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
Describe chlamydia trachomatis
Intracellular (GNID) pathogen of columnar epithelial cells
Is chlamydia a urogenital infx?
YES usually, but can cause non-urogenital infx…
- conjunctivitis, pharyngitis, reactive arthritis, proctitis, lymphogranuloma venerum
S/Sx of chlamydia
usually asymp
–> can have burning during urination &/or discharge
Testing for chlamydia & describe how it is obtained
- NAAT
–> First-catch urine in men - vag/endocervical swab in women
Describe Neisseria gonorrhea.
intracellular pathogen
–> gram (-) intracellular diplococci
2 diagnostic tests for N. gonorrhea
- NAAT
- Gram stain & culture
Describe N. gonorrhea gram stain & culture for males
- gram stain of urethral exudate
–>If Gram stain(+) for GNID = def dx
First catch urine
Describe N. gonorrhea gram stain & culture for females
DON’T use gram stain of vaginal discharge
- use endocervical swab
- (+) GNID = presumptive diagnosis in female
Confirm w/ culture results
What type of infx is gonorrhea?
non-urogenital
Gonorrhea can cause which type of conditions(5)?
- conjunctivitis
- proctitis
- pharyngitis
- disseminated gonorrhea
- septic arthritis
Testing for gonorrhea
- NAAT testing
- Gram stain / culture (in some instances)
What specimens can be used for gram stain/culture?
- Synovial fluid
- Blood cultures
- Eye
Site of disseminated gonorrhea.
- joints (purulent septic arthritis)
- heart (endocarditis)
- bone (osteomyelitis)
- brain (meningitis)
Describe ailments of disseminated syndrome of gonorrhea.
- arthritis-dermatitis
- tenosynovitis,
- migratory polyarthritis
- painless skin pustules
- often with fever/malaise as well
List the prevalence of gonorrhea/chlamydia/mycoplasma genitalium (highest - lowest)
Mycoplasma genitalium is a major cause of…
non-gonococcal urethritis
How will a patient present w/ mycoplasma genitalium?
The same as a person w/ gonorrhea-chlamydia, but their testing will be (-) for those conditions
Who do we test for mycoplasma genitalium?
anyone who you are testing for Gonorrhea/Chlamydia
Testing for Mycoplasma genitalium
(men vs women)
NAAT
- first-catch urine for men
- vaginal swab for women
Which herpes virus can cause genital herpes?
HSV 1 & 2
Which HSV virus is more likely to cause oral herpes?
HSV-1
Which HSV virus is more likely to cause genital herpes?
HSV-2
How is HSV usually diagnosed?
clinical dx
How does a HSV rash look?
Painful, grouped vesicles, on erythematous base
Describe testing methods for HSV
- Tzanck prep–> unroof young vesicle–> multi nucleated cells
- Cell culture from early vesicular lesion gold standard
- Viral PCR from lesion swab*
- Direct fluorescent testing
- Serum Ab testing
Which HSV test can detect asymptomatic shedding of the virus?
viral PCR from lesion swab
What is the most common STD in the US & the world
Human Papilloma Virus (HPV)
What % of sexually active adults have been infected w/ HPV?
> 75%
HPV is associated w/ what conditions?
ano/genital dysplasia & epithelial (squamous cell) CAs
What conditions can HPV cause?
- Condylomata accuminata (genital warts)–> non-CA
- Cervical CA
- Oropharyngeal CA
HPV diagnostics
limited to cervical specimens
What other testing can be done for HPV?
testing CA samples for HPV DNA
What vaccine can be used to protect against strains of HPV & most likely ones to causes cervical cancer?
Gardasil
What is the most common non-viral, non-bacterial STI in the US?
trichomoniasis
What organism causes trichomoniasis?
Trichomonas vaginalis
What are the testing options for Trichomoniasis?
- direct visualization on wet prep
- culture
- Rapid antigen tests
- NAAT
NOTE
You have to see the trichomonas vaginalis & you have to see it moving to say its (+)
How long does a trichomoniasis culture take?
about 48 hours
What is the GS testing for trichomoniasis?
NAAT
What is Leptothrix?
long bacteria often present with trichomonas
–> if seen you should also check for trichomonas vaginalis
Is chancroid rare or common?
RARE
Describe a chancroid.
Genital ulcers, often necrotic or erosive and painful
What differentiates a chancroid ulcer from syphilis ulcer?
- chancroid is painful
- syphilis is painless
Testing for chancroid
- Culture
- PCR
(only available through regional labs)
Organism that causes crab louse
Pthirus pubis
Crab louse dz is called…
Pediculosis pubis
How does crab louse (pthirus pubis) survive?
feeds on human blood
How will a pt present w/ crab louse?
itching
Does crabs louse embed in the skin or stay on the surface?
stays on surface
- eggs are on the pubic hairs
Crab Louse Dx
visualization of louse or eggs
What organism causes scabies?
Sarcoptes scabiei
Describe a scabies rash
Pruritic papular rash
Does scabies embed in the skin or stay on the surface?
embedded into skin
Scabies Dx
skin scraping
Indications for a vaginal wet prep
- Vaginal discharge/odor
- Vulvar or vaginal itching
- Vaginal or lower abdo pain
Describe the vaginal wet prep procedure
- Cotton swab used to get sample of vaginal discharge/cervix
- Swab placed in test tube in several drops of saline
- One drop is placed on slide w/ coverslip & examined w/ light microscope
- KOH test
Which part of the vagina should you exam for wet prep and why?
Look at posterior fornix for any pooling of discharge or clumps
Vaginal wet prep will give you the following results…
- epithelial cells/types
- WBCs
- Evidence of infx
What are the layers of vaginal epithelium? (outer to inner)
- superficial cells
- Intermediate cells
- Parabasal cells
- Basal cells
Describe what seen w/ Superficial Squamous Epithelium
- Normal Squamous Epithelium
- Normal Flora (lactobacilli)
- a few WBCs
Describe to look of Superficial Squamous Epithelium
- “fried eggs”
- irregular borders
- Mostly cytoplasm, nucleus appears small
Parabasal squamous epithelium is seen in…
- estrogen deficiency
- traumatic exfoliation of vaginal lining
-vaginal wall atrophy
Parabasal Squamous Epithelium are similar to what cells in the kidney system?
transitional cells
Seeing basal squamous epithelium indicates…
extremely atrophic or deeply ulcerated vaginal mucosa
Describe basal squamous epithelium
Simple cuboidal cells
–> when free they look more rounded
Basal Squamous Epithelium are similar to what cells in the kidney system?
renal tubular epithelial cells
Which organisms elicit an immune response?
- Trichomonas
- Candida
- Herpes
- Gonorrhea
- Chlamydia
Which bacteria does NOT cause an immune response?
Gardnerella vaginalis
What is the most common cause of a yeast infx?
candida albicans
Describe what is seen when a person has a yeast infx?
- budding yeast &/or hyphae
- Small amount normally found; overgrowth is infx
Is a yeast infx an STI?
NO
Testing used for a yeast vaginal infx?
KOH test
What bacteria causes bacterial vaginosis?
Gardnerella vaginalis
Describe bacterial vaginosis.
NOT an STI
- an overgrowth of normal flora
Does bacterial vaginosis have a WBC response?
NO
Testing proof of bacterial vaginosis
“Clue cells”
Bacterial vaginosis can result in…
urethritis
Describe clue cells
bacteria attaches itself to the squamous cells & obscures the edges; looks sandy in appearance
What can be the cause of whitish clumps & vaginal itching not due to yeast infx?
- azithromycin
- douching
What is actually causing the white clumps not caused by yeast infx?
sheets of squamous epithelial cells
