Clin Lab: STIs Flashcards
Note
Many STIs can be asymp & are often underdx
Undx infx can lead to what significant complications in females?
PID & infertility
List common STIs
Chancroid
Chlamydia
Gonorrhea
Genital warts / HPV
Hepatitis A/B/C
Herpes simplex
HIV
Syphilis
Mycoplasma genitalium
Scabies and crab louse
Syphilis
Trichomonas
What is commonly tested/route for STIs
serum & wet prep/urine
We test serum for which STIs?
- HIV
- Syphilis
- Hep A/B/C
We test wet prep/urine for which STIs?
- Gonorrhea
- Chlamydia
- Trichomonas
Who do we test for HIV?
Everyone!!!
- Suspected acute infx
- Those at incr risk – yearly, maybe even quarterly
- All adults at least once
- All pregnant women, each pregnancy
What are some S/Sx of a suspected HIV acute infx pt?
Flu-like symptoms, sore throat in the right person
When do we test pregnant women for HIV?
at their first prenatal visit
What is the best test to detect HIV and how long is the window?
- RNA
- 5-7 days
What can diagnostics tests for HIV detect?
- antibodies against HIV 1 or 2
- HIV p24 antigen
- HIV-1 RNA*
NOTE
Different HIV tests are used depending on acute infection vs chronic infection vs screening
Screening test for HIV
- 3rd gen immunoassay
- 4th gen immunoassay
What does the 3rd gen immunoassay for HIV measure?
Abs only
- IgG and IgM Abs
What does the 4th gen immunoassay for HIV measure?
Ab & PRO Ag
- IgG/IgM and P24 Ag
What are the FU tests/confirmatory test if HIV screening test is (+)?
- HIV-1/HIV-2 Ab differentiation assay
- HIV-1 RNA
- Older -> Western blot (PRO electrophoresis)(HIV-1)
Further diagnostic testing in pts w/ HIV
- CD4 T-Lymphocyte Count
- HIV-RNA quantification (viral load)
- Phenotypic & Genotypic Assays for Antiretroviral Drug Resistance
Diagnostic tests for acute HIV infx
- 4th gen assay
AND - HIV-1 RNA test
Often have (-) assay & (+) RNA test in acute infx
If both are (-)& there is high suspicion of infx, repeat in 1-2 wks
Laboratory Testing for HIV flow chart
DONE
Recommended Initial Tests: Dx of chronic HIV infx or screening in asymp ppl
4th gen assay
Recommended Initial Tests: Dx of acute HIV infx
4th generation assay & HIV-RNA detection
Recommended Initial Tests: Dx of HIV in infants born to HIV-infected mother
DNA PCR or HIV-RNA detection
Recommended Initial Tests: Prognosis
HIV-RNA quant & CD4 T-cell count
Recommended Initial Tests: Response to antiretroviral therapy
HIV-RNA quant & CD4 T-cell count
Recommended Initial Test: Antiretroviral drug resistance testing
Phenotypic and/or genotypic resistance assays
Recommended Initial Tests: blood donor screening
3rd gen assay & HIV-RNA detection
How is Hep B tested?
measure Hep B surface antigen, surface antibody &core antibody
Hep B Testing Results Chart
(Phase (5), HBsAg, Anti-HBc, IgM Anti-HBc, Anti-HBs)
DONE
Describe testing interpretation for Hep C
- If (-), chronic infx is unlikely
- If (+), measure Hep C RNA (PCR)
–> If (+), chronic infx confirmed–> tx
Who do we screen for Hep B/C?
higher risk patients
What do we measure for Hep C testing
Hep C Antibodies (anti-Hep C)
Describe Hep C test interpretation
- If (-), chronic infx is unlikely
- If (+), measure Hepatitis C RNA (PCR)
–>If (-), chronic infx unlikely
–> If (+), chronic infx confirmed–> tx
What 2 tests can be done to detect syphilis?
- Direct visualization
- Antibody testing
Describe the protocol/results of the two antibody tests for syphilis?
- If initial test is (-), no further testing is needed unless high suspicion for infx
- If initial test is (+), need to do the other type of antibody test for confirmation
–> Do test of opposite type: (+)/(+) tx for syphillis
Syphilis antibodies are usually detected by…
serum
Which STI requires testing of the CSF?
neurosyphilis
Name the 2 types of syphilis antibody test
Non-treponemal tests & Treponemal tests
Non-treponemal test detects…
serum reagin antibodies
What antigens are associated w/ non-treponemal testing?
cardiolipin/cholesterol
What happens to the non-treponemal titer as infx is resolved over time?
it decreases
What are the types of non-treponemal tests?
- Rapid plasma reagin (RPR)
- Venereal Dz Research Lab (VDRL)
Treponemal test detects…
antibodies against treponemal antigens
What happens to the treponemal titer?
remains (+) after infx resolved
What are the types of treponemal tests?
- FTA-ABS (Fluorescent Treponemal Antibody – absorbed)
- TP- EIA (T palladium ELISA)
If (-) non-treponemal (RPR or VDRL) test, what happens next?
no further testing necessary, unless strong suspicion for either very early primary infx or latent infx
If (-) treponemal (FTA-APS or TP-EIA), what happens next?
no further testing considered necessary
If either the non-treponemal/treponemal test is (+), what happens next?
perform confirmatory test of opposite type
(+) non-treponemal + high titer / positive treponemal means…
syphilis infx
(+) initial non-treponemal + low titer / negative FU treponemal means…
likely initial false (+)
(+) initial treponemal + (-) FU non-treponemal means…
either
- prior tx infx
- very early primary infx
- late infx
Syphilis screening flow chart
DONE
What organism causes Chlamydia?
Chlamydia trachomatis