Capstone Chemistry (70-88)

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cruz_852000
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294111
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Capstone Chemistry (70-88)
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2015-02-01 12:36:36
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clinical chemistry
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(70-88) quiz #3
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  1. What are the most widely abused drugs in the U.S.?
    Amphetamines, cocaine, cannabinoids, opiates, barbiturates, benzodiazepines, methadone, methaqualone, and phencyclidine (PCP).
  2. What are other names for marijuana?
    Cannabinoids or THC (tetrahydrocannabinol).
  3. What is the most common method for screening for drugs of abuse?
    Immunoassays such as EIA and FPIA. Confirmation of a presumptive positive is mandatory in forensic drug testing. The analytical method of choice for confirmation is gas chromatography with mass spectroscopy detection (GC/MS).
  4. How can an altered urine specimen for drug testing be detected?
    Dilution is recognized by a specific gravity less than 1.003 and a creatinine less than 20 mg/dl. Substitution is recognized when specific gravity is less than 1.001 or greater than 1.020 and creatine is less than 5 mg/dl. Adulteration is present if nitrite is greater than 500 ug/ml or if the sample contains a substance that is not normally found in urine or is found at a concentration higher than physiologic. The temperature of urine immediately following collection should be 90.5-98.9 F. Spot and strip tests are available to detect commercial adulterants that are not detected by routine specimen integrity tests.
  5. Discuss the Substance Abuse and Mental Health Services Administration's (SAMHSA) recommended protocol for collection of urine for drug testing?
    The water supply should be turned off in the collection area. Bluing should be added to the toilet water. Patients should not be permitted to take coats, purses, ect. into the collection facility.
  6. Why should serum separator tubes not be used for most therapeutic drug monitoring assays?
    Some drugs concentrations are affected by contact with some types of gel separator tubes.
  7. What is the role of the medical review officer?
    To determine the cause of positive drug test results and provide counseling.
  8. What method is most often used to preform therapeutic drug monitoring?
    Immunoassay
  9. Name the most common anticonvulsant used to control grand mal seizures.
    Phenytoin or dilantin
  10. What is the major metabolite of the anticonvulsant primidone?
    Phenobarbital. When a primidone assay is ordered, phenobarbital must also be assayed for complete result interpretation.
  11. Name a drug that relaxes the smooth muscles of the bronchial passages.
    Theophylline. It is used to treat asthmatics.
  12. What is the metabolite of theophylline?
    Caffeine.
  13. When should blood be drawn for a peak drug level?
    Upon achievement of steady state. Steady state is reached when the amount of drug absorbed and distributed is equal to the amount of drug metabolized and excreted. This usually occurs after 5-7 half-lives. The half-life of a drug is the time required for the concentration of the drug to be decreased by half. 
  14. A patient is to be given an oral dose of a drug every 8 hours. The drug has a half-life of 8 hours. After how many doses should the patient reach steady state concentration?
    5-7
  15. When should blood be drawn for a trough drug level?
    Just before the next scheduled dose.
  16. Name three anti-arrhythmias.
    Lidocaine, digoxin, and digitoxin. 
  17. Which antibiotics are monitored by therapeutic drug monitoring?
    Aminoglycosides (amikacin, gentamicin, neomycin, netilmicin, kanamycin, streptomycin, tobramycin), chloramphenicol, and vancomycin. These antibiotics have toxic effects such as nephrotoxicity and ototoxicity outside of the therapeutic range. 
  18. Which hemoglobin is elevated in a patient with carbon monoxide poisoning?
    Carboxyhemoglobin. Levels are determined on a co-oximeter. Carbon monoxide is toxic because the affinity of of hemoglobin for carbon monoxide is 200 times that of oxygen. 
  19. How is lithium measured?
    By flame photometry, ion selective electrode, or atomic absorption. Lithium is administered to treat manic-depressives. Levels must be monitored to avoid toxicity. 
  20. What are tumor markers?
    Tumor markers are constituents of health cells that are produced in large quantity by cancer cells. 
  21. How are tumor markers used clinically?
    They are used to assess the response to cancer treatment and to monitor for recurrence of the cancer. It is changes in concentration over months or years that is significant, rather than a single value. Consecutively rising levels are an indicator that the cancer has returned. Tumor markers are not used to screen for cancer because their specificity is low and there would be many false positive results. 
  22. What is the clinical significance of carcinoembyronic antigen (CEA)?
    CEA is a substance normally found in fetal tissue. It is found in the blood of patients with cancer of the colon and other types of cancer. CEA testing is not approved as a screening method for detecting cancer. Its primary application if for monitoring patients who have been treated for colorectal cancer. A steadily rising CEA level may be the first sign that the cancer has returned. CEA is measured by enzyme immunoassay. 
  23. What is alpha-fetoprotein (AFP)?
    AFP is a protein produced by the liver of the fetus that declines to adult levels by 18 months of age. It is elevated in the serum of patients with cancer of the liver, testicles, or ovaries. Maternal serum AFP is one of the tests in the maternal serum triple or quadruple screening test that is done between 16 and 18 weeks of gestation to diagnose spina bifida, anencephaly, and Down's syndrome. The other tests in the triple screen are beta-HCG and unconjugated estriol. The quad screen also measures the hormone inhibit-A
  24. What is the role of human chorionic gonadotropin (hCG) in the management of cancer?
    It is used to monitor patients with testicular cancer and gestational trophoblastic disease (e.g., molar pregnancy)
  25. What is CA-125?
    Cancer antigen (CA) 125 is an oncofetal antigen that is sometimes present with ovarian and other types of cancer. The CA-125 test is used to monitor, not to diagnose, ovarian cancer. Decreasing levels indicate that the cancer is responding to therapy. Increasing levels indicate a return or continued growth of the cancer. There are no presently no reliable screening tests for the diagnosis of ovarian cancer.
  26. What are CA 15-3 and CA 27.29?
    They are cancer antigens that are used to monitor therapy in patients with breast cancer and to evaluate for cancer recurrence.
  27. What is the clinical utility of CA 19-9?
    In patients with pancreatic cancer, CA 19-9 levels correlate well with the stage of disease. CA 19-9 is a Lewis blood group antigen so it is of no utility in Lewis-negative individuals. 
  28. What is prostate-specific antigen (PSA)?
    A marker for prostate cancer. PSA is the only tumor marker approved for general screening. PSA has replaced acid phosphatase because of its increased sensitivity. 
  29. What is the clinical utility of thyroglobulin (Tg)?
    It is useful in the management of patients with thyroid cancer. Following total thyroidectomy and/or radio ablation, and in the absence of recurrent disease, Tg should be undetectable. Antithyroglobulin antibody levels should also be measured because their presence can render Tg results invalid. 
  30. What method is used for testing for tumor-associated antigens?
    Immunoassays
  31. Which methods used in clinical chemistry are photometric methods?
    Spectrophotometry, flame emission photometry, atomic absorption spectrophotometry, and fluorometry. 
  32. Is light of 340 nm is in the ultraviolet, visible, or infrared range?
    Ultraviolet. The visible range is from 400-700 nm. Infrared is from 750-2000 nm.
  33. What light source is used for work in the ultraviolet range?
    Deuterium-discharge or mercury-arc lamp
  34. What light source is used for work in the visible and near-infrared range?
    Incandescent tungsten or tungsten-iodide
  35. In a spectrophotomer, what isolates light of a specific wavelength from white light?
    The monochromator. Filters, prisms, or diffraction gratings are used. Diffraction gratings are most commonly used. 
  36. What is bandpass on a spectrophotometer?
    The width of the segment of the spectrum that will be isolated by a monochromator. The better the spectrophotometer, the narrower the bandpass. 
  37. What is the purpose of a photodetector in a spectrophotometer?
    It converts light energy into electrical energy.
  38. What is the advantage of a double beam spectrophotometer?
    It has a reference light beam and a measuring light beam. Variation in lamp intensity or detector sensitivity is compensated for by expressing the absorbance as a ratio between the reference light beam and the measuring light beam. 
  39. What is the relationship between percent transmittance (%T) and absorbance?
    A=2-log%T
  40. Why should all the cuvettes used in a series of colorimetric readings be of the same diameter?
    So that the light path through the solution is the same. 
  41. What type of cuvettes are required for UV and infrared work?
    Quartz. Borosilicate cuvettes are used in the visible range. 
  42. What is the purpose of a blank in spectrophotometry?
    It subtracts out any absorbance due to the reagents alone.
  43. According to Beer's law, what is directly proportional to concentration?
    Absorbance. 
  44. What is the main advantage of fluorometry over spectrophotometry?
    Fluorometry is much more sensitive. 
  45. In a fluorometer, how does the light emitted by the specimen differ from the light absorbed?
    The emitted light is of a longer wavelength (lower energy). 
  46. Why is the photodetector in the fluorometer placed at right angles to the light source?
    So that only light emitted from the sample is measured and not light from the light source. 
  47. What is the principle of flame emission photometry?
    A photon of light with a wavelength specific for a given element is emitted when orbital electrons excited by heat return to the ground state. Once used to measure sodium and potassium, today use of the flame photometer is limited to measuring lithium.
  48. What is the purpose of the internal standard in flame photometry?
    To minimize the effect of variations due to the rate of atomization, flame stability, viscosity of the solution, or fluctuations in gas/air flow rates. Lithium or cesium is added to all calibrators, blanks, and samples in equal concentrations. The flame photometer makes a comparison of the emission of the analyze with the emission of the internal standard. 
  49. What is the light source in atomic absorption spectrophotometry?
    A hollow cathode tube with a cathode of the material to be analyzed. Atomic absorption is used to measure trace metals. It is the reference method for calcium (but not routinely used) and is one of the recommended methods for measuring lead. 
  50. What does a nephelometer measure?
    Light scattering by antigen-antibody complexes in a solution. This method is used to measure immunoglobulins, immune complexes, complement, and other proteins such as transferrin and preablumin.
  51. What does a nephelometer measure?
    Light scattering by antigen-antibody complexes in a solution. This method is used to measure immunoglobulins, immune complexes, complement, and other proteins such as transferrin and pre albumin. 
  52. What is the difference between nephelometry and turbidimetry?
    Turbidimeters and nephelometers both measure the intensity of light scattering. Turbidity decreases the intensity of the beam of light as it passes through a solution of particles. The measurement is about 180o, just as absorbance is measured in a spectrophotometer. Turbidity can be measured on most spectrophotometers and automated chemistry analyzers. Nephelometers measure scattered light at right angles to the incident light, much like a fluorometer. Nephelometry is a more sensitive technique when measuring low-level antigen-antibody reactions. 
  53. What is the basis for separation of compounds in chromatographic procedures?
    Chromatography separates solutes based on their differential attraction to the stationary phase as they are carried through in the mobile phase. 
  54. In thin layer chromatography, what is the Rf value?
    The ratio of the distance moved by the compound to the distance moved by the solvent. 
  55. What type of substances can be analyzed by gas chromatography (GC)?
    Volatile substances or substances that can be made volatile. These compounds are identified by their retention time. Ethanol can be measured by GC.

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