Interpretation of

Clinical Laboratory Tests

Michael P. Peppers, Pharm.D.
Pharmacy Manager, St. Louis Branch

Learning Objectives
 Discuss the importance of  List 3 class of drugs that require
– When to draw labs periodic drug level monitoring
– What a “Normal Lab Value” means – To minimize adverse reactions
– What an “Abnormal Lab Value” means – To maximize effectiveness.
– Potential for error in
 Laboratory test values
 List one frequently monitored test
 Units of measure value for
 Timing – Asthma
 Technique in drawing – Congestive heart failure
 Discuss the differences in chemistry – Diabetes
profiles
fil – Cancer.
– BMP (SMA-6, Basic Metabolic Profile)
– Chem Panel-12 (SMA-12)
– CMP (Complete Metabolic Profile, Chem
Profile-20)
– Renal Panel
– Critical Care Panel
– Cost/benefit issues.

Interpretation of Clinical Laboratory Tests date

What is a Blood test?

 An essential diagnostic tool that reveals details about:

– Blood cells
– Blood components
– Fluids and Electrolytes
– Electrolytes
– N tritional status
Nutritional stat s
– Body organ function
– Acid-base status
– Immune function
– Compliance with medication regimens

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 Blood Components

 Plasma (semi-solid component)

– Plasma Albumin, immunoglobulin, coagulation factors, protein C and S,
fibrinogen, antithrombin, platelets, etc.
– Turns into a solid when clotting cascade activated

 Serum (liquid component)

– Disolved components, drugs, electrolytes, gases, etc.
– Serum, The remaining liquid, which can be used in blood tests to assist
in determing how various body organs may be functioning

Interpretation of Clinical Laboratory Tests date

When should we actually draw a blood test?

 Suspicion leads the clinician to believe there is a medical problem
– Infectious diseases (CBC/Differential; Legionella titers, Tularemia, etc.)
– VTE / Pulmonary embolism (D-Dimer)
– Adrenal Insufficiency (Serum Cortisol pre and post Cosyntropin Injection)
– Hypo / Hyperthyroidism (Cardiac Arrhythmias, Fatigue, FUO, etc.)
– Systemic Lupus Erythematosus
– Inflammatory Conditions (CRP, ESR)
– And ON….and ON….and ON.
– BASICALLY To ASSIST in confirmation of diagnosis

 To follow up on prescribed therapy

– Serum Drug Levels (gentamicin, vancomycin, digoxin, theophylline, thiocyanate)
– Hemoglobin A1-C (HgA1C)
– Prostate Specific Antigen (PSA)
– Culture and Sensitivities (C&S)
– Carcinoembrionic Antigen (CEA)

 Should NOT draw lab test if nothing is going to be acted upon

Interpretation of Clinical Laboratory Tests date

Common conditions for acquiring blood lab tests

 Allergies  Nutritional status

 Autoimmune Diseases  Gastrointestinal Diseases
 Blood Cholesterol  Heart Health
 Diabetes  Hormones and Metabolism
 DNA, Paternity and Genetic  Infectious Disease
Testing
 Kidney Disease
 Drug Screening
 Liver Diseases
 Environmental Toxin
 Sexually Transmitted Diseases
 Thyroid Disease

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Overview

 Specialized lab tests

 Specific disease states
 Specific drug therapy
 Implications for case management

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General Principles
 Serum, blood, urine, CSF other fluids
– Screening
 Qualitative
 Urine drug screens
 Example (urine drug screen obtunded teenage girl  opiates)
– Diagnostic
 Quantitative
 Serum drug levels
 Example (serum Fentanyl Level 5 mcg/ml in same teenage girl, 2 days post
presentation to ICU with no narcotics given in past 2 days  DATE RAPED with
fentanyl disk)
 Cost vs benefit
– Benefit must outweigh the cost or danger of procedure
 Every blood stick introduces chance for infection
 Daily blood sticks or multiple blood draws throughout therapy may lead to anemia
such as seen in the ICU or in the chronic dialysis patient (multiple blood draws do
contribute to some of the anemia in dialysis patients due to their lack of erythropoetin
in regenerating substrate)
– Outcome must affect decisions in therapeutic management
 BNP greater than 400 in acutely decompensated CHF patient  NATRECOR
treatment (expensive drug, but will keep patient out of ICU)

Interpretation of Clinical Laboratory Tests date

General Principles: Normal Values

 “Normal Range”  Variations among labs
– Defined by healthy population
– Vary widely within age groups, weight
– Use norms listed by lab, keep in mind
groups, sex, feeding status that there are three blood test "normal
– THUS, normal is only normal in the ranges."
bell curve of a population
– REMEMBER….there is NOT
 Personal Norms
NORMAL serum drug level…only – Just like temperature, all have
therapeutic, subtherapeutic and toxic individual normals
ranges.
– Pediatric values are different than – High normal may be extreme high in
adult values some p patients ((example:
p WBC 10,000
,
may be normal in most, but someone
 Variations do exist who normally runs 4,000, this could
be signs of serious infection)
– Age, Sex, wt, ht, food, drug-effect,
diseases, etc.
 Serum creatinine is a fantastic
 Be sure to review the individual
example of how one can labs reference points for normal
MISINTERPRET renal function in the
eldery ranges when assessing
 Renal Dysfunction, pregnancy and
neonate are fantastic examples of
how one can MISINTERPRET serum
digoxin levels
 Personal Norms

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Lab Error
 Specimen problem  Medications
– hemolyzed blood
 Hyperkalemia, hyperphosphatemia. – Pseudoephedrine or Conserta
– Lipemic Serum showing up as illicit amphetamines
 Pseudo-hyponatremia
– CPK enzymes in patient lying on floor
 Incomplete
too long – Not enough serum for the procedure
 Wrong time  Technical errors, procedures,
– Vancomycin / Gentamicin Peak /
Trough reagents
 Frequently
q y misinterpreted
p as too low – Decimal place errors when reporting
or too high due to improper timing
– Acetaminophen Toxicity – Wrong patient name on vial
 False interpretation if drawn too soon – Drawing Nutrition support labs or
or too late
– Digoxin Level
serum drug levels out of the same
 12 hours to distribute into tissues / port into which the drug/TPN is being
false high if drawn too soon administered
– Not waiting long enough post fatty
meal to perform BS, Triglycerides,  Diet
Cholesterol levels

Interpretation of Clinical Laboratory Tests date

Units of Measure

 Conventional units
 SI units
 Example:
Conventional glucose SI unit glucose
70-110 mg/dL 3 9 - 6.1
3.9 6 1 mmol/L

Be sure to note which units are being referred to when reading

journal articles about diseases and therapy. USA and other
countries do not always follow same reporting structure.

Interpretation of Clinical Laboratory Tests date

Blood Chemistry
 BMP (Basic Metabolic Panel, SMA-6)
– analyzes Na, K, Cl, CO2, BUN, glucose
– insights into serum electrolytes, acid-base status, renal function and
metabolic state

 Chem Panel-12 (SMA-12)

– add: albumin, total protein, bilirubin, alk phos, calcium and creatinine
– more specific renal evaluation, and liver function, nutritional parameters
– Missing for Nutritional needs is Mg, PO4, Pre Pre-Albumin,
Albumin, Triglycerides

 Chem Profile-20 (CMP)

– Add: phosphorus, cholesterol, triglycerides, uric acid, iron, lactate
dehydrogenase (LD), aspartate aminotransferase (AST), and alanine
aminotransferase (ALT)
– Additional metabolic information, cardiovascular risk, and liver function
– Missing is MAGNESIUM

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Blood Chemistry (cont.)

 Magnesium and Phosphate

– Very important electrolytes that are frequently missing in basic panels
– Both cause problems in managing other electrolytes if not assessed
appropriately

 Magnesium
– Catalyst for the Na-K-ATP Pump

 Phosphate
– Vital component in all enzyme actions and the ATP Pump

Interpretation of Clinical Laboratory Tests date

Blood Gases and Acid-Base

 Critical Care Panel

– ABG (arterial blood gas: pCO2, pO2, pH, HCO3)
– Ionized Calcium
– Magnesium
– BMP (Na, K, Cl, CO2, BS, BUN, Creatinine)
 Very important to interpret all the above in concert
– IIncreased H  Acidemia
d pH A id i  expectt higher
hi h ththan norm K
– Decreased pH  Alkalemia  expect lower than norm K
 pH, pCO2, pO2
 Ventilator management, toxicology management, critical care
management, COPD management, DKA management, etc…

Interpretation of Clinical Laboratory Tests date

Hematology and Coagulation

 RBC, hematocrit (Hct),  Platelets
hemoglobin (Hgb), MCH, MCV, – Thrombocytopenia  idiopathic?
MCHC
– Thrombocytopenia  drug induced?
– Anemias
– Macrocytic  ESR
– Microcytic – Inflamation vs not?
– Do we use IRON or do we use – Allergic reaction?
FOLIC ACID / B-12 or do we use  PT, aPTT, fibrinogen
Erythropoetin or do we combine
allll th
the above?
b ? – Therapeutic drug ?
– Acute onset vs chronic onset? – Liver function ?
– Do we transfuse or not? – Disseminated intravascular
coagulation?
 WBC/differential – How to stop the bleed ?
– Bacterial vs Viral
– Drug-Induced adverse effect

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Therapeutic Drug Monitoring

 Infectious Disease: aminoglycosides (amikacin, gentamicin,

tobramycin), vancomycin
 Pulmonology: aminophylline, theophylline
 Cardiology: lidocaine, procainamide, propranolol, quinidine, digoxin,
digitoxin, BNP, thiocyanate
 Neurology: carbamazepine, phenobarbital, phenytoin, antiepileptics in
gerneral
 Psychiatry: valproic acid

Interpretation of Clinical Laboratory Tests date

Drug Levels
 Clinical importance
– Maintain safest parameter for best therapeutic outcome

 Influenced by many factors

– Compliance,
– Interaction,
– Demographics,
– Clinical condition,
condition
– Timing of administration/collection)

 NO NORMAL levels in human body, thus each person may be affected

slightly different than another
– Digoxin is prime example
– 2 % of population will be toxic within therapeutic range

Interpretation of Clinical Laboratory Tests date

Drug Levels (cont.)

 Peak level  Toxic Range
– highest concentration detected – Levels above which the toxic effects
between doses, within the post manifest quite often
distribution phase
 Toxic effects from commonly
 Trough level monitored drugs
– Lowest level detected prior to – Antibiotics
next dose – Bronchodilators
 Sub-Therapeutic
p Range
g – Anticonvulsants
– Level below which no therapeutic – Cardiac glycosides
effects will be seen
 Evaluate in conjunction with
 Therapeutic Range Renal function, Hepatic Function,
– lowest level of effectiveness Cardiac Function, Hydration
extending to the highest level of status, Patient signs/symptoms
effectiveness without toxicity

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Disease States—Frequently Monitored Values

 Indicate effectiveness of therapeutic regimen

 Current status and underlying disease state evaluation

 Commonly used indicators for:

– diabetes
– CHF
– asthma
– cancer
– nutrition

Interpretation of Clinical Laboratory Tests date

Diabetes

 Blood glucose
 Acid/base
 Glycosylated hemoglobin (HgbA1C)

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Diabetes—Criteria for Admission

 DKA: blood glucose >250mg/dL (>13.9mmol/L) and

– venous pH <7.3 or serum bicarb level <15 MEq/l
– ketonuria and/or ketonemia
 Uncontrolled diabetes
 Hyperglycemia with volume depletion
– recurring blood glucose >300 mg/dL
– recurring episodes of hypoglycemia, or unstable hyper- and hypoglycemic
episodes

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Diabetes—Ongoing Assessment

 Blood glucose
– trends information (daily basis) for adjustments in therapy regimen

 Glycosylated hemoglobin (HgbA1C)

– predicts risk for development of chronic complications
– measured every 3 months
– goal: <7%, reevaluate treatment regimen if >8%

Interpretation of Clinical Laboratory Tests date

Asthma
 Peak flow
– PEF based on “personal best” established over 2-3 weeks of
measurement
– PEF < 80% indicates need for additional meds
– PEF <50% indicates a severe asthma exacerbation

 Drugs:
– routine monitoring of serum theophylline is important in long-term
control
t l
– zileuton (leukotriene modifier), monitor hepatic enzymes (ALT)

 IgE level:
– Allergic asthma
– Rx: Omalizumab

Interpretation of Clinical Laboratory Tests date

Congestive Heart Failure

 Drug levels (e.g. digoxin)
– Critical following the addition of amiodarone
– Critical following decrease in renal function
– Critical as patient ages and renal function declines
 BNP: also known as: b-type natriuretic peptide, proBNP
– Greater than 400 may suggest possible decompensated CHF and need for
niseritide (Natrecor)
 Fluid/electrolyte BUN
Fluid/electrolyte, BUN, creatinine
creatinine, BUN:Cr ratio,
ratio Mg
– Frequent cause of hyponatremia (SIADH), prerenal azotemia and dysfunction,
electrolyte loss due to diuretic and natriuretic therapy
 Anticoagulant labs (INR) as appropriate
– concomitant atrial fibrillation (INR 2-3 x control)
– history of embolism (INR 2-3.8 x control)

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Cancer
 CBC, platelets
– Chemotherapy knocks out fast growing cells, including WBC, Platelets
– Knowing the NADIR of the chemo regimen assists in determining when to
cycle up again or if Hematopoetic stimulation should take place with
medication
 CEA (carcinoembryonic antigen)
– <2.5-10 ng/mL
– Generally detected in Gastrointestinal Cancers, but other cancers show
positive levels
– Elevated in presence of benign or malignant diseases
– Sequential levels are helpful in following patients with tumor
– Are elevated shortly after chemo or radiation therapy due to debulking tumor
and release of antigen
 ANC Absolute Neutrophil Count (Rx marker)
 PSA (prostate-specific antigen)
– Benign prostatic hypertrophy
– Prostatic cancer
– Normal range differs in age groups  increases as age increases

Interpretation of Clinical Laboratory Tests date

Nutritional Status
 Albumin (required level Medicare TPN)
 Pre-Albumin
 Total Protein
 TIBC
 Total lymphocyte count (% of WBC)
 HBG/Hct
 Electrolytes
y
 Triglycerides
 Blood Sugar
 Serum bicarbonate
 LFT
 Pulmonary function tests

Interpretation of Clinical Laboratory Tests date

Case Management Implications

 Are necessary lab values ordered by the physician?

 Are medications adjusted according to lab values?
 Are tests being ordered unnecessarily?
 Are tests being used to monitor underlying disease states?
 Providers should document information and pass on to the case
manager as requested.

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 Questions?
1. T/F? Routine tests of serum, urine and other body fluids should be
performed when assessment of those values will affect decisions in
therapeutic management.

2. T/F? Normal lab values vary from one lab to another, for
consistency, use the reference values from the lab performing the
tests.

3. T/F? Drug classifications that require periodic monitoring for

therapeutic effectiveness include aminoglycosides, bronchodilators,
anticonvulsants
ti l t andd cardiac
di glycosides.
l id

4. T/F? Sequentially elevated CEA levels in a patient with a history of

cancer may indicate increased tumor activity.

5. T/F? A glycosylated hemoglobin level of 6.8% indicates adequate

blood glucose control in a diabetic patient.

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Thank You!!

Questions?

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