Understanding Your Lab Results

Terry Watnick, M.D. Division of Nephrology

The University of Maryland School of Medicine Baltimore, Maryland

What you will Learn today: • Lab Results-The Basics • CBC: Complete Blood Count • “Kidney Labs” Basic Metabolic Panel • “Bone” Labs • Liver Function Studies • Lipid Profile

Why Should you Understand your Lab Results?

• Many Decisions that your health provider makes are based on your lab tests – Establishing a diagnosis – Developing a course of action for treatment – Monitoring response to therapy

What is in Blood?

• WBC: Cells that fight foreign bodies, infection

• RBC: Cells that carry oxygen • Plasma: Contains clotting factors,

fibrinogen • Serum: The part that remains after

fibrinogen is removed & blood clots – Water w/Dissolved proteins (hormones) – Minerals, C02, electrolytes

Example Lab Report

http://labtestsonline.org/assets/static-pages/SampleReport.html

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“Panic Values”

Critical Results or those that are dangerously abnormal must be reported to the responsible person and the lab usually makes note of that

What is meant by the Reference Range? • Normal range vs. Reference Range

– Established by testing a large population of healthy individuals. There is usually a range of “normal”.

– Medical data must be interpreted in context. – For example Avg. heart rate is 70, but in a runner 55 may be ok.

• Reference range interpreted in the context of the reference population.

– Reference Range may vary with Age, for example Alkaline Phosphatase made by bone is higher in kids.

– Reference Range may with Sex, for example creatinine tends to be higher in males

What does it mean if my value is out of the Ref. Range? • Statistical Variability-same sample, ~5% may fall outside the

normal range by chance. • Biological Variability, may vary day to day. • Individual Variability: What is normal? HOWEVER values out of the Ref. Range: • May be significant or indicate a problem that warrants further

investigation. • Analyzed in context of your symptoms, physical exam etc • May need to be repeated:

• For the reasons above. • sample wasn’t collected properly ie not refrigerated, RBC not

separated from serum.

Lab Results must be interpreted in Context by your Health Care Provider

The Complete Blood Count or “CBC”

CBC: Complete Blood Count-I

• Evaluates 3 cell types that circulate in the blood: – WBC (white blood cells) – RBC (red blood cells) – Platelets

• Screens for wide variety of conditions – Infection – Anemia – Inflammation – Bleeding Disorder

CBC: Complete Blood Count-II

• WBC (ref range: 4-11K) – Fight Infection, WBC goes up

when there is a bacterial infection – Differential: Major types of WBC:

neutrophils, lymphocytes – Each type of WBC plays a different

role in the body and the numbers give information about the immune system

• Ex. Eosinophils allergic reactions

CBC: Complete Blood Count-III • Red Blood Cell Count (RBC, ref range 4.1-5.6)

– RBC carry oxygen from the lungs, CO2 from body to lungs • Hemoglobin (12.5-17) is the protein in RBC that carries 02 • Hematocrit (packed cell volume, ref. 36-50%)

– Volume of blood taken up by red cells

• Hemoglobin /Hematocrit are best measures of Anemia • Red Cell Indices

– Mean corpuscular volume (MCV) – Mean corpuscular hemoglobin (MCH) – Mean Corpuscular hemoglobin concentration (MCHC)

• Platelets ( ref range 140K-415K), required for clotting – Too few can cause bleeding, too many clotting

WBC • Decrease

– Bone marrow, disorders or damage

– Autoimmune (SLE), diseases of immune system, HIV

– Sepsis -overwhelming infection – Cancer that spreads to the

bone marrow • Increase

– Infection, bacterial or viral – Inflammation – Leukemia – Severe Stress – Steroids

Platelet • Decrease

(thrombocytopenia) – Viral infection, hepatitis, mono – Platelet autoantibody,

autoimmune – Cirrhosis – Sepsis – Leukemia, other bone marrow

disorders – Chemo, XRT

• Increase – Malignancy – Iron deficiency – RA, SLE, IBD – Essential thrombocytosis

Many Causes of Anemia • Acute or Chronic Bleeding • Nutritional Deficiencies: Iron,

B12, folate • Inherited: sickle cell,

thalassemia • Bone marrow disorders • Chronic Inflammation: lupus,

infection • Viral: hepatitis, HIV • Any Chronic Disease-renal

failure • Drugs: chemotherapy

Polycythemia • Dehydration • Lung Disease, smoking

emphysema • Tumors that produce extra

EPO • Polycythemia Vera

Anemia in Renal Disease • Low RBC/low hemoglobin/low

hematocrit=anemia – Red blood cells carry oxygen to tissues

• Anemia is common in renal disease – Can occur early: 20-50% function remains – Kidneys make erythropoietin (EPO),

stimulates bone marrow – Diseased kidneys don’t make enough EPO

• Treatment – Recombinant EPO, subcutaneously, may

also need iron – Target hemoglobin 10-12, must be

monitored

Functions of the Kidney • Two kidneys, either side of spine. • Each Kidney: 1 million nephrons.

– Nephron filters/processes blood to form urine.

• Regulates the amount of fluid and electrolytes: potassium, calcium & magnesium.

• Waste products ie creatinine are also filtered.

• Kidneys produces 3 hormones: – Erythropoietin, ensures that red blood cells

are produced. – Renin, regulates blood pressure. – Active form of Vitamin ensures calcium is

absorbed from food that we eat.

http://www.nlm.nih.gov/medlineplus/ency/imagepages/19615.htm

Basic/Comprehensive Metabolic Panel

Electrolytes (Na+, K+, Cl-, HC03-)

• Electrolyte Levels are Affected by – How much you take in. – The amount of water in your body. – How much you excrete: The kidney is critical in regulating

how you excrete electrolytes. – You can also lose electrolytes in stool and sweat. – Aldosterone, a hormone produced by the adrenal gland

promotes sodium reabsorption, potassium and hydrogen ion excretion by the kidney.

Sodium, Na+ (ref range: 135-145) • Major positive ion in fluid outside of cells • Brain, muscles, nervous system depend on electrical signals

– Movement of Na+ is critical for electrical signals. – Too much or too little causes cells to malfunction. – Extremes in Na+ levels (too much or too little) can be fatal.

• Excess Na+ such as that in the diet is excreted by the kidneys – Na+ regulates the total amount of fluid in the body.

• Low Na+ or Hyponatremia – Excess water in relation to Na+. – Diseases of the liver, cirrhosis or congestive heart failure. – Excess water drinking.

• High Na+ or Hypernatremia – Excess Na+ in relation to water. – Too little water intake, Loss of water ie vomiting or diarrhea.

Giebisch G, et al, Kidney Int 72: 397-410, 2007

Potassium (ref range: 3.5-5 meq/L)

• Major positive ion inside cells. • Potassium is found in many foods. • Potassium is mostly excreted by

the kidney (~90%). • Potassium is excreted by the GI

tract ~10% under normal conditions.

• Small amount in Sweat. • Aldosterone is a hormone made

by the adrenal gland that is very important in regulating K+ excretion by the kidney.

10%

90%

Why is the Potassium level important? • Proper level is important for normal cell function

– Regulates heart beat and muscle function • Serious Increase aka hyperkalemia or Serious decrease aka

hypokalemia – Increase the chance of irregular heart beat that can be fatal

• The Kidney is critical for getting rid of excess potassium – Small amounts in stool and sweat

• If it is <3.5……………………………You are in the Low Zone If it is 3.5-5.0………………………You are in the SAFE zoneIf it is 5.1-6.0………………………You are in the CAUTION zoneIf it is higher than 6.0……………..You are in the DANGER zone

Abnormal Potassium Too High • Increased Intake, supplements • Kidney Failure • Acid level high • Tissue Trauma

– rhabdomyolysis-muscle breakdown

• Not Enough Aldosterone – Adrenal Failure

• Drugs – Angiotensin-converting enzyme

inhibitors “ACE” – Certain Diuretics (aldactone,

triamterene) – Bactrim

Too Low • Poor Intake • Loss from GI tract

– Vomiting, diarrhea – Excessive laxative use

• Diuretics – HCTZ, Lasix

• Excess aldosterone • Excessive Sweating

Other Electrolytes: Chloride/Bicarbonate Chloride: Cl-

• Ordered with other electrolytes as part of a panel.

• Helps in the diagnosis of other electrolyte abnormalities.

• Can be high in dehydration. • Can be high when too much

bicarbonate is lost. – Can be elevated with

diarrhea

Bicarbonate: or total C02 • Reflects Acid-Base Balance • Bicarbonate= Acid low

– Severe vomiting – Lung Disease (emphysema) – Severe Dehydration – Increased Aldosterone

• Bicarbonate = Acid High – Renal failure (Can’t excrete) – Diabetic ketoacidosis – Chronic diarrhea – Salicylate, methanol, ethylene

glycol – Decreased aldosterone

Basic/Comprehensive Metabolic Panel

What is Glomerular Filtration Rate or GFR? • How well the kidneys are

working: The volume of filtrate produced per minute.

• Normally Kidneys filter 180 Liters of blood per day.

• Only 1-2 Liters of urine. • 99% reabsorbed into blood. • Composition of urine

modified by secretion/reabsorption.

How do we determine Renal Function or GFR? In Clinical Practice the plasma concentrations of waste substances such as creatinine and urea (BUN) are used to estimate renal function.

Measurements of Renal Function, BUN

• Blood Urea Nitrogen or BUN (Reference Range: 6-24). • Urea is produced in the liver when protein is broken

down to amino acids. • Urea released into the blood where it is filtered and

excreted by the kidneys. • Conditions that affect the kidneys and or liver can affect

the amount of urea in the blood. • A High BUN implies impaired Kidney function

BUT BUN can be elevated for reasons other than kidney damage

– Any condition that results in decreased blood flow to the kidneys such as congestive heart failure.

– Severe Dehydration – GI bleeding – Increased Catabolism or protein breakdown

• Increased Protein in the diet • Steroids such as prednisone

– Low BUN not usually a cause for concern can be seen in severe liver disease or malnutrition

Other Measurements of Renal Function

• Creatinine is the best measure of renal function: – Reference range: 0.7 to 1.3 mg/dL for men and 0.6

to 1.1 for women • Muscular young adults may have more, elderly less

– Produced continuously from muscle breakdown – Kidneys filter creatinine from blood into the urine – Amount of blood that is cleared of creatinine each

minute is called the creatinine clearance. – Creatinine clearance is a good approximation of

the glomerular filtration rate or GFR

Can we estimate GFR from Creatinine?

• YES! Glomerular Filtration Rate can be estimated from serum creatinine measurements.

• Calculated using the Modification of Diet in Renal Disease Equation MDRD, referred to as eGFR.

• GFR (mL/min/1.73 m2) = 175 × (Scr)-1.154 × (Age)-0.203 × (0.742 if female) × (1.212 if African American).

• Takes into account, gender, age, race. • Most thoroughly validated equation

– Caucasians, African Americans ages 18-70 w/GFR< 60

• More useful than creatinine alone, why?

Same creatinine: Very Different GFR

http://www.kidney.org/professionals/kls/pdf/12-10-4004_KBB_FAQs_AboutGFR-1.pdf

Limitations of eGFR: Still an estimate • Not for non-adults • Patients with extremes in muscle

mass or diet – Taking supplements – Obese, amputees

• Creatinine must be stable – Not in pregnancy – Acute illness, hospitalized patients – Acute Kidney Injury

• Will under estimate kidney function in those with near normal function

• Captures only some non-GFR determinants of creatinine

Estimated GFR ml/min/1.73 m2

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Other Methods for Measuring GFR

• CKD-EPI equation – May be more accurate at higher kidney function GFRs – Not as well validated as MDRD

• 24 hr urine collection for creatinine, simultaneous blood Cr, UV/P1440 – Over estimate at low GFRs, eGFR using MDRD is more accurate – Relies on accurate collections, may need to repeat multiple times – Can be useful when eGFRs suspected to be inaccurate

• Inulin, iothalamte, iohexol Clearances – These may be accurate but they are research tools

Stages of Chronic Kidney Disease (CKD)

Urinalysis

Urinalysis

Proteinuria: Protein in the urine • Protein in the urine/proteinuria may

be the first sign of kidney disease • Can be measured by dip stick or urine

albumin/creatinine ratio. • >30mg/g abnormal • 30-300 mg/g microalbuminuria • >300 mg/g macroalbuminuria • 24 hour urine collection: >3g/24h

considered to be nephrotic range • ADPKD is not usually associated with

nephrotic range proteinuria

Glomerular ultrafiltrate should not contain protein

Basic/Comprehensive Metabolic Panel

Why Bone? • When the Kidney isn’t

working (Stage3-4): – Phosphate: – Active form of Vitamin D:

• This results in lower calcium • Signals to the parathyroid

gland to make more PTH. • This causes bone disease. • Your Doctor may check your

Intact PTH level • Rx: Active form of 1, 25

VitaminD

Ref Ranges: Calcium (8.7-10.2) Phosphorus (2.5-4.5)

Liver Function Tests LFTs

• Purpose to monitor liver disease or function • ALT and AST: Enzymes found in the liver cells used to detect liver damage

ie from hepatitis, drugs • Alkaline phosphatase: produced by bile ducts and rises when this is

blocked. Also made by bone, intestine. • Bilirubin: Break down product of red blood cells, modified in the liver,

secreted in bile and urine. Elevated levels cause jaundice • Albumin is a protein made by the liver, binds to hormones, proteins in the

blood

Fasting Lipid Profile (9-12 hours)

• Two types of Lipids transported in blood, cholesterol and Triglycerides, by particles containing different fats and protein (lipoprotein particles).

• Total cholesterol measures all types of cholesterol in these particles. • HDL or “good cholesterol” : excess cholesterol to the liver for removal. • LDL or “bad cholesterol”: Deposits in blood vessels. • Lipid Profile: part of a cardiac risk assessment-risk of heart disease • Treatment depends on the results and other risk factors. • May include life style changes ie diet and exercise, medications.

Questions???

Helpful References

• National Kidney Disease Education Program: http://nkdep.nih.gov/index.shtml

• Lab Tests On Line: http://labtestsonline.org/understanding/ • National Kidney Foundation: Frequently asked questions about GFR:

http://www.kidney.org/professionals/kdoqi/gfr.cfm • National Kidney and Urologic Diseases Information Clearing House

(NKUDIC): http://kidney.niddk.nih.gov/index.aspx • GFR

Calculator:http://www.kidney.org/professionals/kdoqi/gfr_calculator.cfm

• Kidney Function: http://humanphysiology2011.wikispaces.com/12.+Urology