Cobas 8000 P2 Flashcards
TRUE or FALSE: A QC result is considered acceptable if one level of QC result is within the +/- 2 SD and the second level of QC result is outside the +/- 2 SD range and within the +/- 3 SD.
TRUE
TRUE or FALSE: A good quality control program in the clinical chemistry laboratory can measure the reliability of every result generated by the laboratory.
FALSE
A quality control program evaluates the _____ of an assay.
a. expense
b. precision
c. reference range
d. reliability
b. precision
What are the three detergent solutions used on the Cobas 8000 from the instrument manual and their function?
- Cell Clean 1: basic wash used as a probe wash when clots are sampled
- Cell Clean 2: acid wash used as a probe wash when clots are sampled
- Ectotergent: used once a day in the bath exchange, it is a surfactant and antimicrobial
What is meant by “Therapeutic Drug Monitoring”?
detection and monitoring of drugs used for disease therapy, allowing proper administration of drugs with or without toxic levels
What is meant by the terms “valley” and “peak” when dealing with aminoglycosides?
- valley/trough: drawing the blood specimen just before a dose, ensures that the patient is not at a toxic level before giving another dose of the medication
- peak: drawing of the blood specimens approximately a half an hour after a dose
Why are therapeutic drug monitoring samples often requested in this manner?
because the drugs administered are highly toxic if at high levels in the body; toxic levels can be destructive to the liver and kidneys
What are common reasons for sub-therapeutic and toxic drug levels in patients?
- patient non-compliance
- metabolism
- drug taken with/without food
- drug interaction
What are the factors that influence drug disposition in humans?
- absorption of drug
- distribution of drugs
- biotransformation of drugs
- excretion of drugs
What is lithium? What is the principle reason lithium is given to a patient?
- lithium is a mood stabilizer for manic phase-depressive disorder
- reduces extreme behavior changes
What reason, pertaining to the patient, is lithium analyzed?
lithium at critical levels is very toxic to the liver; the levels are tested to be sure the patient is at the right therapeutic level, to determine if the dosage needs to be adjusted
What is the use of the drug Lamotrigine (Lamictal)?
- an anticonvulsant agent that is used for patients whose response to the more established anticonvulsants is less than optimal
- is utilized as adjunctive treatment for partial seizures in adults
What are the side effects of Lamotrigine (Lamictal)?
- ataxia
- CNS depression
- diplopia
- dizziness
- abnormal thinking
- nausea
- nervousness
- rash
- somnolence
What is theophylline used for and their classifications?
- classification: anti-asmahatic
- uses: bronchodilator
- specimen type: serum, plasma (Na/Li Heparin)
What is phenytoin/dilantin used for and their classifications?
- classification: anticonvulsant
- uses: epilepsy, myoclonus
- specimen type: serum - no gel
What is phenobarbital used for and their classifications?
- classification: anticonvulsant/barbiturate
- uses: epilepsy, myoclonus
- specimen type: serum, plasma (Na/Li Heparin)
What is gentamicin used for and their classifications?
- classification: aminoglycoside or antibiotic
- specimen type: serum, plasma (Na/Li Heparin or Na-EDTA)
What is tobramycin used for and their classifications?
- classification: aminoglycoside/antibiotic
- specimen type: serum, plasma (Na/Li Heparin)
What is vancomycin used for and their classifications?
- classification: aminoglycoside or antibiotic
- specimen type: serum, plasma (K2-EDTA, Li Heparin)
What is digoxin used for and their classifications?
- classification: cardio-glycoside
- uses: treatment of CHF and Afib
- specimen type: serum, plasma (K2-EDTA, Li Heparin)
What is procainamide used for and their classifications?
- classification: antiarrhythmic
- specimen type: serum - no gel, plasma (Na Heparin, no gel)
What is carbamazepine used for and their classifications?
- classification: anticonvulsant
- uses: epilepsy, bipolar disorder
- specimen type: serum - no gel
What is valproic acid used for and their classifications?
- classification: anticonvulsant
- uses: epilepsy, myoclonus
- specimen type: serum, plasma (Na/Li Heparin)
What is lamotrigine used for and their classifications?
- classification: anticonvulsant
- uses: epilepsy
- specimen type: serum or non-gel heparinized plasma
What are the possible reasons that a calibration may be needed on the Cobas 8000 for the TDM’s?
- QC is unacceptable
- new lot number of reagents
- after major maintenance
What is phenytoin used for?
an anticonvulsant drug used for seizure control
What is the drug Keppra (Levetiracetam)?
- drug that is used to treat certain seizure disorders
- prescribed as an adjunctive (secondary) treatment in combination with other antiepileptic drugs
- prescribed to help prevent specific types of recurrent seizures
- one of several newer second generation antiepileptic drugs
What are the benefits of Keppra (Levetiracetam) versus the first-generation seizure medications?
- has a wider therapeutic range than many existing first generation seizure medication
- range of concentration in the blood in which the drug is effective without being toxic is broader, making it somewhat safer
- also associated with fewer side effects and does not interact with as many other drugs
What conditions may alter the binding of phenytoin to plasma proteins?
- uremia
- hypoalbuminemia
- ingestion of other drugs
- age
Why is the filtration procedure necessary when performing a free phenytoin?
removes all protein bound phenytoin to test only the active free phenytoin in patient sample
What common drug in excessive amounts causes salicylate poisoning?
aspirin
What are the side effects from overdose of salicylate?
metabolic acidosis, with high anion gap, renal failure
Acetaminophen is toxic to the ___ (organ).
liver
Why are blood lactate levels drawn in gray top tubes kept on ice and analyzed quickly?
glycolysis can rapidly increase lactate levels and putting it on ice stops metabolism
What clinical conditions have the lactic acid level increased in CSF?
- bacterial meningitis
- hypocapnia
- hydrocephalus
- brain abscesses
- cerebral ischemia
What clinical conditions have lactic acid levels increased in serum?
- shock
- pneumonia
- cardiac heart failure
- renal failure
- leukemia
What is the proper specimen collection and handling requirements when testing samples for ammonia levels?
- specimen must be collected in an EDTA tube and must be filled completely
- tube must be kept stoppered until the testing is performed
What is the principle source of blood ammonia?
gastrointestinal tract
What clinical conditions in infants and adults present with an elevated ammonia level?
- infants: Reye’s Syndrome, cirrhosis
- adults: liver failure
What is the clinical application of measuring blood alcohol level?
look for intoxication and poisoning
What is the proper specimen collection and handling requirements when testing samples for alcohol levels?
- serum is the specimen of choice
- acceptable alternatives: heparin (Li, Na, NH4), plasma
- do not use alcohol to clean the venipuncture site
- do not expose specimen to air
What is the clinical use of HbA1c test?
to ensure hemoglobinopathies or uremia on diabetes
What is proBNP? What is it used for?
- cardiac marker
- used for the diagnosis and severity of congestive heart failure
What are the acceptable specimens for the proBNP assay?
serum or heparin plasma
What kind of mechanism is demonstrated in the proBNP assay?
sandwich
What is CHF? What are some of its causes?
- cardiac heart failure: ineffective pumping of oxygen-rich blood to meet the body’s needs
- leads to accumulation of fluid in the lungs
- caused by myocardial infarction, increased blood pressure, diabetes, and increased demand
Does hemolysis, icterus, or hyperlipidemia have significant effects on the proBNP assay?
The assay is not affected if
- hemolysis <1.4 g/dL
- icterus <35 mg/dL
- hyperlipidemia: triglycerides <4000 mg/dL
- biotin <30 mg/dL
What is HCG? Where is it formed?
- human chorionic gonadotropin: a glycoprotein produced in pregnancy within the developing embryo
What is the significance of HCG? What other causes besides pregnancy might have an elevated HCG?
- significantly used in the lab to detect pregnancy
- can also be elevated in males with testicular cancer
What are the CPK Isoenzymes and the areas of the body which they represent?
- CK 1 (BB): brain, also intestinal smooth muscle, prostate, placenta
- CK 2 (MB): heart
- CK 3 (MM): skeletal muscle, also heart
What is the clinical significance of elevated CK-MB Index?
myocardial infarction
What is the formula used to calculate a CK-MB Index?
(CKMB)/CK * 100
Does hemolysis, icterus, or hyperlipidemia have significant effects on the troponin assay?
- assay unaffected by icterus (bilirubin >27 mg/dL or <462 micromoles/L), hemolysis (Hb < 0.1 g/dL or 0.062 nmol/L); falsely decreased results are obtained when using samples with higher hemoglobin concentrations
- do not analyze samples that show visible signs of hemolysis
- lipemia (<1500 mg/dL)
What is troponin?
a regulatory protein in skeletal and cardiac muscle located in the myofibrils; binds to tropomyosin and functions in muscle contraction
What condition is the troponin assay useful in diagnosis? How does it differ from CK-MB?
- useful in the diagnosis of myocardial infarction
- differs from CK-MB because it is higher in concentration for a longer window of time
What is the normal and critical range for troponin?
- normal range: < 0.05 ng/mL
- critical range: > 0.1 ng/mL
After myocardial infarction, when do troponin levels begin to rise, reach a peak level, and return to normal?
- troponin subunit TnT increases in serum 4 hours after a MI and peaks within 18 hours
- remains elevated for 7-10 days after MI and is best marker for AMI
After myocardial infarction, when does the CK-MB level begin to rise, reach the peak level, and return to normal?
- CK-MB starts to rise 4-6 hours after MI, peaks 12-24 hours later and returns to normal in 48-72 hours
- useful as an early marker for MI
After myocardial infarction, when do myoglobin levels beginto rise, reach peak, and return to normal?
- increases 2-4 hours after a MI and peaks within 6-23 hours
- returns to normal in 24-36 hours
What dilution factor does the instrument use if the HCG result is >1000 mIU/mL?
100
What type of anemia is caused by folate deficiency?
macrocytic/normochromic
What is the principle of the photometric measuring system used by the Cobas 8000?
the photometric measuring system detects color or turbidity change produced by chemical reactions between reagents and the analyte in the sample while in a reaction cell
What is the difference between endpoint spectrophotometry and rate (kinetic) spectrophotometry?
- endpoint: measures the concentration of the analyte at the end of the enzymatic reaction
- rate (kinetic): measures analyte concentration as the enzymatic reaction proceeds
What is the principle of the immunoturbidimetric assay?
- anti-analyte antibodies react with the antigen in the sample to form antigen/antibody complexes which, following agglutination, can be measured turbidimetrically
- turbidimetry measures the amount of light a solution absorbs
- absorbance is directly proportional to the concentration of the analyte in the serum
What is the principle of the homogenous particle-enhanced turbidimetric immunoassay?
- based on competition between drug in the sample and drug coated onto a microparticle for antibody binding sites of the gentamicin antibody reagent
- gentamicin coated microparticle reagent is rapidly agglutinated in the presence of the anti-gentamicin antibody reagent and in the absence of any competing drug in the sample
- rate of absorbance change is measured photometrically
- when a sample containing gentamicin is added, the agglutination reaction is partially inhibited, slowing down the rate of absorbance change
- a concentration-dependent classic agglutination inhibition curve can be obtained with maximum rate of agglutination at the lowest gentamicin concentration and the lowest agglutination rate at the highest gentamicin concentration
What is the principle of homogenous enzyme immunoassay (CEDIA)?
- based on competition between drug in the specimen and lamotrigine labeled with the enzyme glucose-6-phosphate dehydrogenase (G6PDH) for binding to the antibody reagent
- as the latter binds antibody, enzyme activity decreases
- in the presence of drug from the specimen, enzyme activity increases and is directly proportional to the drug concentration
- active enzyme converts the coenzyme nicotinamide adenine dinucleotide (NAD) to NADH that is measured spectrophotometrically as a rate of change in absorbance
- endogenous serum G6PDH does not interfere with the results because the coenzyme NAD functions only with the bacterial enzyme used in the assay
What is the principle of CEDIA (cloned enzyme donor immunoassay)?
- the bacterial enzyme B-galactosidase is cleaved into two inactive fragments
- fragments will spontaneously reassociate to form the fully active enzyme, producing a color change that can be measured spectrophotometrically
- once an inactive fragment is free in solution and the other is conjugated to the analyte on the inactive fragment, which prevents association of the fragments in solution, and active enzyme is not formed
- the amount of active enzyme formed and the resulting absorbance change is directly proportional to the concentration of analyte in the serum
What is the principle of KIMS (kinetic interaction of microparticles in solution)?
- antibody to the test drug is covalently coupled to microparticles and the drug derivative is linked to a macromolecule
- kinetic interaction of microparticles in solution is induced by binding of drug conjugate to the antibody on the microparticles, which causes lattice formation and an increase in absorbance
- when test drug is present in the sample, lattice formation is inhibited and absorbance decreases
- a competitive reaction takes place between the drug conjugate and the test drug in the serum sample for binding to the test drug antibody on the microparticles
- the absorbance resulting from kinetic interaction of microparticles is indirectly proportional to the amount of test drug present in the sample
What is the principle of ISE (ion selective electrode)?
- electrode has a selective membrane in contact with both the test solution and internal filling solution
- the internal filling solution contains the test ion at a fixed concentration
- the membrane EMF is determined by the difference in concentration of the test ion in the test solution and the internal filling solution
- electronic circuits measure and process the EMF to give the test ion concentration
- sodium and potassium electrodes are based on neutral carriers and the chloride electrode is based on an ion exchanger
What is the principle of fluorescence polarization?
- when a fluorescent molecule or fluorophore, is irradiated with light of the proper wavelength (the excitation wavelength) some of the light is absorbed
- within a few nanoseconds on the absorbed light is emitted, although at a longer wavelength (the emission wavelength)
- whether or not the emitted light is polarized depends on the freedom of the fluorophore to rotate in solution
- a small molecule, such as fluorescein, can rotate rapidly before light emission occurs, resulting in depolarization of the emitted light
- in contrast, a fluorescent macromolecule, such as fluorescein-labeled protein, will rotate much more slowly
- thus, in the time frame between excitation and emission, the macromolecule will have rotated only very slightly and the emitted light will be polarized
- fluorescence polarization is a reproducible function of the drug concentration, and is suitable for the quantitative determination of drug concentrations in serum for the purpose of therapeutic drug monitoring
What is the measuring range for digoxin?
0.15-5.0 ug/mL
What is the measuring range for theophylline?
0.8-40.0 ug/mL
What is the measuring range for carbamazepine?
0.5-20 ug/mL
What is the measuring range for phenytoin?
0.8-40.0 ug/mL
What diluent would you use to dilute the specimen, if the concentration of the therapeutic drug is higher than the measurement range?
- digoxin: x2 dilution with universal diluent; >5.0 ug/mL
- theophylline: x2 dilution is performed with TDM1 DIL; >40 ug/mL
- phenytoin: x2 dilution is performed with TDM1 DIL; >40 ug/mL
- carbamazepine: core TDM multi-cal low calibrator is used; >20 ug/mL
