LAB MEDICINE Flashcards
pinworm prep
- apply tape over butthole and examine under microscope
- positive if eggs or adult worms present
blood culture
- looks for systemic infection
- 24-48hrs for bacteria detection
- biochem/microscopic test to identify bacteria
- should come from a sterile source
sputum culture gram stain
- used when pneumonia/TB are suspected
- must be SPUTUM
- not sensitive or specific for S. pneumonia
wound culture and sensitivity (aerobic/anaerobic)
- find out if wound is infected; ID of bacteria; see if tx is working
- absence of bacteria doesn’t rule out infection
- anaerobes often in wounds; may be mult. organisms
viral culture/fluorescent microscopy
- requires cell culture (bc viruses don’t replicate on their own)
- CPE=cytopathic effect (change in appearance of infected cells)
acid fast bacilli stain (AFB)
- ID of mycobacterium (aerobic, acid fast rods)
- M. tuberculosis and M. leprae two big ones
stool for ova and parasite
- look for cysts (formed stool) or trophozoites (diaggheal stools)
- 3 samples needed
- cysts need wet mount (saline, iodine, trichrome stains)
cold agglutinin
- serum test to detect Mycoplasma pneumoniae (atypical pneumonia)
- pos or neg result (doesnt tell you the organism)
- pts with M. pneumoniae develop autoimmune antibodies that agglutinate in the cold
Enterotest for giardia
- aka “string” test: swallow capsule w/ string attached, tape string to cheek, string withdrawn
- look at string (trophozoites adhere to string)
thick and thin blood smear
- diagnosis of malaria
- differentiate between morph. characteristics of each species
- mixed infections of diff plasmodium may occur
KOH preparation
- skin scraping, sputum, lung biopsy
- KOH destroys most things other than fungus
- stain CRYPTOCOCCUS NEOFORMANS with india ink
throat culture
- gold standard for strep throat
- 24-48hrs for results
- single swab–90-95% sensitive
urine culture and sensitivity
- used when pyelonephritis or cystitis is suspected
- E. coli MOST common
- clean catch, cath sample, suprapubic aspirate
- count of 100,000/mL for dx of bacteriuria
- tx is broad empirically then narrowed after sensitivity test
fungal culture
-thermally dimorphic fungi: form diff. structures at diff. temps
-Sabouraud’s agar
slow growing fungi apparent bc of inhibited bacterial growth
supports fungal growth for several weeks
-DNA probe (ID colonies earlier)
gram stain
-
mycoplasma serology
- Mycoplasma pneumoniae (atypical pneumonia)
- cant gram stain this bc NO CELL WALL
stool culture
- used for enterocolitis
- direct microscopic exam of stool:
- methylene blue shows leukocytes (invasive org. present–infectious cause)
- gram stains not routine (too much bacteria already there)
nucleic acid amplification tests (NAAT)
-PCR (many specimen types) and ligase chain reaction tests (urine)
polymerase chain reaction test (PCR)
- most frequently used NAAT
- used to detect microbiologic organisms
- amplifies normal DNA replication
- ID on agarose gel electrophoresis
ligase chain reaction test
- another type of NAAT-relatively new
- greater specificity than PCR
- can see C. trachomatus and N. gonorrhoeae in URINE
RPR
- syphilis
- non treponemal antibody test
- good for SCREENING
- non specific (high false pos)
- any pos result confirmed by FTA-ABS or MHA-TP
VDRL
- syphilis
- non treponemal antibody test
- good for SCREENING
- non specific (high false pos)
- any pos result confirmed by FTA-ABS or MHA-TP
ELISA
- initial screening test to detect HIV antibodies
- high spec and sens but still need confirmatory test for diagnosis
dark-field microscopy
- direct detection for pt w/ suspicious genital/skin lesion
- look for motile spiral shaped organisms (syphilis)
FTA-ABS
- syphilis
- florescent treponemal antibody test
- confirmatory test after screening test
MHA-TP
- syphilis
- microhemagglutination
- test for treponemal antibodies
- confirmatory test post screening test
Western blot
- confirmatory test for HIV antibodies
- results=positive, indeterminate, negative
- highly specific
what lab test do you do to determine rubella immunity?
-serology
what lab test do you do to determine hep B immunity?
-serology
what lab test do you do to determine PPD/TB immunity?
-mantoux or tuberculin skin test
what test do you do to determine varicella immunity?
-serology
CSF Cultures
- used when meningitis is suspected
- acute meningitis: N. meningitidis, S. pneumoniae, H. influenzae
- sub acute meningitis: M. tuberculosis (acid fast stain) and Cryptococcus neoformans (fungus–INDIA INK!)
direct microscopy for fungal ID
- specimens like sputum, lung biopsy, CSF, skin scrapings
- india ink stain for which fungus?!
