Chemistry Set 2
Bioavailability of an oral drug refers to the:
Availability for therapeutic administration Ratio of protein-bound to free drug Amount of drug transformation Fraction of the drug that is absorbed into systemic circulation
A patient has a fasting plasma glucose (FPG) performed at an outpatient laboratory. He has fasted as instructed. FPG: 135 mg/dL What does this result indicate and what, if any, further action is recommended by the ADA?
Elevated FPG; needs further evaluation by a repeat or alternative test Decreased FPG; a repeat of the test is recommended in one year Sufficient documentation for diagnosis of diabetes Needs no further evaluation; this is a normal FPG
When three tubes of cerebrospinal fluid are received in the laboratory they should be distributed to the various laboratory sections as follows:
#1 Hematology, #2 Chemistry, #3 Microbiology #1 Chemistry, #2 Microbiology, #3 Hematology #1 Microbiology, #2 Hematology, #3 Chemistry #1 Chemistry, #2 Hematology, #3 Microbiology
Which of the following proteins has the fastest electrophoretic mobility?
Albumin Alpha globulins Beta globulins Gamma globulins
All of the following have an impact on electrophoresis techniques in the clinical lab EXCEPT?
Amount of light present in electrophoresis box Support medium pH Voltage
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Free ionized calcium is important in physiologic functions such as coagulation and neuromuscular conductivity. Bound calcium is not biologically active. About 45% of Ca2+ circulates as free ionized calcium, 40% is bound to protein and about 15% is bound to anions (HCO3-, citrate, and lactate).
A patient suffering from Celiac disease and Crohn disease (both inflammatory conditions of the GI tract) is given a new oral medication that has a narrow therapeutic window. Which of the following would be true?
An oral medication is never effective for a patient that has these diseases. The drug must be given through IV. Toxicity in this patient is not likely since most of the drug won't be absorbed. Therapeutic drug monitoring (TDM) would be helpful to see how much drug has been absorbed. Serum drug levels obtained 15 minutes after the oral dose should confirm the drug was absorbed.
A 45-year-old African American female has been diagnosed and treated for type 2 diabetes for the past five years. She maintains good control of her blood glucose with medication but does not exercise and has gained 12 pounds over the past year. At her next appointment, her physician orders hs-CRP along with blood assays to monitor her diabetes. Laboratory Result: hs-CRP 2.8 mg/L
At no risk for cardiovascular disease Low risk for cardiovascular disease Moderate risk for cardiovascular disease High risk for cardiovascular disease
Which of the following lipid tests is LEAST affected by the fasting status of the patient?
Cholesterol Triglycerides Fatty acids Lipoproteins
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Cholesterol levels do not fluctuate as triglycerides, fatty acids, lipoproteins, and chylomicrons do after an individual eats a meal. This is the reason that patients are told to fast; the laboratory needs a fasting sample to determine a lipid profile or panel which includes the latter four components.
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Either protein electrophoresis or immunoelectrophoresis can be used to confirm Bence-Jones proteinuria. Benedict test is used for detecting glycosuria. The Ictotest is used for detecting urine bilirubin. Watson-Schwarz test is used in the detection of porphobilinogen and urobilinogen.
Total iron-binding capacity measures the serum iron transporting capacity of:
Hemoglobin Transferrin Ferritin Ceruloplasmin Haptoglobin
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In 2003 the American Heart Association and the CDC published a set of clinical guidelines for the use of hs-CPR as a marker for carviovascular disease (CVD) risk. hs-CRP <1 mg/L represents low risk of CVD hs-CRP 1.0-3.0 mg/L represents moderate risk of CVD hs-CRP >3.0 represents high risk of CVD In our case, a hs-CRP of 2.8 mg/L indicates a moderate risk of CVD (1.0-3.0 mg/L).
Metabolic acidosis is characterized by:
Increased pCO2 Hypoventilation Low pH High pH
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Magnesium is the 4th most abundant caition in the body, but is not included in the electrolyte panel testing. The electrolyte panel consists of potassium (K+), sodium (Na+), chloride (Cl-), carbon dioxide (in form of bicarbonate HCO3-). These analytes are also typically ordered within other panels as well, including the basic metabolic and complete metabolic panels. Electrolites are charged particles (ions) whose function is the maintanance of water homeostasis, acid-base balance, muscle function, as well as serving as cofactors for enzymes. Those negatively charged electrolytes are called anions (Cl-, HCO3-) and those positively charged are called cations (K+, Na+). An imbalance in electrolytes is extremly harmful to the patient and can be fatal.
Most common methods for measuring bilirubin are based on the reaction of bilirubin with:
Methyl alcohol Neural salts Bilirubin oxidase Diazo reagent
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The bioavailability of an oral drug is the fraction of the drug that is absorbed into systemic circulation. The bioavailability of a drug is calculated by comparing the area under the plasma concentration-time curve of an equivalent dose of the intravenous form and the oral form of the drug. For oral drugs to be effective, bioavailability typically should be greater than 70%.
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The pH of this patient sample is alkaline (>7.45), which is indicative of alkalosis. Since the HCO3- is increased (reference range 22-29 mmol/L) and is the alkaline buffer component of the body produced by our metabolic system, the condition is called metabolic alkalosis.
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The pH will be normal in a fully compensated form of any alkalosis or acidosis. In this case, the problem is metabolic, meaning there is a decrease in bicarbonate (alkaline) production which has reduced the pH of the blood. To compensate for this, the patient hyperventilates thus reducing the amount of acid, or pCO2 in the system to balance the pH into normal range.
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The result is elevated. Hyperglycemia is demonstrated by this one FPG. The ADA recommends that the hyperglycemia be demonstrated a second time by repeating the FPG or by using one of the other recommended diagnostic tests. Hyperglycemia should be demonstrated a second time by any of the four criteria unless the glucose level is significantly high and diabetes is unquestionable. The four diagnostic creiteria include: HbA1c ≥6.5% FPG of ≥ 126 mg/dL An oral glucose tolerance test with a 2-hour postload (7g glucose) level of ≥200 mg/dL Random FPG level of ≥200 mg/dL and symptoms of diabetes
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The serum proteins can be separated into five fractions by serum protein electrophoresis. In order of decreasing electrophoretic mobility these fractions are the: serum albumin, alpha-1 globulins, alpha-2 globulins, beta globulins, and gamma globulins.
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The type of support media, type of stains used, and voltage settings all have an impact on electrophoresis techniques; however, the amount of light present in an electrophoresis box does not. Support medium can affect migration of analytes based on the medium's pore size and endosmosis. pH can change the charge of the analyte and thus affect the mobility. It can also denature the analyte (protein). Voltage is proportional with the velocity of the analyte migration. Ionic strenght, ions present, wattage, current, temperature, and time are other variables that can affect electrophoretic results.
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Transferrin is a glycoprotein that reversibly binds iron. Total iron binding capacity measures the amount of transferrin that is available to bind with iron in the serum. Transferrin binds iron in the serum, and is proportional to total iron-binding capacity (TIBC). Serum transferrin (mg/dL) = 0.7 X TIBC (µg/dL) Total iron-binding capacity does not measure hemoglobin, ferritin, ceruloplasmin, or haptoglobin.
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When three tubes of CSF are collected, the first tube is used for chemical and/or serological analysis. The second tube is used in microbiology in order to prevent any contamination of the bacterial culture by skin microbiological flora that may have occurred during the insertion of the spinal needle during he collection process. The last tube (#3) should always be used for hematology studies in order to minimize the effect of any peripheral blood (traumatic tap) contamination which may have occurred during the insertion of the spinal needle.
You are working in a clinical chemistry laboratory and are analyzing a plasma glucose sample. The sample is flagged by the analyzer for being "outside of linear range." You manually dilute the sample 1:2 and rerun it. Again, you receive an "outside linear range" alert. You decide to perform a different manual dilution. This time you manually dilute the original sample again; this time using a 1:3 dilution. The instrument gives you a glucose value of 150 mg/dL from this diluted sample. What is the actual patient glucose result that you should report to the physician?
100 mg/dL 400 mg/dL 600 mg/dL 450 mg/dL
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Beer's law is based on the fact that absorbance is directly proportional to the concentration of a solution. Therefore, stray light within an instrument can alter the absorbance results in this type of assay.
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Diazotized sulfanilic acid (diazo reagent) reacts with bilirubin to produce azodipyrrole, which has a red-purple color and can be measured spectrophotometrically. This reaction was first described by Ehrlich in 1883 using urine samples.
The following results were obtained on arterial blood: pH = 7.51 pCO2= 49 mm Hg HCO3- = 38.7 mmol/L pO2= 85 mm Hg These results are compatible with:
Metabolic acidosis Respiratory acidosis Metabolic alkalosis Respiratory alkalosis
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Metabolic acidosis is the result of either: 1) accumulation of abnormal levels of organic acids, often secondary to diabetic ketoacidosis, or lactic acidosis, 2) excessive loss of bicarbonate as in severe diarrhea, or 3) reduced excretion of acids as in renal failure. All these conditions result in a decrease in pH. The body compensates by hyperventilating, and lowering pCO2, in an attempt to restore normal pH, resulting in a compensated or partially compensated metabolic acidosis.
A young man is experiencing difficult breathing after fainting. The physician orders an arterial blood gas analysis which shows the following results: pH = 7.25 pCO2 = 62 mmHg pO2 = 70 mmHg HCO3- = 23 mmol/L Which condition is most likely afflicting this patient?
Metabolic alkalosis Metabolic acidosis Respiratory alkalosis Respiratory acidosis
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Myoglobin and CK-MB are present in skeletal muscle and can be elevated in injury to these cells. Other causes of increased myoglobin and CK-MB levels include: Severe injury to skeletal muscle Strenuous exercise Extremely difficult breathing (increased use of chest muscles) Kidneys failure Chronic muscle disease Alcohol abuse Troponin T and I tests are much more specific to cardiac muscle than myoglobin and CK-MB assays. CK-MB is relatively cardiospecific, but small amounts of CK-MB are also present in skelatal muscle, uterus, and prostate, therefore TnI and TnT are better for assesing myocardial damage.
Respiratory acidosis is associated with:
Normal pH High pH Decreased pCO2 Increased pCO2
Which of the following forms of calcium is biologically active:
Protein-bound calcium Non-ionized calcium Calcium carbonate *Free ionized calcium*
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Respiratory acidosis occurs when the lung's ability to remove carbon dioxide is decreased, resulting in increased blood pCO2 and acidosis.
Which of the following would NOT be considered a normal part of a routine electrolyte panel (profile)?
Sodium Potassium Magnesium Chloride
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TDM would be helpful to see how much drug has been absorbed. Blood collection for the TDM test should occur at least one hour after the administration of the oral drug. Measuring the serum level of the drug 15 minutes after the oral dose has been given is not sufficient time to allow for absorption Celiac disease and Crohn's disease are both inflammatory conditions of the GI tract that can cause decreased absorption. Although an IV drug may be preferred, not all drugs are available as IV solutions; until low absorption is confirmed, an oral drug may be tried. The patient may or may not have poor absorption, but toxicity could still occur regardless of absorption. For example, toxicity to the GI tract could ensue without the drug ever being absorbed.
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The correct response is 450 mg/dL. A 1:3 dilution entails mixing one part patient sample with two parts diluent, for a total volume of 3 parts. In laboratory dilutions, the total volume is considered a dilution factor. The dilution factor in this question is 3. So a diluted sample with a value of 150 would need to be multiplied by 3 to obtain the correct final answer. 150 x 3 = 450 mg/dL.
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Unconjugated bilirubin is a byproduct of RBC breakdown, or hemolysis. It would be expected to see an increase in unconjugated bilirubin when hemolysis is occuring at an increased rate. The liver enzymes would not remain at normal levels if there were a viral infection of the liver, chemical damage to the liver, or obstruction of bile ducts.
Which of the following methods would be used to confirm the presence of Bence-Jones protein in the urine:
Urine protein electrophoresis or immunoelectrophoresis Benedict qualitative test Ictotest Watson-Schwartz test
Deviations from Beer's Law are caused by:
Very low concentration of absorbing material Polychromatic light Very high concentrations of substance being measured in a colorimetric reaction Stray light
A patient presents with an elevation of unconjugated bilirubin, normal serum alkaline phosphatase, normal liver enzymes, and no bilirubin in the urine. This combination would suggest:
Viral infection of the liver. Chemical damage to the liver. Increased rate of hemolysis Obstruction of common bile duct
Which two of the following biomarkers are not specific to cardiac muscle and may be elevated in patients with injury to muscle other than cardiac muscle?
cTnI and cTnT CK-MB and myoglobin cTnT and CK-MB Myoglobin and cTnI
Select the statement that best describes high sensitivity CRP (hs-CRP) testing?
hs-CRP is a measurement of acute inflammation and is used to monitor these type of conditions hs-CRP is an anti-inflammatory adipokine synthesized by adipocytes *hs-CRP is a marker of chronic inflammation and measured to predict the risk of cardiovascular disease* hs-CRP is decreased in inflammatory conditions and measured to predict a return of inflammation
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hs-CRP is a newer marker of chronic inflammation. This new test measures low levels of CRP, (hs-CRP) and can therefore be used to monitor the risk of cardiovascular disease. Levels of <1 mg/L, 1to 3 mg/L, and >3mg/L correspond to low, moderate, and high risk for future cardiovascular events.
Which of the following is TRUE of a fully compensated metabolic acidosis?
pH will be decreased without a decrease in pCO2 pH will be decreased with a decrease in pCO2 pH will be decreased with an increase in pCO2 pH will be normal with a decrease in pCO2