Questions aléatoires SYLC Flashcards
The “hook effect” is a type of interference that primarily affects the following types of immunoassays?
A. nephelometric/turbidometric
B. competitive & immunometric
C. competitive & homogeneous
D. homogenous & heterogenous
Correct answer A.
The hook effect is decreased apparent analyte concentration at very high concentrations because of the antigen excess saturating antibody binding sites, is seen primarily in nephelometric, turbidometric, and immunometric assays. However in immunometric assays, the hook effect only occurs if there is no wash step before adding the second antibody.
Hook effect affects sandwich assays by saturating the capture antibody sites and label antibody sites preventing a sandwich formation from occurring if done in only one step. Knowing this rules out B and C as competitive assays should not be affected. A heterogenous assays having a washing step also prevents saturation of the labeling antibody which is added later after excess analyte is removed.
An important renal response to acidemia is . . .
A - increased potassium excretion.
B - increased production of ammonia.
C - decreased excretion of H2PO−4.
D - increased production of HPO42−.
The answer is B increased production of ammonia
The kidney cannot excrete significant quantities of free hydrogen ion. The most important renal response to academia is to increase the production of ammonia from glutamine. Ammonia combines with H+ in the renal tubule, and NH4− is excreted.
α-Thalassemia minor includes which of the following characteristic laboratory findings?
A. microcytosis, increased red cell number, normal red cell distribution width (RDW), and increased ferritin levels
B. microcytosis, normal red cell number, normal RDW, and decreased ferritin levels
C. microcytosis, decreased red cell number, normal RDW and increased ferritin levels
D. microcytosis, increased red cell number, elevated RDW and increased ferritin levels
E. microcytosis, decreased red cell number, elevated RDW and decreased ferritin levels
Answer : A
What is the osmolal gap, given the following data?
Freezing point depression = −0.6324 °C
Glucose = 95 mg/dL
Na = 138 mmol/L
Urea nitrogen = 28 mg/dL
A. 9 mOsm
B. 19 mOsm
C. 29 mOsm
D. 39 mOsm
E. 49 mOsm
E
One osmole of solute decreases the freezing point by 0.00186 degrees Celsius; therefore 0.6324/0.00186 = 340 mOsm/kg (measured). Calculated osmolality = (2Na) + (glucose/18) + (urea nitrogen/2.8); which comes out to 291 mOsm/Kg. Gap therefore equals 49 mOsm.
A patient seen in the clinic has a blood specimen drawn for cholesterol analysis; the results are cholesterol = 225 mg/dL, high-density lipoproteins (HDL) = 74 mg/dL, and triglycerides = 188 mg/dL. What is the indirect LDL value for this patient?
A - 37 mg/dL
B - 151 mg/dL
C - 187 mg/dL
D - 70 mg/dL
E - 113 mg/dL
Correct answer is 113 mg/dL.
Friedewald equation: LDL = total cholesterol − HDL − (triglycerides/5)
LDL = 225 mg/dL − 74 mg/dL − (188/5) mg/dL
= 113 mg/dL
Which of the following is the best method to use for determining whether a positive opiate urine drug screen is a result of poppy seed consumption?
A. testing for morphine by GC/MS in the same sample
B. testing for diacetylmorphine by GC/MS in the same sample
C. testing for monoacetyl morphine by GC/MS in the same sample
D. having patients discontinue ingesting poppy seed products and observe opiate EIAs reverting to negative levels in 48 h
E. testing for poppy seed byproducts in the urine
Answer: C
Poppy seeds contain morphine and codeine; therefore, patients consuming poppy seeds and heroin will test positive for opiates in general and specifically for morphine. However, only patients abusing heroin will test positive for 6-monoacetylmorphine, since it can only be produced from heroin.
Which of the following may raise the set point in the parathyroid gland for negative feedback, eliciting hypercalcemia?
A. Vitamin D deficiency
B. Hypomagnesemia
C. Chronic lithium therapy
D. Acute pancreatitis
E. Renal Disease
C. Chronic lithium therapy
A 38-year-old male with chronic back pain is prescribed 10-mg oxycodone tablets up to seven times per day. The results of a urine opioid confirmatory test showed codeine (973 ng/mL), hydrocodone (582 ng/mL), hydromorphone (94 ng/mL), and morphine (1300 ng/mL). The results from this test indicate that the patient is most likely taking which of the following?
A. oxycodone and codeine
B. morphine only
C. morphine and hydrocodone
D. codeine and morphine
E. codeine, hydrocodone, and morphine
E. codeine, hydrocodone, and morphine
Identify the correct statement regarding the use of population-based reference intervals based on the central 95% of the reference distribution.
A. Population-based reference intervals result in more false negatives than decision levels based on outcomes.
B. Population-based reference intervals result in more false positives than decision levels based on outcomes.
C. Population-based reference intervals are more sensitive than subject-based reference intervals.
D. Approximately 20% of comprehensive metabolic panels (14 tests) will have one or more abnormal results when performed on healthy individuals.
E. The probability of normal result(s) = (0.95)N , where N = number of tests performed.
E. The probability of normal result(s) = (0.95)N , where N = number of tests performed.
Using the bicarbonate-carbonic acid buffer system, if the apparent pKa value is 6.1 and the ratio of bicarbonate to carbonic acid is 10:1, what is the pH of the solution?
- 6.1
- 7.1
- 7.4
- 7.5
- 7.7
Correct answer : 7.1
Henderson-Hasselbalch equation:
pH = pKa + log ([A−]/[HA])
pKa = 6.1; [A−]/[HA] = 10
pH = 6.1 + log 10 = 7.1
Elevated NT-proBNP levels in pleural fluid are seen in which of the following?
A. tuberculous effusions
B. transudative effusions due to heart failure
C. transudative effusions due to liver cirrhosis
D. rheumatoid arthritis
E. empyema
B. transudative effusions due to heart failure
LDL-cholesterol can be measured directly by first removing non-LDL lipoproteins (i.e., VLDL, IDL, and HDL). The direct measurement makes use of antibodies specific to two apoproteins on non-LDL lipoproteins. What is one apoprotein that would likely be targeted by the antibody?
A. apo B-100
B. apo C-II
C. apo E
D. apo B-48
E. apo (a)
E. apo (a)
Which of the following vitamins would be LEAST affected by long periods of fat malabsorption?
- vitamin A
- vitamin C
- vitamin D
- vitamin E
- vitamin K
Correct answer: Vitamin C
Vitamins A, D, E, K are all fat soluble.
How does multiple myeloma (MM) differ from Waldenström macroglobulinemia (WM)?
A. fewer lytic lesions and less bone pain with MM
B. lower incidence of serum hyperviscosity in MM
C. fewer recurrent bacterial infections with MM
D. higher incidence of monoclonal IgM in MM
E. more visual disturbances occur with MM
How does multiple myeloma (MM) differ from Waldenström macroglobulinemia (WM)?
A. fewer lytic lesions and less bone pain with MM
B. lower incidence of serum hyperviscosity in MM
C. fewer recurrent bacterial infections with MM
D. higher incidence of monoclonal IgM in MM
E. more visual disturbances occur with MM
Wilson’s disease is a genetic disorder characterized by hepatocellular damage and/or a change in mood and behavior caused by the accumulation of which metal?
a) copper
b) iron
c) chromium
d) cobalt
e) selenium
Wilson’s disease is a genetic disorder characterized by hepatocellular damage and/or a change in mood and behavior caused by the accumulation of which metal?
- *a) copper**
b) iron
c) chromium
d) cobalt
e) selenium
The presentation of copper (Cu) toxicosis is represented by Wilson’s disease. Serum and urine copper concentrations can be useful in diagnosing Wilson’s disease. The majority of Cu circulating in blood is bound to ceruloplasmin. However, ceruloplasmin expression is decreased in Wilson’s disease. As a result, serum Cu concentrations are less than the reference interval (0.7–1.4 μg/mL), while urinary concentrations are increased to 15–60 μg/mL in patients with Wilson’s disease.
Maple syrup urine disease (MSUD) is characterized by sweet smelling urine, which is caused by which of the following?
- branched-chain amino acids excreted in urine
- glucosuria
- phenylketonuria
- no one knows
- elevated, isolated urinary excretion of alloisoleucine
Maple syrup urine disease (MSUD) is characterized by sweet smelling urine, which is caused by which of the following?
- branched-chain amino acids excreted in urine
- glucosuria
- phenylketonuria
- no one knows
- elevated, isolated urinary excretion of alloisoleucine
MUSD is a genetic disorder results in a defect in the enzyme responsible in de-branching/digesting certain amino acids. The accumulation of these amino acids and there excretion into urine gives the urine a sweet smell.
An increase in the affinity of hemoglobin for O2 can be caused by which of the following?
A. Decrease in H+ concentration
B. Increase in temperature
C. Increase in CO2 pressure
D. Increase in 2,3-diphosphoglycerate concentration
E. Decrease in Na+ concentration
An increase in the affinity of hemoglobin for O2 can be caused by which of the following?
A. Decrease in H+ concentration
B. Increase in temperature
C. Increase in CO2 pressure
D. Increase in 2,3-diphosphoglycerate concentration
E. Decrease in Na+ concentration
An 18 yo female presents to the emergency department with nausea, vomiting, fatigue, decreased appetite and a 20-lb weight loss. Blood is drawn for analysis, and her results reveal low sodium (115 mmol/L) and cortisol (188 nmol/L) and very high ACTH (912 ng/L). Additional cortisol testing was performed following a 1-h cosyntropin stimulation test with 250 μg, and cortisol remained low.
Which one of the following conditions is most likely present in this patient?
A. Cushing disease
B. Cushing syndrome
C. primary adrenal insufficiency (Addison’s disease)
D. secondary adrenal insufficiency
E. ACTH-secreting tumor
A. Cushing disease –> this is incorrect because patients typically gain weight, have high cortisol
B. Cushing syndrome –> similar to above; only the source of excess ACTH is ectopic, rather than pituitary and we would observe an increase in circulating cortisol
C. Addison’s disease –> fatigue, weakness, hyponatremia, vomiting, weight loss are typical presentation. ACTH stimulation does not induce increase in cortisol.
D. Secondary adrenal insufficiency–> incorrect, because low ACTH would be observed
E. ACTH-secreting tumor–> see A and B
A 23-y-old female presents to the emergency department with an intrauterine pregnancy at 27 weeks 3 days gestation. The patient complains of abdominal pain, contractions, and mild vaginal spotting for the past 24 h. The patient has a history of chlamydia (3 months ago) and three previous preterm deliveries. Cervicovaginal fetal fibronectin (fFN) testing was negative. How should this patient be treated?
A. Give the patient antenatal corticosteroids to induce fetal lung maturity.
B. Admit the patient and treat with a tocolytic agent, like terbutaline.
C. Discharge the patient with recommendation of pelvic rest and follow up in 1 to 2 weeks.
D. Induce delivery immediately.
E. fFN testing is inaccurate in the presence of a chlamydia infection.
The correct answer is C. The strength of fFN is its high negative predictive value, >99% for predicting birth within 7 days of sampling. Therefore, a symptomatic patient with a negative fFN result has <1% chance of delivering within the next week and can be sent home.
A lecithin-sphingomyelin (L/S) ratio is typically performed to diagnose which of the following?
a. bacterial meningitis
b. viral meningitis
c. cystic fibrosis
d. fetal lung maturity
e. multiple sclerosis
A lecithin-sphingomyelin (L/S) ratio is typically performed to diagnose which of the following?
a. bacterial meningitis
b. viral meningitis
c. cystic fibrosis
d. fetal lung maturity (très rare maintenant comme test)
e. multiple sclerosis
A blood specimen from a normal control is drawn into a citrated tube and is mixed in vitro with powdered Coumadin (warfarin). Which of the following effects would one expect to see?
A. Prolonged PT
B. Prolonged aPTT
C. Prolonged thrombin time (TT)
D. False-positive heparin assay
E. No effect
A blood specimen from a normal control is drawn into a citrated tube and is mixed in vitro with powdered Coumadin (warfarin). Which of the following effects would one expect to see?
A. Prolonged PT
B. Prolonged aPTT
C. Prolonged thrombin time (TT)
D. False-positive heparin assay
E. No effect
Coumadin or warfarin has no effect in vitro. Its action is on the vitamin K-dependent posttranslational modification of clotting factors by the liver. On the other hand, heparin will prolong the PTT and TT in vitro, and at very high doses, the PT will prolong as well.
Which of the following tube types should be specifically avoided when performing PCR-based tests?
A. EDTA
B. sodium citrate
C. lithium heparin
D. serum separator
Which of the following tube types should be specifically avoided when performing PCR-based tests?
A. EDTA
B. sodium citrate
C. lithium heparin
D. serum separator
Heparin inhibits Taq polymerase, it is a general DNA binding protein. Sodium heparin has also been known to inhibit DNA polymerase activity in PCR assays.
Which measurement is consistent with anovulation?
- High FSH on cycle day 3
- Low progesterone on cycle day 21
- High LH on cycle day 14
- Low estradiol on cycle day 3
- Low LH on cycle day 21
Which measurement is consistent with anovulation?
- High FSH on cycle day 3
- Low progesterone on cycle day 21
- High LH on cycle day 14
- Low estradiol on cycle day 3
- Low LH on cycle day 21
Following ovulation, which occurs on or near cycle day 14, the ruptured follicle gives rise to the corpus luteum, which produces estrogen and progesterone. Low concentrations of progesterone during the luteal phase indicate that ovulation has not occurred.
Which of the following quality control (QC) options best describes the traditional approach to satisfying the CLIA QC requirement?
A. assaying one level of QC twice per day
B. assaying two levels of QC once per day
C. assaying two levels of QC twice per day
D. assaying three levels of QC once per day
E. assaying three levels of QC twice per day
Which of the following quality control (QC) options best describes the traditional approach to satisfying the CLIA QC requirement?
A. assaying one level of QC twice per day
B. assaying two levels of QC once per day
C. assaying two levels of QC twice per day
D. assaying three levels of QC once per day
E. assaying three levels of QC twice per day
At a minimum, for quantitative testing, laboratories must analyze two levels of QC at different concentrations once each day of patient testing.