Lab Diagnosis of Infectious Disease

what is a method for detecting bacteria that relies on growing organisms in vitro, typically taking 48-72 hours for common bacteria, and sometimes longer for slow-growing organisms?

culture

what is the ability of a test to correctly identify the presence of a specific pathogen?

sensitivity

what is the ability of a test to correctly identify the absence of a specific pathogen?

specificity

what is the time it takes to get results from a diagnostic test?

turnaround time

what is a category of tests that can be performed quickly and are relatively inexpensive, including immunochromatographic assays and ELISA tests?

antigen detection

what is a category of tests that are becoming the preferred method for detecting certain organisms due to their increased sensitivity and specificity, and are used for fastidious, slow-growing, or difficult-to-culture pathogens?

molecular-based assays

what is a method for diagnosis that has been used historically to confirm infections with bacteria that are difficult to grow and involves the detection of specific antibodies in a specimen, usually serum?

serological diagnosis

what is a major disadvantage of the Gram stain?

it cannot detect viruses, fungi, parasites, and certain bacteria like Mycobacteria and Chlamydia

what are the advantages of antigen detection tests?

rapid, inexpensive, and easy to perform

what are the limitations of some antigen detection assays?

they can have poor sensitivity and limited availability for some pathogens

what are the advantages of molecular methods over culture?

increased sensitivity and specificity, more rapid identification of fastidious or slow-growing organisms

what are the disadvantages of molecular methods?

false-positives due to contamination, false-negatives if inhibitors are present in the specimen

what is a limitation of molecular methods regarding antimicrobial susceptibility?

organisms still need to be cultured to perform antimicrobial susceptibility testing (AST)