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MLSCI 466 > Clinical Tox Testing > Flashcards

Clinical Tox Testing Flashcards

1
Q

specimens for clinical tox testing

A

urine = specimen of choice

serum, blood (usually for TDM; if kidney failure and cant produce urine we may want to use this)

gastric (more important what’s absorbed, not what throwing up)
hair
meconium
sweat
oral fluid
umb cord tissue and blood
placenta

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2
Q

why is urine preferred for tox screen?

A
  • conctn of drugs higher than in blood/serum
  • easy to collect in sufficient volumes
  • metabolite detection
  • screening assay compatibility
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3
Q

urine limitations

A

no relationship between detected and..
- actual ingestion time
- amount ingested
- frequency of use/abuse
- degree of impairment
- determining conctn does NOT overcome these limitations

difficult drugs = methylphenidate (Ritalin), oral hypoglycemics

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4
Q

amphetamin general retention time

A

up to 4 days

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5
Q

MDMA/ecstasy general retention time

A

up to 4 days

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6
Q

marijuana metabolite general retention time

A

up to 30 days (chronic vs occasional)

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7
Q

cocaine metabolite general retention time

A

up to 4 days

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8
Q

opiates general retention time

A

up to 3 days

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9
Q

heroin metabolite general retention time

A

less than 1 day

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10
Q

barbiturates general retention time

A

days to weeks

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11
Q

benzodiazepines general retention time

A

days to weeks

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12
Q

methadone general retention time

A

up to three weeks

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13
Q

general retention time of alcohol

A

less than 1 day

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14
Q

immunoassay for clinical drug testing

A

initial testing

antibody-antigen rxns

refers to instrument based and non-instrument based techniques (POCT)

designed to detect broad class of drugs

limited in scope (limited assays)

cross-reactivity (ability to detect drug) dependent on reagent chemistry and devices used

prone to false negs and false pos

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15
Q

main advantage of immunoassay

A

relatively fast

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16
Q

main disadvantages of immunoassay

A

no immunoassay is absolute

it can be 100% right or 100% wrong

due to the false pos and false negs it may not be an accurate reflection of drug use

17
Q

KIMS

A

kinetic interaction of microparticles in solution

18
Q

principle of KIMS

A

competitive homogenous immunoassay

19
Q

components of KIMS

A

R1: drug derivatives conjugated to aminodextran

R2: microparticles covalently coated with Ab

20
Q

enzyme multiplied immunoassay technique

A

EMIT

21
Q

what are false negatives of immunoassays due to?

A
  • cut-offs are subjective (based on employment ‘rules’)
  • assay too specific (cocaine metabolite)
  • variance in antibody cross-reactivity within a drug class:
    > amphetamines
    > opiate: semi-synthetics
    > benzos: glucuronide metabolites (lorazepam, temazepam)
22
Q

confirmatory testing main advantase

A

definitive

23
Q

main disadvantage of confirmatory testing

A

more resource driven compared to immunoassay

24
Q

STAT tox testing

A
  • not recommended
  • quality tox testing is rarely of any valye in emergency situations for several reasons
    > does not confirm/rule out significant poisoning
    > almost never provides info that leads to a meaningful change in acute medical management
    > countless drugs contribute to common clinical symptoms seen in emerge that are not tested for immunoassay screening
    > testing not specific
    > pos test does not mean that it’s what’s contributing to pt’s symptoms
  • provincial initiative
25
Q

T or F. We use clinical tox testing for drug-facilitated assault

A

F! use for CLINICAL management of patients only
- not for employment-related purposes, insurance purposes, drug-fac assault, accident investigation/impaired driving, apprehending children under child and family services authority, etc.

cannot be used as a measurement of impairment and determining compliance is challenging!

26
Q

Benzodiazepines (KIMS)

A
  • tends to be fairly specific
  • some benzos more detectable than others
  • metabolite cross-reactivity can be poor
  • Oxaprozin or Daypro can cause false pos
  • cross-reactivity table
27
Q

these benzos are not picked dup well by the KIMS assay

A

Lorazepam glucuronide (> 20 000)
Temazepam glucuronide (> 20 000)

28
Q

GC/MS or LC/MS/MS Testing for drugs

A
  • more resource driven than immunoassay
  • gives a fingerprint of drug based on retention time and fragmentation pattern
  • identify specific compounds
  • considered confirmation tests
  • poor extraction, poor chromatographic properties of some drugs limit detection
29
Q

baseline integrity testing

A

temp

30
Q

testing for adulterants

A

pH
nitrites
hexavalent chromium
surfactants, etc.

31
Q

testing for substitution

A

creatinine
specific gravity

32
Q

hydrocodone

A

not a metabolite of oxycodone
rather a physical impurity

MLSCI 466 (19 decks)

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