Liver Function Tests and Enzymes

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    Normal liver functionsA. Metabolic Functions:

    glucose homeostasis

    Protein synthesis

    Lipid synthesis

    tected by liver enzymes

    B. Synthetic Functions:

    AlbuminPT & APTT

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    D. Catabolic Functions:

    including hormones and serum proteins, are

    catabolized by the liver.Ammonia (NH4)

    E.

    Excretory Functions:The principal excretory product of the liver is bile

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    Liver function tests

    Noninvasive method of screening for thepresence of liver dysfunction

    Allows recognition of general type of disorder

    To assess the severity and occasionallyallow prediction of outcome

    To follow the course of the disease, evaluate

    response to treatment, and adjust treatmentwhen necessary

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    General categories of tests

    Tests of the capacity of the liver to

    transport organic anions and metabolize

    drugsEg. S bilirubin, s bile acids, BSP (Brosulphalein) etc

    Measures ability of the liver to clear endogenous or exogenous

    substances from the circulation

    Tests to detect injury to hepatocytesAll the enzyme tests

    Most commonly done and most useful are

    aminotransferases and alkaline phosphatase

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    Tests of the biosynthetic capacity of the liver

    Tests to detect fibrosis in the liver

    Tests for chronic inflammation or altered

    immunoregulation

    Eg. S albumin, prothrombin time

    Eg. Type 4 collagen, Fibrotest etc

    Immunoglobulins and specific antibodies

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    Common serum liver chemistry tests

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    Normal values

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    Case study 1

    A woman, 35 years of age, complained of abdominal pain and dark urine. She was

    clinically mildly jaundiced. Her liverfunction tests were as follows:

    Albumin 36 g/L (3448)

    Protein 83 g/L (6585)

    Total bilirubin 45 mol/L (224)

    GGT 439 U/L (

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    Case study 2

    A man, 39 years of age, had the following results as part of an insurance medical:

    Albumin 37 g/L (3448)

    Protein 72 g/L (6585)

    Total bilirubin 13 mol/L (224)

    GGT 46 U/L (

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    Case study 3A man, 66 years of age, presented with weight loss and fatigue. He had a normocytic

    anaemia. His LFTs were as follows:

    Albumin 22 g/L (3448)

    Protein 59 g/L (6585)

    Total bilirubin 12 mol/L (224)

    GGT 926 U/L (

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    Initial approach to the evaluation of

    abnormal liver enzyme tests

    Asymtomatic or symptomatic

    History and physical

    Alcohol consumption

    Risk factors for viral hepatitis - IV drug abuse, sexual promiscuity,

    homosexual relations, tattoos, nonsterile body piercing, blood and blood

    products, medications, herbal or alternative med., occupational exposure to

    toxins

    Diabetes, obesity, hyperlipidemia

    Family history - Wilsons dis, hemochromatosis, autoimmune diseases

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    Evaluation of abnormalities of ALT

    (SGPT) and AST (SGOT) levels

    AST and ALT are markers of hepatocellularinjury

    Participate in gluconeogenesis, transfer of amino

    groups from aspartate or alanine to ketoglutaricacid to form oxaloacetete or pyruvate.

    AST present in cytosol and mitochondria in liver,cardiac muscle, skeletal muscle, kidney, brain,pancreas, lungs, WBC and RBC.

    ALT a cytosolic enzyme, highest concentration inthe liver

    ALT considered a liver specific enzyme

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    Useful paradigm to categorize

    increased levels of AST, ALT

    Mild AST, ALT elevation (less than 5

    times ULN) - ALT predominant or AST

    predominantAST, ALT greater then 15 times normal

    Elevations in the intermediate range -

    less useful for limiting the DD, caused bydiseases from both above categories

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    Acute Liver Disease

    Reliable history

    Ratio of SGOT(AST) to SGPT(ALT) is atleast 2:1

    Reflects low level of activity of SGPT

    SGOT rarely exceeds 300 IU

    Higher values - seek additional cause of liver

    injury A GGT (gammaglutamyl transferase) twice

    normal and AST/ALT ratio of 2:1 or more,highly suggestive of alcohol abuse

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    NAFLD

    Hepatic steatosis (fatty liver) and NASH

    Asymptomatic increase in transaminases

    Raised BMI, Type 2 DM and hyperlipidemia

    No evidence of clinically relevant alcohol use Probably commonest cause of mild

    transaminase increases

    AST/ALT ratio usually < 1:1 in the absence of

    cirrhosis Values < 250 IU usually

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    DD of moderately elevated

    aminotransferases (5 to 15 times ULN)

    Wide range of liver diseases

    ALT, AST less useful in determining

    cause Entire spectrum of liver diseases causing

    mild or severe aminotransferase

    elevation

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    DD of severe elevations of ALT,

    AST (> 15 times ULN)

    Relatively limited

    Indicate marked hepatocellular injury or

    necrosis Drug induced - acetaminophen

    Occupational/environmental toxins -CCl4

    Ischemic hepatitis

    Viral hepatitis - A, B, D, E, Herpes

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    Suggested algorithm for evaluating raised transaminases

    PMJ 2003

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    Other enzyme tests for hepatocellular

    necrosis

    Glutamate dehydrogenase

    Isocitrate dehydrogenase

    Lactate dehydrogenase

    Sorbitol dehydrogenase

    More useful as marker for

    Hemolysis,

    Myocardial infarction

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    Enzymes for the detection of cholestasis

    Alkaline phosphatase

    Present in nearly all tissues - isoenzymes

    Localised in the microvilli of the bile canalicus in the liver

    Also present in bone, intestine, placenta, kidney and wbcElevation may be physiological or pathological

    Physiological

    In tissues undergoing metabolic stimulationThird trimester of pregnancy

    Adolescence

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    Normal adult serum AP is from liver andbone

    Intestine contributes about 15%

    Several procedures used to measure activity- differs in substrates used, end productsmeasured, etc

    Isoenzymes differ in reactions in variousassay systems

    Hence different units such as IU, KA,Bodansky

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    Elevation of s. alkaline

    phosphatase

    Isolated

    Associated with hyperbilirubinemia

    (cholestatic disorders) May be sole abnormality in many

    cholestatic or infiltrative diseases

    To be interpreted in the clinical setting ofhistory and physical examination if soleabnormality

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    When SAP elevation is detected

    Repeat the test

    Confirm the hepatic origin

    If medications suspected, discontinue them and repeat test

    Persistently elevated SAP - evaluate for

    Serum gammaglutamyl transferase

    5-Nucleotidase

    AP isoenzymes

    Cholestatic liver disease

    Infiltrative liver disease

    Biliary obstruction

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    AP elevation upto 3 times ULN

    > 3 times ULN

    Nonspecific

    Occurs in all types of liver disorders

    Viral hepatitis

    Cirrhosis

    Infiltrative diseases of the liver

    CHF etc

    Cholestatic disorders Extrahepatic

    Intrahepatic

    Infiltrative disorders

    Mets

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    Suggested algorithm for evaluating a

    raised s.alkaline phosphatase

    PMJ 2003

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    Gammaglutamyl transferase

    (-glutamyl transpeptidase)

    Found in hepatocytes and biliary epithelial cells

    Sensitive for hepatobiliary disease but limited by lackof specificity

    With other enzyme abnormalities, raised GGT wouldsupport a hepatobiliary cause

    Can confirm hepatic source for a raised AP

    Raised GGT and raised transaminases with ratio ofAST to ALT 2:1 or more suggestive of ALD

    Medications can cause mild rise

    Normal range 0 to 30 IU/L

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    Causes of raised serum

    gammaglutamyl transferase (SGGT)

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    5-Nucleotidase

    Normal 0.3 to 3.2 Bodansky units

    Spectrum of abnormality similar to that of

    Serum AP Specificity for hepatobiliary disease

    May be used to confirm hepatic origin of

    elevated Serum AP

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    A 63-year old man presented with haematemesis. He had lost 12

    kg of weight over the preceding 6 months. Gastroscopy showed

    a carcinoma of the stomach. The following results .

    urea 5.0 mmol/l (1.7-6.7) creatinine 66 mol/l (60-115) total protein 55 g/l

    (60-80) albumin 23 g/l (35-50) calcium 1.86 mmol/l (2.1-2.6) total bilirubin

    15 mol/l (

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    RE cell plasma hepatocyte

    HEME UCB UCB

    +

    albumin

    UCB+ligandin

    BMG

    BDG

    bile

    urobilinogen stercobilinogen

    Bilirubin

    UDP-glucoronyltransferase

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    Isolated unconjugatedhyperbilirubinemia

    IDB fraction > 85% of total bilirubin

    1. Increased production

    hemolysis

    ineffective erythropoiesis : folate, IDA drugs : rifampicin resolution of hematoma

    2. Defects in hepatic uptake/conjugation Gilberts syndrome Crigler-Najjar syndrome

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    DB > 50% of total bilirubin

    cant differentiate obstruction and

    parenchymal disease Delta fraction

    Conjugated bilirubin tightly bound to albumin

    tendency of hyperbilirubinemia to resolvemore slowly than other biochemical tests

    Conjugated hyperbilirubinemia

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    The following results were obtained from a patient who presented with mild

    jaundice:

    Albumin 45g/l (35-50), total bilirubin 43mol/l (

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    A medical student recovering from a bout of 'flu noticed he was

    slightly jaundiced. These results were found:

    total bilirubin 60 mol/l (

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    A 14-year-old boy has the sudden onset of severe abdominal

    and back pain. On physical examination his abdomen is

    diffusely tender. He has scleral icterus. Laboratory studies

    include a hemoglobin electrophoresis that reveals 98% Hgb S,

    1% Hgb A2, and 1% Hgb F. Which of the following serum

    analytes is likely to be increased the most in this boy?

    A Creatine kinase (CK)

    B Amylase

    C Alkaline phosphataseD Lactate dehydrogenase (LDH)

    E Alanine aminotransferase (ALT)

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    A 30-year-old woman has developed nausea and vomiting over

    the past week. On physical examination she has mild scleral

    icterus. A hepatitis panel reveals a positive HAV IgM, negative

    HBsAg, positive HBsAb, and negative HBcAb. Which of the

    following laboratory tests is most likely to be abnormallyelevated in this woman?

    A Creatine kinase (CK)

    B Amylase

    C Alkaline phosphataseD Lactate dehydrogenase (LDH)

    E Alanine aminotransferase (ALT)

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    A 42-year-old woman has had intense pruritus for the past 3

    months. She is becoming increasingly jaundiced. On physical

    examination she has scleral and skin icterus. A liver biopsy is

    performed and on microscopic examination shows destructionof intrahepatic bile ducts leading to marked portal fibrosis.

    Which of the following laboratory test findings is she most

    likely to have?

    A Markedly decreased serum immunoglobulin A

    B Decreased serum ceruloplasmin

    C Increased serum alpha-fetoprotein

    D Decreased serum alpha-1-antitrypsin

    E Positive serum anti-mitochondrial antibody

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    Increased unconjugated plasma bilirubin is mostly seen in

    A. Sickle cell anemia

    B. Drug induced cholestasis

    C. Liver cirrhosis

    D. Carcinoma of the liver

    E. Hepatitis C infection

    Excess urobilinogen in urine is seen in

    A.. Hemolytic anemia

    B. Obstructive jaundiceC. Primary biliary cirrhosis

    D. New- born babies

    E. Acquired immunodeficiency patients

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    The carrier protein for bilirubin is

    A .Pre albumin

    B.Transferrin

    C. AlbuminD. Haptoglobulin

    E. Alpha- globulin

    BILE ACID ( BILE SALT) METABOLISM

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    BILE ACID (= BILE SALT) METABOLISM

    From cholesterol metabolism are chenodeoxycholic acid and cholic acid, by 7--

    hydroxylation

    Conjugated to glycine or taurine (this increases their solubility).

    In the GIT, bacterial enzymes deconjugate and dehydroxylate the primary bile

    acids and convert them to the secondary bile acids lithocholic acid and deoxycholic

    acid.

    Most of the bile acids in the GIT are reabsorbed into the portal circulation (75%in the ileum and 10% in the colon), taken up by the liver again and re-excreted

    (enterohepatic circulation). Re-uptake of bile acids by the liver is highly efficient,

    but sensitive to liver damage

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    A 50-year-old man with a history of alcohol abuse is

    found down with a decreased level of

    consciousness. On examination he has palmarerythema, spider angiomata of the skin of his upper

    extremities, fetor hepaticus, and asterixis. Which of

    the following blood analytes is most likely to be

    elevated in this man?

    A Ammonia

    B Cholesterol

    C CreatinineD Creatine kinase BB

    E Glucose

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    Albumin

    depends on nutrition, hormonal factors,vascular integrity, catabolism, loss in stooland urine

    not specific for liver disease T1/2 = 19-21 days

    Not a reliable indicator of acute liver disease Levels fall in progressive disease, reflects synthetic

    function

    Correlates with prognosis in Chronic Liver Disease

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    A 44-year-old man has become increasingly lethargic over the

    past month. On physical examination his liver span is increasedand there is an abdominal fluid wave. Laboratory studies show a

    serum AST of 240 and an ALT of 155 U/L. The total serum

    bilirubin is 2.4 mg/dL with direct bilirubin of 1.6 mg/dL. His

    serum alkaline phosphatase is 55 U/L. The serum albumin is 2.6

    g/dL with total serum protein of 4.9 g/dL. The serum amylase is

    72 U/L. Which of the following is the most likely diagnosis?

    A Chronic pancreatitis

    B Gilbert syndrome

    C Chronic alcoholismD Acute viral hepatitis

    E Autoimmune hemolytic anemia

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    Prothrombin timeprolonged :

    vitamin K deficiency (malnutrition,malabsorption, antibiotics)

    massive transfusion congenital disease liver disease warfarin DIC

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    Prothrombin time

    in vit K deficiency, vit K 10 mg SC decreasesprolonged PT >30% within 24 hrs

    INR (international normalised ratio)

    More often tested now

    Standardising reports of PT

    Avoids interlab variabilityINR = [Patient PT/mean control PT] ISI

    ISI - international sensitivity index

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    Prothrombin time

    The liver synthesizes coagulation factors except

    FVIII

    Most present in excess, clotting abnormality

    occurs only when substantial impairment in

    ability of liver to synthesise the CF

    PT : FI, II, V, VII, IX and X

    T1/2 FVII 6 hrs. (shortest) prognosis : acute, chronic hepatocellular

    disease

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    Modified Child-Turcotte-Pugh score for gradingseverity of liver disease

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    Take home message

    initial evaluation : assess in clinicalcontext

    classified in 3 groups

    1. synthetic function : albumin, clotting

    time2. cholestasis : bilirubin, ALP, GGT

    3. hepatocyteinjury : AST, ALT

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    misnomer

    Does not effectively assess actual function

    not always specific for the liver limited information regarding presence or

    severity of complication

    Liver Function Tests

    Liver Chemistry Tests

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    When to refer for a specialist opinion?

    Unexplained liver abnormalities > 1.5 times

    normal on 2 occasions, a minimum of 6

    months apart

    Unexplained liver disease with evidence of

    liver dysfunction (hypoalbuminemia,

    hyperbilirubinemia, prolonged PT or INR)

    Known liver disease where treatment beyondwithdrawal of the implicating agent is

    required Limdi et al, Postgrad Med J 2003

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    What tests to do before referral?

    Consider the following;

    Screen for viral hepatitis

    Antinuclear antibodies

    Ceruloplasmin in pts < 40 yrs

    Iron studies - S ferritin, transferrin saturation

    US of the hepatobiliary system

    IgM anti HAV

    HBsAgAnti HCV

    PMJ 2003

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    Enzymes

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    Nomenclature

    First were given emperical name eg

    pepsin

    Then using name of substrate + suffixase .eg

    Urease :hydrlyzing urea

    Amylase: hydrolze amylum(Starch)Phosphatase:Hydrolyzing phosphat

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    Normal plasma enzyme

    Its level reflects the balance between therate of synthesis & release into plasma duringcell turnover, and the rate of clearance from thecirculation.

    (S+E ES P(reaction product +E(Free enzyme)

    Its level depends on:

    rate of release fr damaged cells rate of damage is occuring

    extent of cell damage

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    In absenceof cell damagerate ofrelease depends : Rate of cell proliferation

    Degree of induction of enzymesynthesis

    All these factors are balanced by the rate

    of enzyme clearance fr the circ.

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    Localization of Damage How do we make specific diagnosis?

    Diagnosticprecision is improved by:

    1. Estimate > than 1 enzyme

    2. isoenzyme determinationexist inmore than 1 form, may be separated by theirdifferent physical or chemical properties

    3. serial enzyme estimationpersistently

    raised activity suggests chronic/impairedclearance

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    Causes ofNon-specific raisedplasma enzymes activities change in plasma enzyme activity is

    pointing towards a specific disease, wemust exclude nonspecific causes.

    e.g. Elevated AST can be due to MI,moderate exercise, muscle exercise orlarge IM injection.

    So, we can do a few discriminating testssuch as CK-MB, troponin, CK

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    Causes of Markedincrease in CK Shock & Circulatory collapse

    MI

    Muscular dystrophies &Rhabdomyolysis(breakdown of skeletal muscle)

    Plasma CK is increased in all types of muscular

    dystrophy.

    Not in neurogenic muscle disorder e.g.poliomyelitis, myastenia gravis, parkinson.

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    Moderate increase in CK Muscle injury

    Post-op ( 1 week)

    Physical exertion only after moderate exercise,muscle cramp or after an epileptic fit

    After IM injection

    Hypothyroidism (thyroxine catabolism of enzyme)

    Alcoholism (alcoholic myositis) CVA & Head injury cases

    Those predispose to Malignant Hyperpyrexia

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    Isoenzymes of CK CK consist of 2 protein subunit M & B

    When combined can form 3 isoenzyme :CK BB, CKMB & CK MM(CK-1 , CK-2 & CK-3)

    CK MM is the predominant CK in skeletal & cardiacmuscle.

    In Cardiac muscle : CK MB 35% of

    total CK activity

    In Skeletal muscle : CK MB

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    IsoenzymeCK CK BB is present in high conc. In brain &

    in smooth muscle of GIT & Genitaltracts.

    Can be raised during parturition

    Also has been reported, that after braindamage & in association with malignant

    tumours e.g. bronchus, prostate &breast, there is a raised CK BB.

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    A 55-year-old man with unstable angina presents

    with a history of chest pain that has been

    worsening over the past eight hours. The pain

    radiates down his left arm. On physical

    examination he is now diaphoretic, with pulse of

    104/minute and an irregular cardiac rhythm.

    Which of the following is the most appropriatelaboratory test to order on this man?

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    A) CK-MB

    B) Total CK

    C) ASTD) Total LDH

    E) LDH-1

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    A 51-year-old man with a history of

    diabetes mellitus suddenly collapses. On

    physical examination he is afebrile but

    his heart rate is 90/minute and irregular.

    Laboratory studies show total creatine

    kinase (CK) 495 U/L with an MB

    isoenzyme fraction of 10%. Which of thefollowing is the most likely diagnosis?

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    A Blunt force injury to the abdomen

    B Acute myocardial infarction

    C Cerebral infarction D Trichinosis

    E Prostatic adenocarcinoma

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    Amylase Is a hydrolase that breaks down glycogen &

    starch

    Present in high conc. in saliva & pancreatic

    juice and can be extracted from tissues likegonads, fallopian tubes, skeletal muscle &adipose tissue

    Can be excreted in urine due to lowmolecular weight.

    Plasma amylase activity help diagnoseacute pancreatitis and other intra & extraabdominal conditions which cause similarpain.

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    Causes of Raised Amylase Marked Increase (5-10 times UARL)

    Acute pancreatitis

    Severe glomerular impairment

    Severe DKAPerforated peptic ulcer ( esp. in lesser sac)

    Moderate Increase ( up to 5 times UARL)

    Other acute abdominal dis.:

    perforated PUacute choleycystitis

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    ContModerate increaseof AmylaseIntestinal obstruction

    Abdominal trauma

    Ruptured ectopic pregnancy

    Salivary gland disorder

    mumps

    salivary calculi

    Sjogren syndrome

    post injection of contrast medium into salivary gland

    for sialography Others morphine administration,( spasm of s.

    oddi), MI, DKA, severe glomerular dys(fx), acutealcoholic intoxication & macroamylasaemia

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    Macroamylasaemia In some pts, a high plasma amylase activity

    is due to low renal excretion of the enzymedespite normal glomerular f(x).

    Symptomless Thought that either the enzyme is bound to a

    high molecular wt plasma component e.g.protein

    Or amylase molecules form large polymersthat cant pass through glomerularmembrane

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    Pancreatic Pseudocyst If plasma amylase activity does not fall after

    an attack of acute pancreatitis, there may bea leakage of pancreatic fluid into lesser sac.

    Urinary amylase are high, so this is anindication to do a urine amylase activitywhich is inappropriately low relative to theplasma activity if got macroamylaseamia or

    glomerular impairment. So, this differentiates it from

    macroamylaseamia

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    Isoenzymes of Amylase It is rarely necessary to identify the isoezymes.

    Can be distinguished by electrophoresis / by usinginhibitor derived from wheat germ

    30-40% of total plasma amylase activity is due topancreatic (p) isoenzyme & remainder is of salivary.

    Specific estimation of p-isoenzyme is of no

    additional diagnostic value to differentiate acutepancreatitis from non-pancreatic abdominal

    emergencies.(due to leaked pancreatic amylase intoperitoneal area gets into bldstream)

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    A 40-year-old man with HIV infection is

    receiving highly active antiretroviral

    therapy (HAART) that includes protease

    inhibitors. He has developed acute

    abdominal pain over the past day, along

    with nausea and vomiting. On physical

    examination he has peripheral fatwasting but a prominent dorsocervical fat

    pad. Laboratory studies show a serum

    triglyceride of 1440 mg/dL and serum

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    Which of the following is the most likely

    diagnosis?

    A) HepatitisB)Appendicitis

    C) Cholecystitis

    D) PancreatitisE) Pyelonephritis

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