Intro To Lab Med Flashcards
What are the three main exams done on urinalysis?
Physical exam, chemical exam and microscopic exam
What does red urine indicate?
Hematuria - kidney stones, UTI or bladder cancer
What does dark yellow urine indicate?
Dehydration or certain foods (carrots)
What does brown urine indicate?
Glomerulonephritis, myoglobin or bile pigments
What does orange urine indicate?
Medication usage including pyridium
What is the normal range for specific gravity of urine?
1.001 - 1.035
What does an high urine specific gravity indicate?
volume depletion
What does a low urine specific gravity indicate?
excessive fluid intake, diuretic usage, diabetes insipidus
What is the normal range for urine pH?
4.6 - 8.0
What does a high urine pH indicate?
vomiting, UTI, kidney disease
What does a low urine pH indicate?
aspirin overdose, starvation, alcohol usage, high protein diet
What is the normal range for urine protein?
not present
What does protein in the urine indicate?
associated with glomerulonephritis, preeclampsia, diabetes
What is the normal range of urine glucose?
not present
What does glucose in the urine indicate?
blood serum levels about 150-300 will cause glucose to spill into the urine. Indicates diabetes, burns, pancreatitis, corticosteroid usage, Cushing’s syndrome
What is the normal range of ketones in the urine?
not present
What does ketones in the urine indicate?
associated with starvation, alcoholism and diabetic ketoacidosis
What is the normal range for Leukocyte Esterase in the urine?
not present
What does leukocyte esterase in the urine indicate?
It shows that there were enzymes released by WBC indicating UTI. It is not specific to UTI though.
What is the normal range for bilirubin in the urine?
not present
What does bilirubin in the urine indicate?
Bilirubin is a byproduct of Hemolysis. Associated with biliary obstruction and liver injury.
What is the normal range of blood in the urine?
not present
What does blood in the urine indicate?
Associated with kidney stones, urinary trauma, UTI, strenuous exercise, and bladder cancer.
What is the normal range of urobilinogen in the urine?
not present
What does urobilinogen in the urine indicate?
Bilirubin may interact with bacteria in the gut to produce urobilinogen which is associated with hemolysis and hepatocellular disease.
What is the normal range of nitrites in the urine?
not present
What does nitrites in the urine indicate?
Some bacteria convert nitrates into nitrites. Nitrites in the urine suggests bacterial infection which is specific but not sensitive. Negative result does not rule out infection.
What is the normal range of WBC in the urine in microscopic exam?
0 - 5 per high power field
What is the normal range of RBC in the urine in microscopic exam?
0 - 3 per high power field
What does the Bence Jones protein found in the microscopic exam of urine indicate?
Multiple myeloma
What do crystals found in the microscopic exam of urine indicate?
Associated with kidney stones
What do casts in the microscopic exam of urine indicate?
Casts are formed in the distal convoluted tubules of the kidney. They are abnormal proteins formed during infection or inflammation. Red blood casts are associated with glomerulonephritis. White blood casts are associated with pyelonephritis.
What is BUN?
Blood, Urea & Nitrogen
What is the normal range for BUN for adults? What units?
5-20 mg/dL
Urea is produced in the liver as a product of …?
Protein catabolism
Urea is filtered from the blood by the _______.
kidneys
BUN greater than 20 mg/dL indicates…?
- Impaired kidney function
- Increased protein catabolism
- Dehydration
BUN less than 5 mg/dL indicates…?
- Liver failure
- Low protein diet (malnutrition)
- Endocrine disorders (that concentrate urine)
What is the normal creatinine range for men?
…for women? …units?
- Men 0.9-1.2 mg/dL
- Women 0.6-1.1 mg/dL
Elevated BUN + elevated creatinine indicates…?
kidney disease
… these are both excreted by the kidneys
Elevated creatinine indicates…?
- Impaired renal function
- May be a ‘normal’ variant in persons with large muscle mass
Low creatinine level indicates…?
- Low muscle mass (expect low values in bedridden patients)
- Liver disease (creatinine is a product of catabolism in the liver)
Which test has the highest sensitivity and specificity for kidney disease, BUN or creatinine.
Creatinine
Elevated levels indicate kidney disease.
Normal uric acid level for men?
… for women? …units?
- Men 3.4-8.0 mg/dL
- Women 2.4-6 mg/dL
Patients suspected of having gout would have an elevated ________ _____.
Uric acid
Breakdown of nucleic acids forms… ?
Uric acid
Hyperuricemia and can lead to…?
Gout
Increased levels of uric acid may be caused by…?
- Excessive breakdown of nucleic acids
- Excessive destruction of cells
- Inability to excrete (urine)
What does CBC stand for?
complete blood count
What is the principal function of circulating blood?
Transportation of …
- RBCs carrying hemoglobin
- White blood cells for defense
- Platelets responding to injury
What are some indications for ordering a CBC?
- Investigate disease of blood or bone marrow
- Investigate response to inflammation or infection
- Assess symptoms of fatigue, pallor, weakness, unexplained bleeding or bruising, dizziness, fever, or weight loss
What are the 9 common components of a CBC?
White blood cell count Red blood cell count Hemoglobin Hematocrit MCH MCHC MCV RDW Platelets
What does MCHC stand for and measure?
Mean corpuscular hemoglobin concentration - the average concentration of HgB in a given volume of blood.
What does the RDW measure?
Red cell distribution width. Degree of anisocytosis (variation in RBC size). Helps with differentiating anemias and identifying sickle cell anemia.
What is the normal male RBC range?
4.75-5.49 10^6 uL
What is the normal female RBC range?
4.15 - 4.87 10^6 uL
What does MCV stand for in the CBC?
Mean cellular volume (or size/volume of the red blood cell)
What is the normal range of the MCV?
78-98 um^3
What disease process can be ascertained by the MCV?
Two types of Anemia
- MCV is increased (macrocytosis) with vitamin B12 or folic acid deficiency
- MCV is decreased (microcytosis) with iron deficiency anemia
What is the normal range of hemoglobin for men?
14.40 – 16.60 gm/deciliter
What is the normal range of hemoglobin for gals?
12.2 – 14.7 gm/deciliter
What is the significance of the hemoglobin value?
Serves as a vehicle for transportation of oxygen and carbon dioxide - if low, inadequate tissue perfusion
What is hematocrit?
- Proportion of blood that is made up of red blood cells or….
- Percentage of red blood cell/total blood volume
What is the normal range of hematocrit for men?
40-54%
What is the normal range of hematocrit for females?
37-47%
What are some causes of elevated hemoglobin? (5)
- Loss of plasma volume (dehydration)
- high altitude state
- smokers (with COPD)
- CHF
- Polycythema vera
What are some causes of low hemoglobin? (5)
- Increased destruction of red blood cells
- Decreased production of RBCs
- Blood loss
- Pregnancy
- Vitamin deficiency
What diseases can destroy RBCs?
sickle cell disease, thalassemia (inherited blood disorder where hemoglobin is malformed causing RBC destruction)
What organ would be involved with decreased production of RBCs?
kidneys due to low erythropoietin release which helps regulate RBC production in the bone marrow.
What is the normal range for WBCs?
4,500-11,000 x cells/mm^3
Why would WBCs be elevated?
Infection, inflammation or stress
Which WBCs are considered granulocytes?
neutrophils, eosinophils, and basophils
Which WBCs are considered agranulocytes?
lymphocytes and monocytes
What factors should be considered when determining a reference range?
Age, gender, pregnancy status, lab/technique, medication, geographic etc.
What is a Gaussian Distribution?
Gaussian Distribution or a bell-shaped curve, is the most common method of determining a reference range. The curve represents the central 95% of normal, healthy individuals for a given test result. This “normal distribution” or reference range, can be used as a comparison to determine if a pt’s values are within normal limits (WNL).
Identify the purpose of a Screening Test.
Identifies asymptomatic people who may have a disease.
Give examples of common Screening Tests.
Pap smear - cervical CA Fasting blood glucose - DM BP screening - HTN PSA - prostate CA Mammography - breast CA
Identify the purpose of a Diagnostic Test.
Determines the presence or absence of a disease when the pt shows signs or sxs.
Compare reliability vs validity.
Reliability: Consistency or reproducibility of a test under a variety of conditions.
Validity: Accuracy or sensitivity of a test.
Discuss the sensitivity of a test.
Measures the validity of the test for disease orientated individuals. True Positive Rate.
Helps minimize false-negatives.
SNOUT : Sensitive test with a Negative result, rules OUT disease.
A 100% sensitive test would catch all people with the disease. Positive tests do not rule people in though because some without the disease would test positive. If it ruled negative you could trust it.
How is sensitivity calculated?
Sensitivity = true pos. / (true pos. + false neg)
Discuss the specificity of a test.
Correctly identifies healthy individuals or people without disease. True Negative Rate.
Minimizes false-positives.
SPIN = Specific test with Positive results rules IN disease.
A 100% specific test would never test positive for a healthy person. Many people with the disease would test negative though. It would miss a lot of people but if it tested positive you would be sure they have the disease.
How is specificity calculated?
Specificity = true neg / (true neg + false pos)
Name 3 thyroid tests.
TSH, Free T4, T3
Which test is most sensitive for thyroid disorders?
TSH
What condition is associated with increased T4 and T3?
Hyperthyroidism
What condition is associated with decreased T4 and T3?
Hypothyroidism
T/F: You should collect a culture specimen prior to starting antibiotics?
True
What is the ‘Gold Standard’ test for diagnosis of streptococcal pharyngitis?
Throat culture
When would you order a urine culture?
suspected UTI or pyelonephritis
What can you use a sputum culture for?
Diagnosis and treatment of pneumonia and TB. It can also monitor TB therapy.
What test is a marker for generalized inflammation?
Sed rate
What are the two pancreatic enzyme tests?
Amylase
Lipase
Increased levels of Amylase and Lipase may be associated with?
(3)
Pancreatitis
Biliary obstruction
Pancreatic carcinoma
Amylase values and what it means when elevated.
Normal value 10-130 U/L
Enzyme found in the pancreas and salivary glands
Amylase peaks earlier and declines more rapidly with pancreas inflammation
Amylase is less specific for pancreatic inflammation
Lipase values and what it means when its elevated.
Normal value <52 U/L
Lipase remains elevated longer
Lipase is more specific for pancreatic inflammation
Electrolytes Function
Determine the overall fluid status
Acid/base status
What are the Electrolytes that we test for?
Sodium (Na+) Potassium (K+) Chloride Magnesium Calcium
Indications for ordering electrolytes
Patients receiving intravenous fluid
Metabolic or endocrine abnormalities
Medications that interfere with electrolytes
Severe vomiting/diarrhea
Sodium (Normal Value, Function, Regulation)
Normal value (136-145 mmol/L)
Major extracellular cation
Involved with maintenance of blood and body fluids and conduction of impulses
Regulated by osmoreceptors in the hypothalamus
Dehydration stimulates thirst
Overhydration reduces vasopressin and increases urine output
Elevated Sodium causes and values
(>145 mmol/L)
Not enough water in the body (dehydration)
Vomiting and diarrhea
Endocrine (SIADH, aldosteronism, or diabetes insipidus)
Decreased Sodium causes and values
(<136 mmol/L)
Too much water in the body (overhydration)
Endocrine (Cushings disease)
Potassium (Normal Value, Function)
Normal value 3.5- 5.0 mEq/L
Major intracellular cation
Involved in conduction of impulses through membrane depolarization
Elevated Potassium causes
(>5.0 mEq/L)
Cell injury
Kidney failure
Endocrine disorders (Addisons)
Decreased Potassium causes
(<3.5 mEq/L)
Malnutrition
Vomiting and diarrhea
Diuretic medications
Coagulation Studies - why order them?
- Unexplained bleeding disorder or excessive bruising
- Consecutive pregnancy loss
- Patients receiving heparin or coumadin therapy
Prothrombin Time (PT) values
- Normal 11.5-13.5 seconds
- Measure of the ‘extrinsic’ pathway of coagulation (factors I, II, V, VII, X)
- PT test may also be called INR
INR values
- INR (international normalized ratio measures the control against WHO standard)
- Used to monitor patients who are on coumadin therapy, therapeutic value of 2-3.
Partial Thromboplastin Time (aPTT) values
- Normal 27-38 seconds
- Measures ‘intrinsic’ coagulation pathway
- Most commonly used to monitor heparin therapy
Reasons for Prolonged Coagulation Studies
- Patients on coumadin or heparin therapy
- Liver injury (cirrhosis)
- Vitamin K deficiency
What are the liver functions
conjugation of bilirubin
synthesis of proteins and clotting factors
involved in storage and disposal of nutrients, drugs and toxins
What are the liver profile tests (6)
Aspartate aminotransferase (AST) Alanine aminotransferase (ALT) Gamma glutamyl transpeptidase (GGT) Alkaline phosphatase Bilirubin Albumin
What does the AST indicate and its values
Normal value is 7-42 IU/liter
May be elevated with liver, muscle, or cardiac injury
What does the ALT indicate and its values
Normal value is 1-45 IU/liter
More sensitive for liver injury
What does the Alkaline Phosphatase indicate and its values
- Normal value 25-160 IU/L
- Elevated with bile duct obstruction
a. Extrahepatic obstruction (cholecystitis)
b. Intrahepatic obstruction (viral hepatitis or cirrhosis) - This enzyme is not specific to the biliary tract and may be increased with new bone cell production
a. Metastatic bone cancer
What does the Gamma glutamyl transpeptidase (GGT) indicate
- Elevated with liver injury, or biliary obstruction
- Used as a marker of alcohol use
a. Levels may remain elevated long after abstinence from alcohol (3-6 weeks), making it useful for monitoring alcohol treatment programs
What does bilirubin indicate
- Breakdown product of hemoglobin
- Unconjugated bilirubin
a. Bilirubin bound by albumin (not water soluble)
b. Elevated with hemolysis - Conjugated
a. Bilirubin cleaved of albumin (water soluble)
b. Elevated with bile duct obstruction
What does albumin indicate
Protein synthesized in the liver
Marker of liver function
Prothrombin time
- Measures the time required for coagulation to occur
- Coagulation proteins are produced in the liver
- Deficient numbers of coagulation proteins will prolong the prothrombin time
- Marker of liver function
What is the normal value range for Chloride?
97 - 107 mEq/L
What are two causes of elevated chloride levels?
- dehydration
- overactive parathyroid glands
What is a cause of decreased chloride levels?
vomiting (by loss of HCl in gastric acid)
What is the normal value range for Magnesium
1.3 - 2.1 mg/dl
What are two causes of elevated magnesium levels?
- kidney disease
- use of antacids (Milk of Magnesia)
What are two causes of decreased magnesium levels?
- inadequate absorption in GI tract
- medications, such as diuretics
What is the normal value range for Calcium?
8.2 - 10.2 mg/dl
Where is 99% of calcium stored?
in bone
What circulating calcium is metabolically active - 1) protein-bound (with albumin) or 2) ionized
ionized
What are common causes of elevated calcium levels?
- hyperparathyroid hormones
- cancer
- excessive vitamin D
What are common causes of decreased calcium levels?
- hypoparathyroid hormones
- deficient protein
- vitamin D deficiency
What is the fasting blood glucose level?
< 110
Elevated glucose in the blood may be a sign of …?
- diabetes
- endocrine disorders
- pancreatitis
- prednisone therapy
What is the normal value for hemoglobin A1C?
< 5%
What does hemoglobin A1C measure?
Glycosylated hemoglobin (this reflects the average blood glucose over the past 2-3 months and is a useful measure for diabetes management)
