The Clinical Chemistry Lab

1
The Clinical Chemistry Lab

• Vicki S. Freeman, Ph.D.

2
Objectives

• Upon completion of lecture, discussion, case
  studies and laboratory, the student will be able
  to
• Quality Control and CLIA Regulations
• Explain the importance of QC in the lab
• Define sensitivity, specificity, shift, trend,
  precision , accuracy and reliability
• Describe the 6 aspects of quality control
• Classify procedures according to the CLIA
  regulations
• List the Quality Assurance requirements mandated
  in the CLIA regulations
• Carbohydrates
• Differentiate types of diabetes by clinical
  symptoms and laboratory data
• Type 1
• Type 2
• Gestational diabetes
• Impaired glucose tolerance

3
Objectives (Cont)

• Upon completion of lecture, discussion, case
  studies and laboratory, the student will be able
  to
• Carbohydrates (Continued)
• Relate expected laboratory results and clinical
  symptoms to the following metabolic complications
  of diabetes
• Ketoacidosis
• Hyperosmolar coma
• Describe the used of hemoglobin A1C and
  microalbumin in the long term monitoring of
  diabetes
• Lipids and Cardiac Risk
• Discuss cholesterol, LDL cholesterol, HDL
  cholesterol, lipoproteins and triglycerides as
  predictors of cardiovascular risk
• Calculate a LDL cholesterol, given total
  cholesterol, triglyceride and HDL results

4
Quality Control

• Purpose of QC is to
• assure the reliability of patient data obtained
  from a procedure
• monitor variables that can alter data
• Patient data is unknown information and known
  samples must be run concurrently

5
Terms

• Precision
• the reproducibility of the result
• Accuracy
• the closeness of the measured result to the true
  value
• Reliability
• the ability to maintain both precision and
  accuracy

6
Quality Control

• Precision
• Accurate
• Reliability

7

• Shift
• 6 or more consecutive values distributed above or
  below the mean
• Trend
• A continual increase or decrease in 6 or more
  consecutive values

8
Quality Control

• Shift
• Trend
• Outliers

9
6 Aspects of Quality Control

• Sample collection
• Method of analysis
• Proper control material
• QC monitoring
• Instrument maintenance
• Documentation

10
CLIA 88

• Waived tests
• Moderate complexity tests
• High complexity tests
• Provider-performed microscopy

11
Waived Test Category

• UA dipstick
• Spun hematocrits
• Hemoglobin
• Sedimentation rate
• Fecal occult blood
• UA pregnancy test

• Ovulation tests
• Single analyte instrument
• Hemacue
• Glucose
• Total cholesterol

12
Provider-performed Microscopic

• Wet mounts
• vaginal
• cervical
• skin
• KOH preparations
• Pinworm exams
• Fern tests
• UA sediment exam

• Postcoital direct
• vaginal and cervical mucus
• Nasal granulocytes
• Fecal leukocytes
• Qualitative semen analysis

13
Common Tests in POLs

• Hemoglobin
• Hematocrit
• Dipstick UA
• Occult Blood
• Strep A (ag)
• UA pregnancy

• Glucose
• Cholesterol
• Triglycerides
• BUN
• Uric Acid
• Cholesterol
• HDL Cholesterol

14
Quality Assurance

• Vicki S. Freeman, Ph.D.

15
Quality Assurance Program

• Written laboratory procedure manual
• Specimen collection and identification
• Methodologies
• Reference Ranges
• Quality control
• Preventive maintenance
• Record keeping

16
Profile Groups

• Carbohydrates
• Lipids
• Enzymes
• Cardiac Function
• Liver Function
• Renal Function

• Electrolytes
• Parathyroid Function/ Calcium Metabolism
• Acid/Base Balance
• Pancreatic Function
• Prostate

17
Carbohydrates

• Hyper and Hypoglycemia

18
Classes of Hyperglycemia

• Diabetes Mellitus
• Impaired Glucose Tolerance
• Gestational Diabetes

19
Diabetes

• A syndrome characterized by inappropriate
  hyperglycemia with chronic microvascular
  complications.
• Upper limit of 100 mg/dl on the FPG as the upper
  limit of normal blood glucose

20
Diabetes Mellitus

• Types
• Type 1 (Type I) -Insulin Dependent Diabetes
  Mellitus
• IDDM
• Type 2 (Type II) -Non Insulin Dependent Diabetes
  Mellitus
• NIIDM
• Other Types - Secondary

21
TYPE 1
TYPE 2
Destruction of the B-cells
Resistance to Insulin
Absolute Deficiency of Insulin
Relative Deficiency of Insulin
22
Type 1 (Type I) - IDDM

• Characteristics
• Abrupt Onset
• Insulin Dependent
• Ketosis-prone
• Genetic related - HLA Dw4 related
• Islet Cell Antibodies
• 10 - 20 of all diabetes

23
Type 2 (Type II) - NIDDM

• Characteristics
• Little or no symptoms
• Does not exhibit the characteristics of IDDM
• Have high basal insulin levels - develop insulin
  resistance
• Decreased of insulin receptors in
  insulin-sensitive tissues
• Subclasses
• Non-obese
• Obese - 60 - 90 of all diabetics
• Further divided by the type of treatment the
  patient receives (Insulin, oral hypoglycemic,
  diet)

24
Other Types - Secondary

• Destroyed pancreas
• Pituitary Hyperfunction
• Cushings Disease

25
Diagnosis of Diabetes Mellitus

• Classic symptoms a casual plasma glucose
  concentration gt200 mg/dl
• Fasting venous plasma glucose concentrations gt126
  mg/dl
• 2 hour post prandial gt200 mg/dl
• Any of the 3 criteria must be confirmed on a
  subsequent day by any of the 3 methods.

26
Diagnosis of Diabetes Mellitus

• Classic symptoms of diabetes and hyperglycemia
• Laboratory Tests
• Preferred - Fasting venous plasma glucose
• gt 126 mg/dl on more than one occasion
• Impaired fasting plasma glucose 100 mg/dl - 126
  mg/dl
• Casual plasma glucose concentration gt200 mg/dl
• Not recommended - Screening test - 2 hour post
  prandial
• OGTT value of gt200 mg/dl in 2 hr sample
• Normal lt140 mg/dl
• Impaired GTT 140 - 199 mg/dl
• Abnormal gt200 mg/dl
• Any of the 3 criteria must be confirmed on
• a subsequent day by any of the 3 methods

27
Glucose Curves
28
Gestational Diabetes

• Diagnosed by any two of the following
• a fasting plasma glucose of more than 105 mg/dl
• a 1-hour glucose level of more than 190 mg/dl
• a 2-hour glucose level of more than 165 mg/dl
• or a 3-hour glucose level of more than 145 mg/dl

29
Specimen

• Overnight fast
• New evidence of diurnal variation with FPG higher
  in AM
• Plasma
• NaFloride
• if cannot be separated from cells within 60
  minutes
• Anticoagulated (oxalate)
• Whole blood values 11 lower than plasma
• Heparinized plasma values 5 lower than serum
• Capillary vs venous blood
• Fasting state (2 mg/dL difference)
• After a glucose load, capillary values 20-25
  higher

30
Monitoring Therapy

• Day - to - day control
• Self Monitoring Blood Glucose (SMBG)
• Long term
• Hemoglobin A1C
• Shows a direct relationship with the glucose
  level over the preceding 2-3 months
• Microalbumin
• Monitors Monitors kidney function
• Urine glucose - obsolete
• Urine ketones - fat breakdown products

31
Glycosylated (glycated) Hemoglobin (GHb or
HgbA1c)

• ADA Guidelines - Glycosylated hemoglobin
• Glucose attaches to tissues and proteins,
  including hemoglobin
• Measures of hgb that has been modified by
  glucose
• Shows a direct relationship with the glucose
  level over the preceding 2-3 months
• A valuable tool for monitoring glycemia,
• Normal levels range from 3-6
• Should be maintained at lt7 (some sources say 6)
• Re-evaluate treatment regimen if GHb gt8
• Should be measured at less than 2 x/year (if
  diabetic is well controlled otherwise, every 3
  months)

32
Approximate correlation between A1C level and
mean plasma glucose levels
HbA1C Mean plasma glucose Mean plasma glucose
mg/dl mmol/l
6 135 7.5
7 170 9.5
8 205 11.5
9 240 13.5
10 275 15.5
11 310 17.5
12 345 19.5
33
Microalbumin

• Diabetes is leading cause of end-stage real
  disease
• Microalbumin- Monitors kidney function
• Also a marker of increased risk of cardiovascular
  morbidity and mortality
• Annual testing is recommended
• Microalbuminuria defined as excretion of
• 30-300 mg of albumin/24hrs or
• 20-200 ?g/min or 30-300 ?g/mg creatinine
• On 2 of 3 urine collections

34
Acute Complications

• Ketoacidosis due to lack of insulin/stress, can
  result in death (assoc. with Type I)
• B HCO3-, B pH, A glucose
• Hypoglycemia - with too much insulin - results in
  coma
• Hyperosmolar coma (assoc. with Type II)
• A blood osmolarity
• A glucose

35
Chronic Complications

• Correct Management of diet and insulin,
• Avoid further complications of the disease
• Retinopathy - blindness 50 after 10 years
• Nephropathy - Renal disease
• proteinuria, increased BUN and creatinine
• Neuropathy -
• poor sensation, ulceration of skin, may lead to
  amputation of limbs
• Accelerated macrovascular disease - CAD, CVA

36
Hypoglycemia

• Decreased fasting glucose lt50 mg/dl
• Fasting
• Caused by pituitary/adrenal insufficiency,
  pancreatic islet cell hyperplasia, islet cell
  tumors
• Other causes may be from drugs, alcohol, insulin
• Triad of characteristics (Whipple's Triad)
• Hypoglycemic symptoms
• Simultaneous demonstration of decreased plasma
  glucose
• Relief of symptoms with glucose administration
• Postprandial (or reactive)
• Seen after gastric surgery - food is absorbed too
  fast
• Idiopathic - following extreme stress
  (catecholamines)
• Spontaneous recovery

37
Diagnosis of Hypoglycemia

• Diagnosed by looking for the cause
• Thrust of the clinical evaluation is to rule out
  insulinomas.
• Hypoglycemia in insulinomas are related to
  excessive and inappropriate production of insulin
  - insulin levels are important in making the
  diagnosis

38
Diabetes Case Study 1

• A 40-year-old African American woman
  (nonpregnant) has symptoms suggestive of
  diabetes. On two occasions, the fasting plasma
  glucose (FPG) is 130 mg/dL and 135 mg/dL.
• What is the next diagnostic or therapeutic step?

39
Diabetes Case Study 2

• A 35-year-old Caucasian female (nonpregnant) has
  FPG concentrations on two occasions of 120 mg/dL
  and 124 mg/dL without symptoms suggestive of
  diabetes.
• How would this patient would be classified?

40
Diabetes Case Study 3

• A 72 year old male presents with numbness in the
  legs and frequent urination. A 4 hour glucose
  tolerance is ordered. The results are
• FPG 160 mg/dL 2 hr 220 mg/dL
• 1/2 hr 205 mg/dL 3 hr 195 mg/dL
• 1 hr 260 mg/dL 4 hr 165 mg/dL
• A follow up Hgb A1c was ordered.
• Does this gentleman have diabetes?

41
Lipids and Cardiac Risk
42
Cholesterol Synthesis
Genomic Medicine Cardiovascular Disease New
England Journal of Medicine Volume 349(1) 3 July
2003  pp 60-72
43
Lipid Profile and Cardiac Risk

• Cardiac Risk Factors
• Cholesterol, total
• Triglycerides
• HDL cholesterol
• LDL cholesterol (calculated vs direct)
• NCEP Guidelines ATPIII
• Fasting sample now required for
• Total cholesterol
• HDL-C
• LDL-C
• Triglycerides

44
Cholesterol

• Dependent on many factors
• genetics, age, sex, diet, physical activity,
  hormones
• American Heart Association lt 200 mg/dl
• Measurement
• Enzyme method most common

45
LDL-C

• The villain - directly correlated with CHD
• Carries cholesterol from its site of origin into
  the blood vessels
• Optimal lt100 mg/dL
• Near or above optimal 100-129 mg/dL
• Borderline high 130-159 mg/dL
• High 160 189 mg/dL
• Very high gt 190 mg/dL
• Calculation
• LDL Total Cholesterol - (HDL Triglycerides)
• 5
• Triglycerides gt 400 mg/dL causes problem in
  calculation
• Direct measurement (new)

46
HDL-Cholesterol

• The hero - inversely correlated with CHD
• transfers cholesterol from cells back to the
  liver
• New!! lt45 male lt55 female
• Factors which increase HDL
• estrogen (women), exercise, alcohol, blood
  pressure medicine
• Factors which decrease HDL include
• progesterone, obesity, smoking, triglycerides
  and diabetes
• Measurement
• HDL Precipitation method

47
Non-HDL-C

• Other lipid compounds including
• Lp(a), VLDL remnant are significant in
  individuals with increased triglycerides
• Non HDL-C
• Triglycerides lt200 mg/dL and LDL-Clt100 mg/dL
• Should then look at non-HDL-C
• Total cholesterol HDL

48
Triglycerides

• Role as a risk factor remains unsettled
• Considered an independent risk factor
• Definite association between triglycerides and
  CHD. gt150 mg/dL risk
• While high levels may not cause atherosclerosis,
  they may indirectly accelerate atherogenesis by
  influencing the concentration and composition of
  other lipoproteins
• Measurement - fasting gt 12 hours required

49
Other lipid measurements

• Lp(a)
• similar in structure to LDL
• a unique protein apo(a) linked to apolipoprotein
  B-100 - has a structure similar to plasminogen
• directly correlated with CHD - not affected by
  lifestyle factors such as diet, exercise or
  smoking
• levels gt30 mg/dl
• Apolipoprotein A
• Associated with HDL
• Apolipoprotein B-100
• Associated with LDL

50
Major Risk Factors (Exclusive of LDL Cholesterol)
That Modify LDL Goals

• Cigarette smoking
• Hypertension (blood pressure gt 140/90 mm Hg
• or on antihypertension medicine
• Low HDL cholesterol (lt40 mg/dL)
• Family history of premature CHD
• males first degree relative lt55 years
• Female first degree relative lt 65 years
• Age
• Men gt 45 years
• Women gt 55 years
• Diabetes is regarded as a CHD risk equivalent
• HDL cholesterol gt 60 mg/dL counts as a negative
  risk factor
• Its presence removes 1 risk factor from the total
  count

51
High risk individuals

• Risk for a diabetic is as high as someone with
  existing heart disease
• Other individuals with gt20 risk for heart attack
  in 10 years
• Goal reduce LDL-C to lt100 mg/dL

52
Three Categories of Risk That Modify LDL
Cholesterol Goals
Risk Category LDL Goal (mg/dL) NON-HDL Goal (mg/dL)
CHD and CHD Risk Equivalents lt100 lt130
Multiple (2) risk factors lt130 lt160
0-1 risk factor lt160 lt190
Diabetes counts as a CHD risk equivalent
because it confers a high risk of new CHD within
10 years
53
Metabolic syndrome

• Previously called Syndrome X
• A constellation of risk factors that include
• Abdominal obesity
• Atherogenic dyslipidemia (elevated triglyceride
  concentration, small LDL particles, low HDL-C,
  elevated blood pressure, insulin resistance and
  prothrombotic and proinflammatory states)

54
Clinical ID of Metabolic Syndrome
Risk Factor Defining Level
Waist Circumference
Men gt40 in
Women gt35 in
Triglycerides gt150 mg/dL
HDL cholesterol
Men lt40 mg/dL
Women lt50 mg/dL
Blood Pressure gt 130/gt 85 mmHg
Fasting glucose gt 110 mg/dL
55
Clinical Guidelines

• With new guidelines
• Perform a lipoprotein profile on every adult at
  least every 5 years
• Annual profile on diabetics
• Estimate 1 in 5 individuals will be treated with
  one of the statins (lipid lowering drugs)
• More frequent measurements for those on therapy

56
Lipid Case Study

• Below are the lab results of a 50 yr old male
•  
•      Glucose 75 mg/dL
•      Cholesterol 309 mg/dL
•      Triglycerides 588 mg/dL
•      HDL Chol 23 mg/dL
• Calculate the LDL cholesterol value of this
  patient.
• The direct measurement of LDL Cholesterol is 240
  mg/dL. Is there a discrepancy between the
  measured and calculated LDL result? If so, why?

57
Clinical Chemistry Part 2

• Vicki S. Freeman, Ph.D.

58
Enzymes
59
Objectives

• Discuss the use of enzymes as laboratory aids in
  the following disorders
• Myocardial infarction (LD, CK, AST, LD-1, CKMB)
• Hepatocelluar disease (AST, ALT)
• Hepatobiliary disease ALP, GGT)
• Degenerative bone disease (ALP)
• Pancreatitis (amylase, lipase)
• Prostatic carcinoma (ACP, PSA)
• Dengerative muscle disease

60
Enzymes

• Diagnostic Value
• Found in differing concentrations in tissues
• Cellular damage and/or increased intracellular
  synthesis results in increased serum enzyme
  levels
• Isoenzyme forms of an enzyme may be more specific
  to certain organ systems

61
Clinically Significant Enzymes

• Creatine kinase (CK)
• Lactate dehydrogenase (LD)
• Aspartate transaminase (AST)
• Alanine transaminase (ALT)
• Gamma glutamyltransferase (gGT)
• Alkaline phosphatase (ALP)
• Acid phosphatase (ACP)
• Amylase
• Lipase

62
Creatine Kinase (CK)

• 3 isoenyzmes (MM, MB, BB)
• Found in
• skeletal muscle (CK-MM)
• cardiac muscle (CK-MB)
• brain, nerve, intestine (CK-BB)
• Significance
• Skeletal muscle disease
• Cardiac disease
• Central nervous system

63
Lactate Dehydrogenase

• 5 isoenzymes (LD 1, 2, 3, 4, 5)
• Found in
• skeletal muscle , erythrocytes, cardiac muscle,
  kidney, lung, tumor cells, hepatocellular
• Significance
• LDH-1 (heart) - myocardial infarction, RBC
  diseases, kidney disease, and testicular tumors
• LDH-2 (RE system) - infections
• LDH-3 (lung) lung disease and certain tumors
• LDH-4 (kidney, placenta, and pancreas)-
  pancreatitis
• LDH-5 (liver and striated (skeletal) muscle) -
  liver disease, intestinal problems, and skeletal
  muscle disease and injury
• All LDH isoenzymes - Diffuse disease or injury
  (for example, collagen disease, shock, low blood
  pressure) and advanced solid-tumor cancers

64
Alanine Transaminase (ALT)Aspartate Transminase
(AST)

• Found in
• skeletal muscle
• cardiac muscle
• hepatocellular tissue
• kidney, pancreas, erythrocytes
• Significance
• Liver disease
• Cardiac (AST only)
• Skeletal muscle (AST only)

65
Gamma glutamyltransferase (gGT)

• Found in
• kidney
• hepatobiliary
• tumors
• Significance
• Liver disease (particularly alcoholic cirrhosis)
• Renal disease
• neoplasms or tumors

66
Alkaline Phosphatase

• Found in
• hepatobiliary
• Bone (higher in children)
• placenta
• renal tubules, intestinal
• Significance
• Hepatobiliary disease (particularly obstruction)
• Bone disease

67
Acid Phosphatase

• Found in
• Prostate
• hepatobiliary
• breast tissue
• bone marrow, rbcs, plts, spleen
• Significance
• Prostatic cancer
• bone disease
• vaginal washings in rape investigations

68
Amylase and Lipase

• found in
• Pancreas
• Salivary glands (amylase only)
• Significance
• Pancreatic Disease
• Mumps (amylase only)

69
Cardiac Function

• Acute Coronary Syndromes

70
Objectives

• Discuss the changes in total serum CK, LD, and
  AST after acute myocardial infarction.
• Interpret cardiac markers in patients with
  suspected acute myocardial infarction
• CK and CKMB
• LD and LD-1
• Troponin
• Describe the clinical usefulness of myoglobin,
  troponin and BNP versus CK markers in assessing
  acute myocardial injury.

71
Cardiac Markers

• Myoglobin
• B-type natriuretic peptide (BNP)
• or
• N-terminal pro-BNP (NT-proBNP)
• hsC-Reactive Protein (hsCRP)

• CK isoenzymes
• CK-BB
• CK-MB
• CK-MB isoforms
• CKMB1
• CKMB2
• CK-MM
• Troponin
• complex consists of 3 subunits
• troponin T (cTnT)
• troponin I (cTnI)
• troponin C

72
Cardiac Injury Panel

• Cardiac Injury
• CK-MB
• Troponin (T and I) (The preferred marker!!
• Myoglobin
• Others
• old
• Total CK
• LD/LD1
• AST (SGOT)
• New
• BNP
• hsCRP

73
Myocardial Infarction

• Initial Evaluation
• Assess probability that patients symptoms (i.e.
  chest pain) are related to acute coronary
  ischemia
• Assess the patients risk of recurrent cardiac
  events (including death and recurrent ischemia)
• Cardiac biomarkers should be used in conjunction
  with clinical history, physical exam, ECG
  interpretation

74
Troponin

• Preferred marker for detection of cardiac injury
  and risk stratification
• Has isoforms that are unique to cardiac myocytes
• Fewer false positive results (when concomitant
  with skeletal injury)
• Rises within 3-4 hours after onset
• Remains elevated 10-14 days
• Independent risk factor of death and ischemic
  events in acute coronary syndrome
• 4 fold higher risk of death and recurrent MI in
  patients with an elevated troponin (both T and I)
• Independent of other clinical indicators such as
  age, ST deviation, and presence of heart failure
• Elevated troponin levels are associated with
  likelihood of poor outcomes in angioplasty

75
CK-MB

• CK-MB (by mass spectrometry) is an acceptable
  alternative to troponin
• Perform serial testing
• Upon presentation to hospital
• At at 6-8 hours
• Again at 12-24 hours
• 1-3 of CKMB comes from skeletal muscles
• Begins to rise between 3-6 hours post MI
• Falls to normal levels at 48-72 hours
• Use of the serial measurements useful in the
  management of the MI after diagnosis
• Release of CKMB from cardiac myocytes indicates
  myocardial necrosis
• Use for detection of recurring MIs

76
Myoglobin

• An early marker of myocardial necrosis, if
  performed during first 6 hours of onset of
  symptoms
• High concentration also found in skeletal muscle
• Because of small molecular size, is useful for
  early detection
• Begins to rise 1 hour after onset of myocyte
  damage
• Returns to normal within 12-24 hours

77
Other markers

• Total CK, AST, b-hydroxybutric dehydrogenase, or
  LD should not be used as biomarkers for MI
• These are of low specificity

78
Serum Cardiac Markers

• Cardiac troponin is the preferred marker for the
  diagnosis of MI.
• CK-MB subforms for diagnosis within 6 hrs of MI
  onset
• cTnI and cTnT efficient for late diagnosis of MI
• CK-MB subform plus cardiac-specific troponin best
  combination
• Myoglobin may be added
• as an early marker for MI
• for an early detecxtion of a reinfarction
• CKMB preferred marker for detection of
  re-infarction early after MI
• Do not rely solely on troponins because they
  remain elevated for 7-14 days and compromise
  ability to diagnose recurrent infarction

79
Markers for Risk Stratification

• Troponin - the preferred marker
• hsC-Reactive Protein (CRP)
• B-type natriuretic peptide (BNP) or N-terminal
  prohormone BNP (NT-proBNP)

80
Markers of inflammation

• hs-CRP
• Patients without biochemical evidence of
  myocardial necrosis but who have an elevated
  hsCRP level are at an increased risk of an
  adverse outcome, especially those whose hsCRP
  levels are markedly elevated
• interleukin-6 serum amyloid A - acute phase
  reactant proteins
• Elevated levels have been shown to have a similar
  predictive value of an adverse outcome as CRP

81
BNP (B-type natriuretic peptide)

• Neurohormone synthesized predominantly in
  ventricular myocardium
• Released from cardiac myocytes in response to
  ventricular wall stress
• Strong relationship with mortality in patients
  with unstable angina
• Rises after exercise in patients with coronary
  disease
• Circulating levels of BNP correlate with presence
  and severity of congestive heart failure

82
Troponin and BNP

• a single measurement of B-type natriuretic
  peptide, obtained in the first few days after the
  onset of ischemic symptoms, provides predictive
  information for use in risk stratification across
  the spectrum of acute coronary syndromes (ACS)
• Low mortality rate found for patients with
  negative troponin results and low BNP levels

83
ACC Guidelines (ACC)

• 4 Categories
• Noncardiac diagnosis
• Chronic unstable angina
• Possible ACS (acute coronary syndrome)
• Definite ACS
• Patient Management includes
• Patient history
• 12 lead ECG
• Cardiac Markers - preferrably cardiac-specific
  troponin
• ACC American College of Cardiology

84
Rule of ThumbCriteria for Diagnosis of MI

• Serial increase, then decrease of plasma CK-MB,
  with a change gt25 between any two values
• CKMB gt10-13 U/L or gt5 total CK activity
• Increase in CKMB activity gt50 between any two
  samples, separated by at least 4 hrs
• If only a single sample available, CK-MB
  elevation gttwofold
• Beyond 72 hrs, an elevation of troponin T or I

85
Hepatic Function
86
Objectives

• Identify laboratory tests commonly used to
  diagnose liver disease
• Correlate expected results in pre-hepatic
  (hemolytic jaundice), intrahepatic (hepatitis and
  cirrhosis), and posthepatic (obstructive
  jaundice) related disorders for the following
  tests
• Serum and urine bilirubin (total, conjugated,
  unconjugated)
• Urine and stool urobilinogen
• Enzymes (AST, ALT, Alkaline Phosphatase, GGT)

87
Hemoglobin Breakdown

• The reticuloendothelial cells break down
  hemoglobin into bilirubin
• Hemoglobin
• B
• Verdohemoglobin
• B
• Biliverdin Fe Globin
• B
• Bilirubin
• Albumin B
• Bilirubin - Albumin Complex

88
Bilirubin Conjugation

• The bilirubin-albumin complex is transported by
  the bloodstream to the liver where it is
  conjugated
• Bilirubin-Albumin Complex
• B to the liver
• Bilirubin
• B to parenchymal cells
• Bilirubin UDP-glucuronic
  acid
• B
• Bilirubin diglucuronide

89
Urobilinogen Formation

• Bilirubin diglucuronide is excreted to the
  intestines through the bile ducts where it is
  converted further for excretion
• Bilirubin diglucuronide
• B to intestine
• Converted to urobilinogen by bacterial
  enzymes
• B
• B B
• 50 reabsorbed Rest converted to into
  bloodstream urobilin
• B B
• Reabsorbed by liver Excreted in feces
• or excreted in urine

90
Hepatic Function
91
Prehepatic Jaundice

• Causes
• Hemolytic disease
• Neonatal physiologic
• Lab Findings
• Bilirubin
• Serum A unconjugated Urine Negative
• N - A conjugated
• Urobilinogen
• Stool A levels Urine A levels

92
Hepatic

• Causes
• Conjugation failure due to enzyme deficiency
• Bilirubin transport failure
• Hepatic cell damage
• Lab Findings
• Bilirubin
• Serum A unconjugated Urine Positive
• A conjugated
• Urobilinogen
• Stool Variable Urine Variable

93
Posthepatic Jaundice

• Causes
• Obstruction of the common bile duct
• Lab Findings
• Bilirubin
• Serum A unconjugated Urine Positive
• A conjugated
• Urobilinogen
• Stool B to negative Urine B to negative

94
Liver Function Profile

• Bilirubin (total and direct)
• AST
• ALT
• Alkaline phosphatase
• ?GT

95
Hepatocellular disease

• Damage to the parenchymal cells of the liver
• Laboratory Findings
• A serum bilirubin
• Marked A AST and ALT
• A alkaline phosphatase
• A gamma glutamyltransferase (gGT)

96
Cirrhosis

• Cirrhosis is a condition in which the liver has
  been progressively destroyed through a disease
  process such as primary biliary cirrhosis or
  alcoholism.
• Laboratory Findings
• A bilirubin
• A gamma glutamyltransferase (gGT)
• A alkaline phosphatase
• Mod A AST
• Normal to sl A ALT

97
Biliary Obstruction

• A blockage of the biliary duct usually caused by
  a gallstone or tumor.
• Laboratory Findings
• B to no urobilinogen
• A in conjugated bilirubin
• A markedly alkaline phosphatase
• Mild A in AST and ALT
• A gGT helps differentiate source of ALP

98
Renal Function
99
Clinical ChemistryPart 3

• Vicki S. Freeman

100
Renal Function
101
Objectives

• Renal Function
• Identify laboratory tests commonly used to
  diagnose renal disease
• BUN (urea)
• Creatinine
• Creatinine Clearance
• Ammonia
• Discuss the sensitivity and specificity of serum
  creatinine and BUN as renal function tests.
• Correlate kidney function tests with clinical
  findings in
• Glomerulonephritis
• Nephrotic Syndrome
• Renal tubular acidosis
• Renal failure - acute and chronic
• Renal transplants
• Correlate uric acid values with advanced chronic
  renal failure and gout.

102
Renal Function Profile

• Electrolytes (NA, K, CL,HCO3)
• Anion gap
• BUN and Creatinine
• Creatinine clearance
• Glucose
• Ca, P, and Mg
• Protein and Albumin
• 24 hr urine protein and creatinine

103
Renal Function

• Non-protein Nitrogen Compounds
• Urea (BUN)
• Creatinine
• Ammonia
• Uric Acid

104
Azotemia

• Any significant increase in NPN compounds
  (usually BUN and creatinine) in the blood
• Prerenal
• Renal
• Post renal

105
Blood Urea Nitrogen (BUN)

• Urea H2N-CO-NH2
• end product of NH3 (protein and amino acid)
  metabolism in liver
• 2 molecules of nitrogen per mole of urea
• secreted by the renal tubules at a rate that is
  proportional to the glomerular filtration rate
  (GFR)
• freely filtered by the glomeruli (90 is
  excreted)
• BUN is an indirect measure of urea (convert to
  urea by multiplying by 60/28 or 2.14)

106
BUN - Significance

• Increased in
• Impaired kidney function
• Prerenal azotemia - any cause of reduced blood
  flow
• Post azotemia - any obstruction of the urinary
  tract
• Decreased
• in low protein diet or increased utilization of
  protein
• severe liver disease
• Levels may vary with diet, sythesis in liver and
  amount secreted by kidney

107
Creatinine

• Formed by the muscle from creatine
• Amount proportional to muscle mass, constant
  excretion rate
• Freely excreted by the kidney glomerulus
• Better indicator of glomerular function than BUN
• Less influenced by diet and prerenal and post
  renal factors

108
Creatinine

• Increased due to
• impaired renal function
• 1/2-2/3 of function lost
• Prerenal azotemia
• postrenal azotemia
• Muscle disease
• Decreased in pregnancy
• Serum creatinine levels are a direct reflection
  of muscle mass and show little response to diet

109
BUN/Creatinine Ratio

• Ratio generally between 101 and 201
• Increased ratio indicates
• catabolic states of tissue breakdown
• compromised blood flow
• Decreased ratio indicates
• acute tubular necrosis
• low-protein diet, starvation
• severe liver disease

110
Creatinine Clearance

• Measure both blood and urine creatinine
• Timed collection
• usually 24 hours
• midperiod blood collection
• the volume of plasma that contained creatinine
  excreted into the urine per unit volume (1 min)
  can be calculated
• Significance - indication of glomerular
  filtration rate (GFR) as renal function fails,
  creatinine clearance decreases

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Pathological Conditions
  BUN Creatinine Creatinine Creatinine Ratio
Prerenal ? N N N ?
Caused by reduce blood flow or cardiovascular failure Caused by reduce blood flow or cardiovascular failure Caused by reduce blood flow or cardiovascular failure Caused by reduce blood flow or cardiovascular failure Caused by reduce blood flow or cardiovascular failure Caused by reduce blood flow or cardiovascular failure
Renal ? ? ? ? ? - N ? - N
Caused by diseases affecting the glomerulus or tubule function Caused by diseases affecting the glomerulus or tubule function Caused by diseases affecting the glomerulus or tubule function Caused by diseases affecting the glomerulus or tubule function Caused by diseases affecting the glomerulus or tubule function Caused by diseases affecting the glomerulus or tubule function
Postrenal ? ? ? ? - N ? - N ? - N
Caused by obstruction of urine flow Caused by obstruction of urine flow Caused by obstruction of urine flow Caused by obstruction of urine flow Caused by obstruction of urine flow Caused by obstruction of urine flow
112
Uric Acid

• End product of purine (nucleic acid) metabolism
• Serum uric acid depends on
• purine synthesis and metabolism
• dietary intake and metabolism
• renal function
• Increased uric acid seen in
• gout
• increased cell turnover
• renal impairment
• Uric acid is very insoluble and can form kidney
  stones

113
Pathological Conditions
  BUN Creatinine Proteinuria
Acute glomerulonephritis ? ?
Nephrotic syndrome N N
Tubular disease N N
Acute Renal Failure ? ?
114
Renal Tubular Function Tests

• Measures the concentrating and diluting ability
  of the renal tubules
• Osmolality
• Measure of of moles of particles/kg water
• Impairment of renal concentrating ability is an
  early manifestation of chronic renal disease
• Specific gravity
• ratio of weight in grams/ml of body fluid
  compared to water

115
Electrolytes
116
Objectives

• Electrolytes and Acid-base Balance
• Identify the major electrolytes found in the body
  and the relative distribution of each.
• Calculate an anion gap given a set of electrolyte
  values.
• Describe the use of a measured and calculated
  osmolality result.
• Calculate an osmolality given a set of laboratory
  results.
• Identity the normal HCO3/H2CO3,
• Describe the laboratory parameters (pH, pCO2, and
  HCO3) for the following acid/base disorders
• Respiratory acidosis
• Respiratory alkalosis
• Metabolic acidosis
• Metabolic alkalosis

117
Electrolytes

• Cations -
• positively charged ions
• includes major electrolytes
• Na Ca
• K Mg
• Trace elements
• Cu Fe Mn Li
• Zn Co Br

118
Electrolytes

• Anions
• Negatively charged ions
• Includes major electrolytes
• Cl- HPO4--
• HCO2- SO4--
• Trace elements
• I-
• Fl-

119
Electrolytes

• Extracellular
• Na - Major cation
• Cl - Major anion
• Intracellular
• K - major cation
• Others - Mg

120
Sodium Major extracellular cation

• Na levels are controlled by renal tubular
  function and somewhat by aldosterone
  (adrenocortical hormone from renin-angiotensin
  system)
• Relates to plasma osmolality (2x Na
  osmolality)
• Hypernatremia hypotonic dehydration, renal
  failure, lack of ADH, hyperaldosteronism, etc.
• Hyponatremia over-hydration, renal tubular
  dysfunction, hypoaldosteronism

121
Potassium main intracellular cation

• K levels controlled by renal tubular secretion/
  reabsorption and affected by aldosterone
  (inversely with Na), acid-base balance and
  glucose transport under insulin influence.
• Plasma K falsely increased in hemolysis.
• K levels fall after insulin administered to
  control hyperglycemia.
• K and H levels often correlate.
• Hyperkalemia due to renal failure, ketoacidosis,
  hypoaldosteronism.
• Hypokalemia in renal tubular defects,
  hyperaldosteronism, dietary deficiencies (esp.
  when taking diuretics or laxatives), severe
  vomiting

122
Chloride main extracellular anion

• Cl- is controlled by renal function with
  aldosterone influence on tubular secretion (Na
  and Cl- are reabsorbed as K and H secreted) in
  response to aldosterone.
• Hyperchloremia may be due to dehydration, severe
  hyperaldosteronism, renal failure, diabetes
  insipidus, etc. Hypochloremia is found in
  overhydration, severe vomiting, renal tubular
  dysfunction, severe hypoaldosteronism

123
Total CO2 and Bicarbonate

• CO2 (and HCO3-) is controlled by renal tubular
  function based on plasma pH. It buffers H
  produced in metabolic functions or control
  acid-base disturbances.
• Increased HCO3- is due to metabolic alkalosis
  (vomiting, hypokalemia, overtreatment with
  bicarbonate) or to compensate respiratory
  acidosis (from hypercapnia and pulmonary
  diseases).
• Decreased HCO3- is due to metabolic acidosis
  (from organic acid production, severe diarrhea,
  renal tubular acidosis or renal failure) or to
  help compensate for respiratory alkalosis in
  hypo-ventilation and hypocapnia

124
Anion gap

• Anion gap Na - (Cl CO2)
• Normal range 8 - 16
• Gap due to excess unmeasured anions
• HPO4-- SO4--
• organic and lactic acids
• Increased anion gap usually due to decreased
  anions, especially CO2 as in metabolic acidosis
  from lactate, ketones, organic acid poisoning,
  uremia.
• Decreased anion gap is rarely due to pathologic
  problem (such as increased proteins in myeloma),
  almost always technical problem with instrument.

125
Case of Electrolyte Imbalance

• Case 333333 15 year old non-responsive
  diabetic female with gastrointestinal virus over
  past few days has the following results
• Na 144 Glucose 250 mg/dl
• K 4.5 Lactate 5 (0.5-2.2)
• Cl 98 Osmolality 312 (275-295)
• CO2 15 Urea N 35 (6-20)
• Controls were accepted for all analysis. CO2
  results from earlier and subsequent patient
  samples were relatively normal.

126
Osmolality

• Measure of colligative properties
• properties that are directly affected by of
  solute particles per mass of solvent
• Major contributions to plasma osmolality are Na,
  Glucose, BUN and unmeasured organic substances
  such as ethanol, methanol.
• Osmolality units are mOsmole/Kg (plasma H2O).

127
Osmolality

• Can be measured or calculated
• 1.86 (Na) Glucose BUN 9
• 18 2.8
• Increased in
• Diabetes, renal disorders
• Decreased in
• Lymphomas, shock, MI
• Osmolality gap
• measured osmolality - calculated osmolality
• normal lt 10

128
Hyperosmolar Coma

• Hyperglycemic, hyperosmolar, nonketonic
• Due to a combination of severe dehydration caused
  by inadequate fluid intake and insulin deficiency
• Characterized by
• Blood glucose above 600 mg/dl
• N - sl decreased pH
• Serum osmolality above 350 mOsm/kg
• Lethargy or coma
• BUN increased

129
Osmolality

• Measurement by
• Freezing point depression
• Vapor pressure increase
• boiling point increase
• osmotic pressure increase
• Osmolal gap
• measured osmo minus calculated osmo
• Gap increased in
• ketoacidosis renal tubular acidosis
• lactic acidosis methanol, etc. poisonings

130
Acid Base Balance
131
Acid/Base Balance

• pH
• pCO2
• HCO3
• pO2
• pH and HCO3- are directly related
• pH and pCO2 are inversely related
• Balance is maintained by ratio

132
Relationships

• Normally measured
• Total CO2
• pCO2
• Mathematical Conversions
• H2CO3 pCO2 x 0.03
• Total CO2 - HCO3- H2CO3
• Henderson/Hasselbach Equation
• pH pKa log HCO3-
• H2CO3

133
Acid Base Components

• HCO3-
• metabolic component
• Total CO2 (from electrolyte report in mMole/L)
  relates closely to HCO3-
• H2CO3
• respiratory component
• pCO2 is measured value relating to H2CO3 pCO2 x
  0.031.
• Neither HCO3- nor H2CO3 is directly measured

134
Classifying Acid Base Balance

• Low pH acidosis High pH alkalosis
• Compare HCO3- to pH to determine metabolic
  (should be directly related)
• Compare pCO2 to pH to determine respiratory
  (should be inversely related)
• Look for compensation.

135
Compensation

• Compensation begins with the unaffected component
  from the HCO3-/ H2CO3 ratio.
• Compensation is evident when both values in the
  ratio are increased or decreased and pH is moving
  towards normal

136
Acid-Base Disorders
137
Case Study

• A patient has the following results blood gas
  results
• Patient Reference Range
• pH 7.33 (7.35-7.45)
• pCO2 65 mm Hg (35-45)
• tCO2 35 mM/L (25-33)
• What is the likely acid-base status?

138
Parathyroid Function

• and Calcium Metabolism

139
Objectives

• Parathyroid Function and Calcium Metabolism
• Using PTH and calcium assay results,
  differentiate between
• Hypoparathyroidism (primary vs secondary)
• Hyperparathyrodism (primary vs secondary)
• Vitamin D levels
• Correlate serum alkaline phosphatase (ALP) with
  bone disorders.
• Thyroid Function
• Using T3, T4 and TSH levels, differentiate
  between
• Hyperthyroidism (primary, secondary and tertiary)
• Hypothyroidism (primary, secondary and tertiary)
• Describe the factors that affect thyroid binding
  globulin levels.

140
Minor Electrolytes/Minerals

• Physiologic Control of Calcium and Phosphorus
• Parathyroid Hormone Secretion in response to low
  plasma Ca by 4-6 glands in larynx region
• Maintains homeostasis but increased level will
  increase serum calcium and urinary phosphorus and
  decrease serum phosphorus.
• Vitamin D increases calcium levels.
• Calcitonin counters PTH effect on bone.

141
Physiologic Control of Minerals

• PTH causes
• bone resorption (breakdown)
• renal reabsorption (into bloodstream)
• intestinal absorption of calcium
• renal secretion of phosphorus into urine.

142
Parathyroid Function
143
Thyroid Function
144
Thyroid Function

• Primary
• Secondary
• Tertiary

145
Thyroid Function
146
Thyroid Testing
Sensitive TSH (mU/L)
lt0.3
0.3 - 5.0
gt5.0
FT4
Normal
Microsomal
No further test
antibody
and FT4
T3 if FT4
normal
3rd generation
TSH if sTSH
lt0.1 mU/L
147
Thyroid Function

• Thyroid-binding globulin
• increased in
• estrogen
• pregnancy
• oral contraceptives
• decreased in
• androgens
• malnutrition
• liver disease

148
Tumor Markers

• Screen in healthy or asymptomatic population low
  false positive, low false negative rate
  specificity and sensitivity issues
• Example colorectal cancer screen with fecal
  occult blood
• Monitoring in symptomatic patients for diagnosis,
  follow-up to treatment most tumor markers fit in
  this category

149
Diagnostic Relevance/Medical Decision Levels for
Clinical Sig.

• Diagnostic Specificity Absence of Tumors
  (disease)
• Negative Predictive Value
• of patients with negative tumor marker (below
  the cut-off point) who dont have the tumor
• Specificity relates to of true negatives
• Diagnostic Sensitivity Presence of Tumors
  (disease)
• Positive Predictive Value
• of patients with positive tumor marker (above
  the cut-off point) who do have the tumor
• Sensitivity relates to of true positives

150
Tumor Markers

• PSA in conjunction with digital rectal exam
• Fecal occult blood with colonoscopy
• Ca-15-3 with mammography