Intro. to Laboratory

Question 1

What are the purposes of diagnostic testing?

Answer 1

1. Diagnosis - rule in or rule out
2. Screening - risk factors, occult disease
3. Patient Management - severity, course, prognosis, and Rx

Question 2

Factors to consider when ordering a test.

Answer 2

1. History and physical exam findings
2. Ability to do something with the results
3. Potential advantages, costs, and disadvantages

Question 3

What is a scope exam (gross pathology exam)? What are some examples?

Answer 3

Visualization of internal organ systems

1. bronchoscopy
2. colonoscopy
3. flexible sigmoidoscopy - distal 2 ft of large intestine
4. Esophagogastroduodenoscopy - endoscopic view of stomach and esophagus
5. Cytoscopy - in bladder

Question 4

What type of exam is an x-ray considered in this context?

Answer 4

According to Dr.Bentley, a gross exam.
Uses radiation to detect variations in density of tissue

Examples:
skeletal - fractures
lungs/chest - tumors/lung pathology
abdominal - pathology of kidney, ureters, bladder

Question 5

What is a myelogram?

Answer 5

X-ray with radio-opaque dye to detect changes

- detects stones, tumors, blockages, spatial changes in bones

Question 6

What is a CT scan?

Answer 6

X-ray of body tissues in small ‘slices’

• can be done with or without contrast
• contrast usu I, Ba, gastrografin based
• can detect bleeds and small structures

Question 7

What is an MRI?

Answer 7

Use of magnetic fields to produce cross-sectional images
- good for soft tissue - masses, tears, bleeds, damage to tissues from infection or injury

• Can be done with gadolinium contrast - contraindicated in pregnant or patients with kidney disfunction

Question 8

What is a biopsy?

Answer 8

A type of cellular path testing

• skin, LN, bone, liver, chest
• small piece of tissue removed and examined histologically

Question 9

What is a puncture biopsy?

Answer 9

Removal of fluid for analysis

- lumbar puncture

Question 10

What is a culture and sensitivities (C&S) assay?

Answer 10

Growth of a bacterium from body fluid to identify pathogen and antibiotic that it is sensitive to
- bacterial ‘lawn’ on plate, with antibiotic paper discs, sensitivity determined by diameter of clear agar around a disc

Question 11

What is a fecal occult blood test?

Answer 11

Small card that indicates presence of blood

• sample obtained during digital rectal exam
• can indicate intestinal neoplasms

Question 12

What is an ultrasound?

Answer 12

Use of sound waves to detect movement and fxn of organs
- no radiation exposure

Examples:
- carotid, venous, abdominal, echocardiogram, and fetus

Doppler - use of sound waves to detect abnormal blood flow in aa or veins

Question 13

What is an electrogram?

Answer 13

Test for electrical activity of a tissue

- EKG, nerve conduction studies

Question 14

What is an angiogram?

Answer 14

Use of radio-opaque dye to detect blockages

• diffuses through pertinent structures
• cardio, pulmonary, and lower extremity angiograms

Question 15

Examples of organ-specific function testing.

Answer 15

1. Ventilation perfusion scan
2. Pulmonary function test
3. Endoscopic retrograde cholangiopancreatography
4. Percutaneous transhepatic cholangiography
5. Ba swallow
6. kidney radionucleotide scan
7. DEXA

Question 16

What is a CBC?

Answer 16

Complete Blood Count
- corresponds with anemias, infections, malignancies

Includes:

• leukocytes (WBCs)
• Erythrocytes (RBCs)
• Hemoglobin (HgB)
• Hematocrit (HCT)

Question 17

What changes levels of hemoglobin?

Answer 17

Increase - dehydration, burns, vomiting, polycythemia, extreme physical exercise
Decrease - all anemias, hypothyroidism, B12 and folate deficiencies, chronic disease

Question 18

What changes levels of hematocrit?

Answer 18

(ratio of volume of RBCs to tot vol of blood)

Increase -high altitude, smokers, tumors, polycythemia vera, heart disease

Decrease - anemias, acute of chronic blood loss, hemolysis, dilutional, alcohol, drugs

Question 19

What changes WBC levels in a CBC?

Answer 19

Usu make up 1% of tot blood volume
- alterations due to infections, hemotological malignancies, leukemias, lymphomas, steroid use, anemias, drugs and sepsis

Question 20

What is a CBC with a differential?

Answer 20

Breakdown of leukocytes according to cell type and number

Neutrophils: PMNs usu 60% of leukocytes

Question 21

Explain left shift versus right shift in a CBC w/ diff.

Answer 21

Left shift - immature cells predominate, indicates bact inf, toxemia, hemorrhage

Right shift - mature cells predominate, indicates liver disease, megaloblastic anemia, iron def disease

Question 22

What can lymphocyte levels in a CBC indicate?

Answer 22

Usu 30% of leukocytes

- increases in viral disease, acute and chronic lymphocytic leukemias, immune disorders

Question 23

What can eosinopil levels in a CBC indicate?

Answer 23

NAACP - neoplasm, addison’s disease, allergy, collagen vascular disease, parasites

Question 24

What can basophil levels in a CBC indicate?

Answer 24

increased - lymphoproliferative disorders, particularly chronic myelogenous leukemia

Question 25

What does prothrombin time test for?

Answer 25

Used to assess coag pathway forming blood clots - standardized to INR - very sensitive to vitamin k dep factors and liver disease When using warfarin/blood thinners use INR to assess efficacy/titrate dose - should be 2-3x normal

Question 26

What does a peripheral blood smear test for?

Answer 26

``` Evaluate morphology of blood cells Detects: - malaria - microcytic hypochromic anemia - lymphoblasts - Basophilic stippling (Pb poisoning, thalassemias) ```

Question 27

What is a basic metabolic panel and what does it test for?

Answer 27

Measures levels of noncellular elements of the blood, levels affected by different diseases - Na+ - Cl- - HCO3- (buffer) - K+ (nerve excitation, mm contraction, myocardial potential)

Question 28

What is a blood glucose test?

Answer 28

Indicates variety of metabolic disorders if it falls outside normal fasting range of 7-100 mg/dL

Question 29

What is a hemoglobin A1c test for?

Answer 29

Measures levels of blood sugar over life of a circulating RBC - 6 weeks - 6 week timeline to monitor blood sugar levels, diabetes control - Fe deficiency anemia can elevate A1c levels

Question 30

What is a renal function study?

Answer 30

Measure of BUN and creatine levels - BUN:Cr ratio is used to id source of pathology BUN:Cr >20:1 = prerenal 10-20:1 = normal <10:1 = intrarenal

Question 31

What do bilirubin levels indicate in liver function tests?

Answer 31

- mostly derived from breakdown of heme Total: increased with hepatic damage, biliary obstruction, hemolysis Direct, conjugated: increased with biliary obstruction, Dubin-Johnson syndrome, Rotor Syndrome Indirect, unconjugated: caused by hemolysis, decreased hepatic uptake

Question 32

What do liver function enzymes indicate in a liver function study?

Answer 32

Alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkalophosphatase (alk phos), and gamma glutamyl transferase (GGT) Indicates malignancies, alcohol abuse (chronic), liver disease

Question 33

What does C-reactive protein indicate?

Answer 33

Acute phase, short half life | - indicates inflammation or tissue injury, particularly with MI

Question 34

What does a lipid panel indicate?

Answer 34

Total, with LDL and HDL and LDL as well as tot triglycerides | - important indicators about diet, health, and risk factors for CV disease

Question 35

What do thyroid studies measure?

Answer 35

TSH levels - thyroid stimulating hormone - secreted by pituitary, induces secretion of thyroxine from thyroid gland - important regulator of metabolism - high in hypothyroid patients

Question 36

Explain what urine analysis tests for and how it is performed.

Answer 36

Dipstick test Evaluates: - appearance - cloudy, foamy, etc. - specific gravity - blood - ketones - protein - nitrites - leukocyte esterase