Diagnostic Assays in Infectious Disease Flashcards
- the extent to which the test is accurate for those who have the disease in question
- avoiding false negatives
- sensitivity
- the extent to which the test is accurate for those who do not have the disease in question
- avoid false positives
- specificity
- the extent to which a positive test indicates presence of disease
- positive predictive value
- the extent to which a negative test indicates absence of disease
- negative predictive value
specimens in light microscopy
- may be fresh or stained
sensitivity in light microscopy
- often low
specificity in light microscopy
- depends on organisms and specimens
sensitivity of culture
- higher than microscopy
- lower than NAATs
viral culture requires
- eukaryotic host cells
immunoassays involve
- antigens and antibodies
formats of Immunoassays
- ELISA
- Western Blot
- Rapid immunochromatographic strip tests
- particle agglutination tests
antigen detection test requires
- specific antibodies
primary detection antibody recognizes
- same antigen but not same epitope
secondary detection antibody recognizes
- Fc portion of primary antibody
- has signal on it
indicators of current infection
- antigen detection tests
indicators of past infection
- antibody detection tests
sensitivity vs specificity most influences test performance in low organism burden
- sensitivity
sensitivity vs specificity most influences test performance in potential detection of closely related organisms
- specificity
sensitivity vs specificity most influences test performance in too little specimen
- sensitivity
sensitivity vs specificity most influences test performance in low prevalence populations
- specificity
accuracy
- telling the truth
precision
- telling the same story over and over again
PPV of highly specific and sensitive test in high prevalence population
- high
PPV of highly specific and sensitive test in low prevalence population
- low
NAAT
- molecular detection assays for bacteria, viruses, and eukaryotic pathogens
NAAT targets
- microbial DNA and RNA
NAAT amplification
- enzymatic amplification of target molecules
NAAT sensitivity
- more sensitive than microscopy, culture, or antigen detection
NAAT specificity
- more specific for nucleotide sequences
NAAT live organisms
- doesn’t require live organisms
NAAT consequences with detection of dead organisms
- impacts timing of test of cure
- tests may remain positive for days-weeks after treatment
- false positive
NAAT increased sensitive allows testing with
- non-invasive pathogens
- using a urine test for STI’s instead of endocervical swab.
antimicrobial susceptibility testing depends on
- in vitro testing with live organisms grown in presence of antimicrobial agents
- culture