An International unit (IU) of enzyme activity is the quantity of enzyme that:

Converts 1 μmol of substate to product per minute

Which enzyme statement below describes a nonkinetic enzyme assay ?

Initial absorbance is measured, followed by a second reading after 5 minutes

Which if the following statements regarding enzymatic reactions is true ?

The enzyme increases the rate  of the reaction

Which statement about enzymes is true ?

A competetitive inhibitor will alter the apparent K_{m (Michaelis-Menten Constant)} of the reaction

Which substrate concentration is needed to achieve zero-order conditions ?

> than 99 x K _m

Which statement is true ?

Apoenzyme + prosthetic group = holoenzyme

Which of the following statements about enzymatic reactions is true ?

NADH has absorbance maximum at 340 and 366 nm

The increase in the level of serum enzyme used to detect cholestatic liver disease is caused mainly by :

Increased production and secretion by cells

Which enzyme below is considered most tissue specfic ?

Alcohol dehydrogenase

(along with ALT-necrotic liver disease)

Which of the following enzymes is activated by calcium ions?

Amylase

Which of the following enzymes is a transferase ?

CK

(not - Alkp,Amy,LD)

Which statement about the methods for measuring LD is true ?

The pyruvate to lactate reaction proceeds at about twice the rate as the forward reaction

Which condition produces the highest elevation of serum lactate dehydrogenase ?

Pernicious Anemia

Which condition is the LD most likely to be within normal limits .?

Acute appendicitis

(not hepatic ca,pulmonary infarct,crush injury)

Following an acute MI, activity of LD usually peaks:

Three days postinfarction and returns to normal after 1 week.

The LD pleural fluid:serum ratio for a transudative fluid is usually :

1:2 or less

Which type of liver disease would you expect the greatest elevation of LD ?

Toxic hepatitis

(not etoh hepatitis,cirrhosis,acute viral hepatitis)

Which of the following conditions will interfere with measurement of LD ?

Slight hemolyis during sample collection 

(LD is stable 2 days at RT or 1 week in refer)

In the Oliver-Rosalki method, the reverse reaction is used to measure CK activity. The enzyme used in the coupling reactions are:

Hezokinase and G6PD

In the Oloiver-Rosalki method for CK, adenosine monophosphate(AMP) is added to the substrate in order to :

Inhibit adenylate kinase

Which substance is used in the CK assay to activate the enzyme ?

N-acetylcysteine

Specimen for CK performed on an automated analyzer gives an error flag indicating substrate depletion. The sample is diluted x2 and x4. After correction the results are as follows:

x2=3000       x4=3600    Explanation ?

An endogenous competitive inhibitor is present in the serum

2 hour old citrated coag sample, can we add on a CK?

No, citrate will interfere

Which of the statements below regarding total CK is true?

Highest levels are seen in Duchenne's Muscular Dystrophy.

Which of the following statements regarding the clinical use of CK-MB (CK-2) is true ?

Mass unit assays are more sensitive than electrophoretic methods

Isoforms of CK are:

Formed in the circulation by hydrolysis of lysine from CK-MM and CK-MB

A patient's CK-MB is reported at 18 and the total CK as 560. What is the CK relative index?

3.2%

CKI =    CK-MB     _{x 100}

Total CK

In a nonmyocardial as opposed toa myocardial cause of an increased serum or plasm CK-MB, which would be expected?

An increase in CK-MB that is persistent.

Which statement best describes the clinical utility of plasma or serum myoglobin ?

Levels below 100 on admission and 2-4 hours postadmission help to exclude a diagnosis of acute MI.

What is the typical time course for plasma myoglobin following an acute MI ?

Abnormal with in 3 hours, peaks within 12 hours, returns to normal in 36  hours.

What is the typical time course for plasma TnI or TnT following an acute MI ?

Abnormal within 4 hours, peaks within 24 hours, returns to normal in 1 week

Which of the following is the most effective serial sampling tiem for ruling out acute MI using both myoglobin and a cardiac spedific marker in an emergency department environment ?

Admission, 3 hrs, 6 hrs and a final sample within 12 hrs

Whic of the cardiac markers is consistently increased in persons who exhibit unstable angina ?

Troponin T

Patient has a myoclobin level of 10 at admission. three hours later the myoglobin is 14 and the Tropponin I is 0.04 (ref 0.0-0.4) Results are consistent with what condition ?

No evidence of myocardial or skeletal condition .

A patient has a plasma CK-MB of 14 at admission and a totla CK of 170. Myoglobin is 130 and TnI is 1.6. Three hours later the cK-MB is 24. What best descrives this situation ?

This patient has had an acute MI and further testing is unnecessary.

EDTA sample for TnI assay gives result of 0.7(ref0.0-0.4). The test is repeated three hours later and is 0.6, six hours later is 0.7. Most likely explanation ??

The patient has suffered cardiac injury, probably less severe than an MI.

Which of the following lab tests is a marker for ischemic heard disease ?

Albumin cobalt binding.

Which test provides the earliest warning of increased risk of coronary artery disease ?

High sensitivity CRP

Which statement best describes the clinical utilitity of B-type natriuretic peptide (BNP) ?

A normal test result helps rule out congestive heart failure in persons with symptoms associated with coronary insufficiency.

Which best describes the clinical utility of plasma homocysteine ?

High plasma levels are assiciated with atherosclerosis and increased risk of thrombosis.

Which of the following statements about the aminotransferases  (ALT & AST) is true ?

Both transfer an amino group to α-ketoglutarate

Select the products formed from the forward reaction of AST ?

Oxaloacetate and glutamate

Select the products formed form the forward reaction of ALT ?

Pyruvate and glutamate

Which of he statements below regarding the methods of Henry for AST and ALT is correct ?

Hemolysis causes positive interference in both AST and ALT assays

Select the coupling enzyme used in the kinetic reaction of Henry ?

Malate dehydrogenase

What is the purpose of LD in the kinetic method of Henry for AST ?

Rapidly exhausts endogenous pyruvate in the lag phase

Which statement regarding the naming of transaminases is true ?

SGPT is the old abbreviation for ALT

Which statement accurately describes serum transaminase levels in AMI ?

AST peaks 24-48 hours after an acute MI and returns to normal with 4-6 days

Which condition gives rise to the highest serum level of transaminases ?

Acute hepatitis

In which liver disease is the DeRitis ratio (ALT:AST) usually greater than 1.o ?

Acute hepatitis

(ALT prevails over AST in acute hepatitis, but AST is higher than ALT in chronic hepatitis, carcinoma and cirrhisis of the liver)

Which of the following liver diseases produces the highest levels of transaminases ?

Chronic hepatitis

Which of the following statements regarding transaminames is true ?

ALT is far more spedific for liver diseases than is AST

Select the most sensitive marker for alcoholic lever disease ?

GGT

Which enzyme is least useful in differentating necrotic from obstructive jaundice ?

LD

Which of the statements below about the phosphatases is true ?

They are divided into two classes based upon pH needed for activity (alkaline or acid)

Which of the following statements regarding ALP is true ?

Pregnant women have a higher lever of serum ALP than other adults

Which isoenzyme of ALP are inhibited by L-phenylalanine ?

Intestional and placental

Which isoenzyme of ALP is most heat-stable ?

Placental

Which isoenzyme of ALP migrates farthers toward the anode (+) when electrophoresed at pH 8.6 ?

Liver

Which isoenzyme of ALP is inhibited by urea ?

Bone

Which of the following statements regarding ALP is true ?

 Elevated serum ALP seen with elevated GGT suggests a hepatic source

In which condition would an elevated serum alkaline phosphatase be likely to occur ?

Squamous cell carcinoma

Which condition is least likely to be associated with increased serum ALP concentrations ?

Osteoporosis

Which substrate is used in the Bowers-McComb method for ALP ?

p-Nitrophenylphosphate

Which of the following buffers is used in the IFCC recommended method for ALP ?

2-amino-2-methyl-1-propanol

Serum form a 50 year old collected following digital exam. Prostatic acid phos 6.o (upper ref 3.0)

PSA 2.0 (upper ref 4.0) Most likely explanation ?

Acid phos is falsely elevated by prostatic irritation

Which definition best describes the catalytic activity of amylase  ?

Hydrolyzes second a-1-4-glycosidic linkages of starch,glycogen and other polyglucans 

Which of the following anylase methods is typically based upon a rate reaction ?

Turbidimetric

How soon following acute abdominal pain due to pancreatitis is the serum anylase level expected to rise ?

2-12 hours

Which of the statements below regarding the diagnosis of pancreatitis is correct ?

Diagnostic sensitivity is increased by assaying both amylase and lipase

Which of the following conditions is associated with a high level of S-type anylase ?

Mumps

S-salivary

Which of the statements regarding amylase methods is true ?

Amyloclastic methods measure the production of glucose.

Which of the following statements regarding amylase methods is true ?

Synthetic substrates can be conjugated to p-nitrophenol (PNP) for a kinetic assay ?

The reference method for lipase uses olive oil as the substrate because ?

Other esterases can hydrolyze triglyceride and synthetic diglycerides

Which statement about the clinical utility of plasma or serum lipase is true ?

Lipase is not incresed in mumps, malignancy or ectopic pregnancy

The reference method for serum lipase is based upon :

Titration of fatty acids with dilute NaOH following controlled incubation of serum with olive oil

The most commonly employed method of assay for plasma or serum lipase is based upon:

Peroxidase coupling

Which of the following enzymes is usually depressed in liver disease ?

Pseudocholinesterase

A serum ALP lever greater than twice the elevation of GGT suggests:

Bone disease or malignancy

How many of the substances below would be neede to enable an early diagnosis of stroke ?

D-Dimer, vonWillebrand's factor, matric metalloproteinase-9, S100B, BNP, vascular cell adhesion molecule .

All six

Which of the following  hormones is often decreased by approx 25% in the serum of pregnamt women who have a fetus with Down's Syndrome ?

EStriol (E3)

The syndrome of anapprioate antidieuretic hormone secretion (SIADH) causes:

Urine osmolality to be lower than that of plasma osmo

Select the hormone that is associated with galactorehea, pituitary adenoma, and amehorrhea ?

Prolactin

Zollinger-Ellison(Z-E) syndrome is characterized by great (20 fold) elevation of :

Gastrin

Which statement about multiple endocrine neoplasia (MEN) is true ?

It is associated with hyperplasia or neoplasia of at least two endocrine organs

Select the main estrogen produced by the ovaries and used to evaluate ovarian function ?

Estradiol (E2)

E2 is the major estrogen produced by the ovaries

When pituitary adenoma is the cause of decreased estrogen production, an increase of which hormone os most frequently responsible ?

Prolactin

Which of the following statements is correct in aaesing GH deficiency ?

Pituitary failure may involve one, several, or all adenohyphophyseal hormones, but GH deficiency is usually found.

Which statement best describes the level of GH in patients with pituitary adenoma associated with acromegaly ?

Some patients require a glucose suppression test to establish a diagnosis

Hyperparathyroidism is most consistently associated with ?

Hypophosphatemia

(Inc serum Ca , dec serum phos)

Which statement reagarding the use of PTH is true ?

PTH levels differentiate primary and secondary cause of hypocalcemia

The best method of analysis for serum PTH involves using antibodies that detect ?

Both the amino-terminal fragment and intact PTH

Which of the following is most often elevated in hypocalcemia associated with malignancy ?

Parathyroid hormone related protein (PTHRP)

Steroids with a dihydroxyacetone group at C17 are sclassified as :

17-hydroxycorticosteroids

Which statement below regarding adrenal cortical dysfunction ?

Cushing's syndrome is associated with glucose intolerance

Which of the following statements about cortisol in Cushing's syndrome is true ?

24 hour urinary free cortisol is a more sensitive test than plasma total cortisol

Which of the following diseases is characterized by primary hyperaldosteronism caused by adrenal adenoma, carcinoma, or hypoplasia ?

Conn's disease

Which of the following is the most common cause of Cushing's syndrome ?

Overuse of Corticosteroids

Which of the following is the mechanism causing Cushing's disease ?

Excess secretion of pituitary ACTH

In which situation is the plasma or 24-hour urinary cortisol not consisent with the clinical picture ?

Evaluation of congenital adrenal hyperplasia

Which test is used to distinguish Cushing's disease (pituitary Cushing's) from Cushing's syndrome ?

Serum ACTH

Whic is the most widely used screening test for Cushing's syndrome ?

Overnight dexamethasone suppression test

Which test is the most specific for the establising a diagnosis of Cushing's disease (pituitary Cushing's) ?

Petrosal sinus sampling following corticotropin-releaseing hormone stimulation

Which of the statements below regarding the catecholamines is true ?

Plasma levels show both diurnal and pulsed variation

Which assay using 24 hour urine is considered the best single screening test for pheochromocytoma ?

Metanephrines

Which metabolite is most often increased in carcinoid tumors of the intestines ?

5-hydroxyindolacetic acid (5-HIAA)

Which statement regarding the measure ment of urinary catecholamines is true ?

24 hour urinary catecholamine assay avoids pulse variations associated with measurement of plasma catecholamines

Which method used to measure catecholamines is the least specific ?

Measurement of fluorescence following oxidation by potassium ferrocyanide

Which statement about sample collection for catecholamines and metabolites is true ?

24 hour urine creatinine should be measured with vanillymandelic acid, homovanillic acid, or metanephrines

Which statement below applies to both measurement of VMA and metanephrines in the urine ?

Both can be measured by specific HPLC and GC-MS asays

Thyroid hormones are derived from the amino acid ?

Tyrosine

Which statement regarding thyroid hormones is true ?

T₃ is about tenfold more active than T₄

Which of teh statements below regarding thyroid hormones is true ?

Total T₃ and T₄ are influenced by the level of thyroixine-binding globulin

Which of the following conditions increase total T₄ by increaseing thyroxine binding globulin (TBG) ?

Pregnancy or estrogens

Select the most appropriate single screening test for thyroid disease ?

TSH assay

The serum TSH level is decreased in :

Primary hyperthyroidism

Which assay is the most specific and sensitive test for diagnosing thyroid disease ?

Thyrotropin releaseing hormone (TRH)

Which of the following statements is true regarding reverse T₃ (rT₃₎  ?

Formed in the blood by degradation of T₄

A patient has an elevated serum T_3, and Free T₄ and a very low serum TSH. What is the most likely cause of these results ?

Primary hyperthyroidism

A serum thyroid panel reveals an increase in Total T_4, normal TSH , and normal Free T₄. What is the most likely cause of these results ?

Euthyroid with increased thyroxine-binding protein

Which statement about TSH and T₄ in early pregnancy is correct ?

TSH falls and thyroid hormone levels rise

In which case might a very low plasma TSH result not correlate with thyroid status ?

After high dose corticosteroid treatment

In which case below is qualitative analysis of the drug usually adequate ?

To determine whether the patient has been taking amphetamines

The term pharmokinetics refers to the :

Relationship between drug dose and the drug blood level

The term pharmacodynamics is an expression of the relationship between:

Drug concentration at target sites and physiological effect

The study of pharmacogenomics involves which type of testing ?

Testing for single nucleotide polymorphisms known to affect drug metabolism

Select the five pharmacological parameters that determine serum drug concentrations:

Liberation,absorbtion, distribution, metabolism, excretion

Which route of administration is associated with 100% bioavailbility ?

Intravenous

The phrase first- pass hepatic metabolism means that :

Some drug is matabolized from the portal circulation, reducing bioavailability

Which formula can be used to estimate dosage needed to give a desired steady state blood level ?

Dose per hour = clearance (milligrams per hour) x average concentration at steady state / f

Which statement is true regarding the V_d of a drug ?

V_d is the theoretical volume in liters into which the drug is distributes

For drugs with first order elimination, which statement about drug clearance is true ?

Clearance = elimination rate/serum level

Which statement about steady state drug levels is true ?

Oral dosing intervals result in peaks and troughs in the dose response curve

If too small a peak trough difference is seen for a drug given orally then :

Dose interval should be increased

If the peak level is appropiate but the trough level os too low at steady state, then the dose interval should:

Be shortened, but the dose per day not changed

If the steady state drug level is too high, the best course of action is to:

Decrease the dose

When should blood samples for trough drug levels be collected ?

Immediately before the next dose is given

Blood sample collection time for peak drug levels :

Varies with the drug, depending on its rate of absorbtion

Which could account for drug toxicity following a normally prescribed dose ?

Decreased renal clearance caused by kidney disease

Discontinuance of another drug

Altered serum protein binding caused by disease

All above:

Select the elimination model that best describes most oral drugs ?

One compartment, linear first order elimination

Drugs rapidly infused intravenously usually follow which elimination model ?

Biphasic or two compartment with serum level rapidly falling in the first phase

Which fact must be considered when evaluating a patient who displays signs of drug toxicity ?

Drug natabolites (eg-N-acetylprocanimide) may need to be measured as well as the parent drug toxicity

When a therapeutic drug is suspected of causing toxicityl, which specimen is the most appropriate for an initial investigation ?

Peak blood sample

For a drug that follows first order pharmacokinetics, adjusting of dosage to ahcive the desired blood level can be made using which formula ?

New dose=     current    _{x conc at steady state}

desired conc

For whcih drug group are both peak and trough measurement usually required ?

Aminoglycoside antibiotics

Which is the following statements about TLC for drug screening is true ?

A drug is identified by comparing the R_f value and staining to standards

The EMIT for drugs of abuse uses an :

Enzyme conjugated to a drug

Which statement about EMIT is true ?

Formation of NADH is monitored at 340 nm

Which statement below regarding FPIA is true ?

Separation of free and bound labeled antigen is not required

Quantitation of a drug by gas chromotography-mass spectroscopy (GC-MS) is usually performed in which mode ?

Selective ion monitoring

A urine sample is received in the laboratory with the appropriate custody control form and a request for drug of abuse screening. Which test result would be a cause for rejection of the sample ?

Creatinine level of 5 mg/dl

Which statement about the measurement of carboxyhemoglobin is true ?

Bichromatic analysis is required in order to eliminate interference by oxyhemoglobin

Which is the following statements about blood alcohol measurement is correct ?

Symptoms of intoxication usually begin when the level exceeds 0.05 % w/v

Which drug can be detected with ferric chloride in perchloric-nitric acids ?

Phenothiazines

Which specimen is the sample of choice for lead screening ?

Whole blood

Which of the following enzymes can be used to measure plasma or serum salicylates ?

Salicylate hydroxylase

Which of the following tests is least essential to the operation of a ER ?

Lead

Which of the following tumor markers is classified as a tumor suppressor gene ?

BRCA-1

In general , in which of the following situations is the analysis of a tumor marker most useful ?

Testing for recurrence 

Which of the following enzymes is increased in persons with prostate and small cell lung cancer ?

Creatine kinase-1 (CK-1 / CK-BB)

often present w/maligancies

Which of the following is the best analyte to monitor the recurrence of ovarian cancer ?

CA-125

Which tumor marker is associated ith cancer of the urinary bladder ?

Nuclear matrix protein

A person presents with a Cushingoid appearance and an elevated 24-nr uring cortisol level. Plasma adrenocotropic hormone(ACTH) is very elevated and the clinicial suspects the cause is ectopic ACTH production. Which test would be most useful in substantiating this diagnosis ?

Alkaline phosphatase isoenzymes

Which of the following statements regarding the Philadelphia chromosome is true ?

It results from a translocation of the long arm of chromosomes 9 and 22

What is the primary clinical utility of measuring CEA ?

Monitoring for recurrence of cancer

Which tumor marker is used to determine the ussefulness of trastuzumab(Herceptin) therapy for breast cancer ?

HER-2/neu

A person is suspected of having testicular cancer. Which type of hCG test would be most useful ?

Plasma immunoassay for intact hCG and the β-hCG subunit

A patinet is treated for a germ cell tumor has a total and free bhcg assay performed one week prior to surgery. The result is 40,000 and one week following surgery the result is 5000. Chemo is started and one week later the result is 10,000. What does this indicate ?

Transient hCG increased by chemotherapy.

Which set of results for ER and PR is associated with the highest likelhood of a favorable response to treatment with estrogen suppression therapy (tamoxifen)?

ER positive, PR positive

(receptor assays performed on breast tissue bx to determine the potential response to tamoxifen)

Which type of cancer is associated with the highest level of AFP ?

Hepatoma

Which of the following assays is recommended as a screening test for colorectal cancer in persons over 50 years old ?

Occult blood

Which of the following substances is used to determine the rick of developing cancer ?

p53 gene

A person has an elevated 24 hour urinary homovanillylic acid (HVA) and vanillymandelic acid (VMA). Urinary metanephrines, chromogranin A, and neuron-specific enolase are also elevated but 5-hydroxyindoleacetic acid is within the reference range. What is the most likely diagnosis ?

Neuroblastoma

In which of the following conditions is the PSA least likely to be increased ?

Post-digital rectal examination

Which if the following statements regarding PSA is true ?

Free PSA below 25% is associated with malignant disease

A 55 year old male with early stage prostate cancer diagnosed by biopsy had his prostate gland removed. His PSA prior ro surgery was 10.0 . If the surgery was successful in completely removing the tumor cells, what would the PSA result be 1 month after surgery ??

Undectectable

Which of the procedures below can be used to evaluate a new glucose mehtod for proportional error ?

Add 5.0 mg of glucose to a 1.0 mL of a serum of knwon concentration and measure

(proportional error is percentage deviation from the expected result and affects the slope of the calibration curve. It causes a greater absolute error as concentration increases?

Which of the two instruments can be assumed to have a narrower bandpass ?  Assume that wavelength is accurately calibrated.

The instrument giving the highest absorbance for a solution of 0.1 mmol/L NADH at 340 nm.

A patient wha has a positive urinalysis for glucose and ketones has a glycoslylated Hgb of 4.0 % A fasting glucose performed the previous day was 180 mg/dL. Assuming QC was ok, what would you do ?

Request a new sample and repeat the glycosylated Hgb

Laboratory results on a patient from the ED are :

Glucose = 1100 mg/dL

Na = 155 mmol/L

K = 1.2 mmol/L

Cl = 115 mmol/L

TCO₂ = 3.0 mmol/L

Explanation for these results ?

Sample is drawn above the intravenous catheter

A quantitative urine glucose level was determined to be 160 mg/dL by the Trinder glucose oxidase method. The sample was refrigerated overnight and the glucose the next day was 240 mg/dL with the polarographic method. What is the most likely cause of the discrepancy ?

High levels of reducing substances interfering with the Trinder reaction

A tech is asked to use the serum from a clot tube left over from a chemistry profile run at 8 am for a stat ionized calcium. The tech should ?

Request a new sample

( ionized ca is pH dependant and heparin is preferred)

A quantitative sandwich enzyme immunoassay for intact serum hCG was performed on week 4 and the result was 40,000 mIU/ml(ref 10,000-80,00) A clinician suspects a molar pregnancy and requested that the lab repeat the test checking for the hook effect. What process would identify this problem ?

Perform a serial dilution of the sample and repeat the test