clinical toxicology Flashcards
quantitative test
- most important?
other examples:
acetaminophen: can find out level, and give antidote if its causing problems. need to know [acetaminophen] to know how to guide treatment.
also presentation of stomach pain could suggest anything. do acetaminophen to rule that out.
alcohols - bad alcohols turn into toxins when metabolized. – osolality, glc, urea also tested to determine toxic alcohol
qualitative test
drugs of abuse in urine. prescription & other drugs.
use immunoassay. , GC/MS, tandem MS
progressive lab testing - qualitative
immunoassays -first, ppresumptive.
then do confirmatory test.
confirmatory tests: specific, expensive: GC/MS, tandem MS. double check because immunoassay sometimes get false positive.
* test can be created specifically for drug when unsure of what drug, or what immunoassay came back negative.
specimens for clinical tox testing
urine : qualitative
serum,blood - quantitative. pharmacokinetics distribute drug into tissue, little found in blood.
gastric aspirates
hair = detect long window of detection.
meconium - baby first poop. expose what mom used/ate in last trimester
why is urine preferred?
in general [ ] of drugs is higher in urine than in blood/serum
easy to collect - usually
metabolite detection is esy
screening assays usually geared towards urine samples
urine limitations
no relationship btw detection & actual ingestion time, amount ingestion, frequncy of use/abuse, degree of impairment.
some drugs have short half life - not detected but cause cause harm if not detected.
adulteration, substitution - test behind closed door - easy to switch sample.
amphetamine immunoassay
not great, ton of false positives.
pseudophedrine = allergy meds related to amphetamine - likely contributes to false positives.
thc metabolite immunoassay
true positive results.
benzodiazepines immunoassay
some false positives, but usually pretty accurate.
opiate immunoassay
morphine, poppy seeds - both trigger (+)
tricyclic antidepressants
very bad immunoassay. alongside amphetamine.
any tricyclic ring will mark this positive.
limitations/problems w immunoassay
false negatives
- cut offs are subjective – in newborns, always do further testing if levels are at 20% of cutoff.
- assay is too specific for one sub-type of the drug, or finds one metabolite when there are more.
- variance in antibody cross-reactivity within drug class - semi-synthetics not picked up. certain variations of drug are missed
one use cartridge based
poct devices are
immunoassays. same false positive/false negative issues
gas chromatograph/mass spectrometer machine
GC component = separates components.
MS each component introduced into MA one molecule at a time. fragment drug molecules to get characteristic spectrum unique to drug. = specific detection
GC/MS spectra analysis
high abundance = informative, high mass (even with low abundance) diagnostically powerful.
