B

Interpret these labs:HBsAg = Positive, Anti-HBs = Negative, Anti-HBc= IgM positive, IgG negative, HBeAg= Positive, Anti-HBe= negative

chronic hepatitis B

Interpret these labs:HBsAg = Positive, Anti-HBs = Negative, Anti-HBc= IgG positive, IgM negative, HBeAg= Positive, Anti-HBe= negative

Hepatitis B immunity (d/t recovery)

Interpret these labs:HBsAg = Negative, Anti-HBs = Positive, Anti-HBc= IgG positive, IgM negative HBeAg= Negative, Anti-HBe= positive

Hepatitis B immunity (d/t vaccination)

Interpret these labs:HBsAg = Negative, Anti-HBs = Positive, Anti-HBc= IgG= negative, IgM = negative HBeAg= Negative, Anti-HBe= negative

Acute hepatitis B infection: in the window period

Interpret these labs:HBsAg = Negative, Anti-HBs = Negative, Anti-HBc= IgG= negative, IgM = positive HBeAg= positive, Anti-HBe= negative

HCV antibody

what is the screening test used for viral hepatitis C

HCV RNA by PCR

what must you confirm if HCV antibody test is positive

HCV RNA

what is the most sensitive indicator of HCV infection

True

T/F

hep C is capable of causing chronic infection

HSV1

which HSV is most commonly orolabial herpes

HSV2

which HSV is most commonly genital herpes

labratory testing

what does HSV need to be confirmed

viral culture

what is the standard diagnostic method for HSV

PCR

what is a diagnostic method for genital ulcers that have improved sensitivity but are very expensive

Serological tests

what is the diagnostic study used if there are NO active lesions