Lab Medicine (Part 1) Flashcards
1
Q
Blood and plasma
A
- Blood constitutes 6 - 8% total body weight
- Plasma comprises 45 - 60% of blood volume
- 5600 ml of blood in the 70 K male
- Normal pH – 7.35 – 7.45
2
Q
Sources of blood collection
A
- Skin puncture
- Venous puncture
- Arterial puncture
3
Q
Skin puncture
A
- Specimen is mixed arterial and venous blood
- Erroenously called “capillary blood”
- May contain interstitial and intracellular fluid
- Useful for glucose monitoring
- Capillary tube utilized for hemataocrit
4
Q
Blood collection technique of choice in pediatrics
A
- Skin puncture
5
Q
Skin puncture technique site selection
A
- Infants: lateral or medial aspect of heel
- Adults: lateral to digital pulps
6
Q
Skin puncture methods of collection
A
- Warming area will increase blood flow (~42 C)
- Prep with alcohol
- Discard first drop
- Do not “milk” area
7
Q
Venous puncture
A
- Composition dependent upon metabolic activity of perfused organs
8
Q
Venous puncture site selection
A
- Antecubital fossa (median cubital vein, cephalic vein)
- Wrist, hand or ankle
- Femoral vein
9
Q
Venous puncture preparation
A
- Cleanse with alcohol
- Apply tourniquet proximal to selected site
- Release tourniquet when blood begins to flow
10
Q
Venous puncture technique
A
- Flexing the hand may facilitate venous distention
- Anchor vein distal and proximal
- Deliver needle: Bevel up, enter at 15 degree angle, direct along proximal path of vein
11
Q
Arterial puncture
A
- Arterial blood uniform throughout body
12
Q
Arterial puncture site selection in adults
A
- Radial artery most common – Allen test
- Femoral artery
- Brachial artery
- Pediatric patient: scalp artery
13
Q
Modified Allen Test
A
- Compress the radial and ulnar arteries until palm of the hand becomes blanched
- Release pressure from the ulnar artery
- The hand should become flushed
- This verifies the ulnar artery can supply the hand
14
Q
Arterial punture technique
A
- Infiltration of local anesthetic may help
- Collect blood gases in heparin tube
- Prep skin with alcohol
- Deliver distal to where the pulse is felt
- Gently mix specimen
- Apply firm compression for a minimum of 5 min
- Transport on ice for blood gases
15
Q
Interpretation of lab values
A
- Look for trends in laboratory values
- All abnormal labs should be repeated
- Osler’s Rule
16
Q
Osler’s rule
A
- Applied to patients <60 years of age
- Seek to attribute all abnormal values to a single pathology
17
Q
Serum collection tubule with coagulants
A
- Red top or SST (tiger top
18
Q
Plasma collection tubule with anti-coagulants
A
- Citrate - blue top
- EDTA - lavender top
- Heparin - green top
- Fluoride - gray top
19
Q
Collection tube uses
A
- Citrate (blue): used for coagulation studies
- EDTA (lavender): blood collections RBC & Luekocytes
- Heparin (green): blood, pophoryns, cortisol, vitamin assays
- Flouride (gray): glucose, lactate, flouride also inhibits glycolysis
- Serum has coagulation factor and plasma does not
20
Q
Coagulation studies
A
- Collect with a sodium citrate tube - blue top
- Citrate was the original anticoagulant (1914)
- Acts via chelation to calcium blocking coagulation cascade
- Adenine increases red cell viability
- PT, PTT, thrombin clotting time
21
Q
Prothrombin time (PT)
A
- Evaluates the extrinsic clotting pathway
Vitamin K dependent factors –II, VII IX, X, protein C and protein S - synthesized in liver
22
Q
Conditions with prolonged PT
A
- Vitamin K deficiency
- Impaired fat absorption
- Liver disease
- Coumadin therapy
23
Q
Prothrombin time reference values
A
- 11 - 13 seconds
- Standardized by “international normalized ratio
24
Q
International normalized rate (INR) calculation
A
(observed PT/control PT) x ISI
25
Prothrombin time prophylaxis values
- For pulmonary embolism - 2.0 - 3.0
| - For mechanical heart valve - 2.5 - 3.5
26
Partial prothrombin time (PTT)
- Best singular test for coagulation
| - Evaluates the intrinsic and final common pathway
27
Partial prothrombin time (PTT) is used for screening of
- Disorders of fibrin formation
| - Heparin therapy
28
Partial prothrombin time (PTT) reference values
- PTT - 60 - 85 seconds
| - aPTT - 30 - 40 seconds
29
Thrombin clotting time (TCT)
- Assesses the terminal steps of pathway
- Evaluates fibrin-fibrinogen interaction by introducing thrombin
- Thrombin induced clotting is very rapid
30
Thrombin clotting time (TCT) elevated when
- Fibrinogen levels are below 100 mg/dl
- Heparin interferes with thrombin action
- Fibrin degradation products are present
31
Thrombin clotting time (TCT) normal reference value
- 10-15 seconds
32
Antifactor Xa assay
- Monitors low-molecular weight heparins and danaparoid
- Rarely warranted
- Renal disease may result in higher than desirable levels
- May be ordered factor deficiencies or in patients with lupus anticoagulants
33
Thrombin clotting time (TCT) reference values
- Not on anticoagulants = 0 units/mL
- Heparin = 0.3 - 0.7 units/mL
- LMWH 30 mg twice daily = 0.4 - 1.1 units/mL
- LMWH 40 mg once daily = 1 - 2 units/mL
- Danaparoid (Orgaran) = 0.5 – 0.8 units/mL
34
Bleeding time
- Good for screening platelet disorders
- Ivy method = forearm with cuff @ 40mm/Hg - < 5 minutes
- Duke method = ear lobe - < 3 minuts
35
Lee-White clotting time
- Oldest but least accurate test
- Time required for clot to form in test tube
- 4 - 8 minutes is normal
36
D-Dimer assay
- Protein released during fibrin clot breakdown
- It is an area of cross-linked fibrin degradation product
- Detected with an ELISA assay
37
D-Dimer assay will elevate with
- Deep venous thombosis
- Pulmonary embolism
- DIC
38
Complete blood count
- Includes data on red and white cells
- Excellent for cell morphology
lavender top tube - EDTA
- EDTA prevents platelet aggregation
39
Red blood cell count
- Expressed as cells per unit volume
- Biconcave disc 6 - 8 µm in diameter (deeper staining periphery, pale central portion should be 1/3 size of cell)
- Life span is ~ 120 days
40
Red blood cell count reference values
- Males 4.6 - 6.2 x 10^6
| - Females 4.2 - 5.4 x 10^6
41
Reticulocytes
- Immature red blood cell
- Circulates for approximately 24 hours
- May be referred to polychromatophilia
- Will increase with anemia when bone marrow is competent
42
Reticulocytes reference values
- ~ 1% (range 0.5 to 1.8%)
43
Hemoglobin
- Main component of red blood cells
- Vehicle for oxygen and carbon dioxide transport
- Concentration obtained by assessing the specific gravity of whole blood
- Depth of staining may be a guide
44
Hemoglobin reference values
- Males - 13.5 - 18 g/dL
| - Females - 12 - 16 g/dL
45
Hematocrit
- Measure of packed red cell volume
| - Expressed as a percentage or decimal fraction
46
Hematocrit reference values
- Males - 40 - 54%
| - Females - 38 - 47%
47
Red blood cell indices
- Calculations based on RBC total, Hb and Hct
- Help determine the size, contend and HB concentration of the RBC
- Useful in characterization of anemia
48
Mean cell volume
- MCV reflects the “volume” of the average cell
| - Calculated from the hematocrit and red cell count
49
Mean cell volume calculation
- (Hct x 1000) / RBC
50
Mean cell volume reference values
- Males - 80 - 98 fl
| - Females - 81 -99 fl
51
Mean cell hemoglobin
- Hemoglobin content or “weight” of average red blood cell
| - Calculated from Hb concentrtion and red cell count
52
Mean cell hemoglobin calculation
- Hb / RBC
53
Mean cell hemoglobin reference values
- Males - 26 - 32 pg
| - Females - 26 - 32 pg
54
Mean cell hemoglobin concentration
- Ratio of the average amount of hemoglobin divided by the average hematocrit
- Represents the average amount of hemoglobin in a set amount of packed cells
55
Mean cell hemoglobin concentration calculation
- Hb/Hct
56
Mean cell hemoglobin concentration reference values
- 32 - 36%
57
Red cell distribution width
- An estimate of anisocytosis
| - First indicator to change in iron deficient anemia secondary to chronic blood loss or dialysis
58
Red cell distribution reference values
- 11.6 - 14.6%
| - Average - 13.1%
59
Erythrocyte morphology color
- A reflection of hemoglobin concentration
- Normochromic
- Hypochromic
- Hyperchromic
- Anisochromia
- Polychromatophilia
60
Normochromic erythrocyte
- Center of biconcave disc is ~1/3 diameter of RBC
61
Hypochromic erythrocyte
- Center of biconcave disc is enlarged and paler
| - Seen in MCH & MCHC
62
Hyperchromic erythrocyte
- Center of biconcave disc is smaller and stain more deeply
| - Megaloblastic anemia
63
Anisochromia
- Reflective of a dimorphic anemia
64
Polychromatophilia
- Reflects the presence of residual RNA within the RBC
- Cells are larger, may lack central pallor
- Represents a reticulocyte or immature RBC
- May be referred to as shift cells
65
Erythrocyte morphology size
- Microcytes
- Macrocytes
- Anisocytosis
66
Microcytes
- Abnormally small
67
Macrocytes
- Abnormally large
68
Anisocytosis
- Variation in size
| - A feature of most anemias
69
Erythrocyte morphology shape
- Poikilocytosis
- Elliptocytes
- Spherocytes
- Target cells
- Shistocytes
- Acanthocytes
70
Poikilocytosis
- Variation in shape
| - Tear drop, helment shaped, oval, pear shaped
71
Elliptocytes
- Iron deficiency anemia myelofibrosis
- Megablastic anemia
- Sickle cell anemia
72
Spherocytes
- Hereditary
- Hemolytic disease
- Splenic condition - hallmark
73
Target cells
- Liver disease
| - Any hypochromia
74
Shistocytes
- Megaloblastic anemia
| - Microangiopathic hemolytic anemia
75
Acanthocytes
- Crenated cells
| - Echinocytes
76
Normocytic anemias secondary to
- Increased blood loss
- Decreased red cell production
- Anemia of chronic disease
77
Normocytic anemias are identified by
- Reticulocyte count
| - Elevated with increased blood loss
78
Acute blood loss
- Trauma
| - “Third” spacing: retroperitoneal pooling
79
Hemolytic disorders
- Hereditary spherocytosis or elliptocytosis
- Sickle cell anemia
- G6PD deficiencies
80
G6PD deficiencies
- Moth ball cells
- Burr cells
- Vulnerable to oxidation
81
Decreased red cell production
- Reticulocyte count is not elevated
| - Primary marrow disease
82
Decreased red cell production other causes
- Human parvo virus B19 - “fifth” disease
- Decreased erythropoietin production
- Hypothyroidism
- Liver disease
83
Anemia of chronic disease
- Associated with chronic inflammatory process (defective red cell production, faulty incorporation of iron)
- Usually normocytic, normochromic (may border on hypochromic, Hb: 9 – 11 g/dl, MCHC ~32)
84
Macrocytic anemia
- From disorders of DNA synthesis in erythrocyte precursors
| - Folate deficiency
85
Folate deficiency
- Absorbed in upper intestine
- Stores last only a few months
- Result of drug therapy (Methotrexate, Phenytoin, Bactrim)
86
Macrocytic anemia(megaloblastic)
- B12 deficiency
| - Pernicious anemia
87
Pernicious anemia
- B12 absorbed in the ileum
- Binds with intrinsic factor
- Neurological disease
88
Pernicious anemia is due to
- Due to gastric mucosal atrophy
| - Autoimmune reaction to gastric parietal cells or intrinsic factor
89
Pernicious anemia (megaloblastic) symptoms
- Neurologic
- Psychologic
- Cardiac
90
Pernicious anemia diagnostics
- Schilling test
- Antibody assay for:
- Abs against parietal cells
- Abs against intrinsic factor
91
Microcytic anemia
- Hb < 7.5 g/dl
| - Decrease in availability or synthesis of Iron, Porphyrin, Globin
92
Microcytic anemia common causes
- Iron-deficiency
- Thalassemia
- Sideroblasts
93
Iron deficient anemia physical findings
- Pallor
- Tachycardia
- Wide pulse pressure
- Vertigo and headache
94
Iron deficient anemia laboratory findings
- Low serum iron and ferritin
| - Elevated TIBC
95
Properties of iron
- 80% of iron is recycled
- Erythropoiesis will not increase if transferrin saturation is maintained between 20-60%
- Iron absorption occurs in the proximal small intestine
96
Daily iron needs
- 1 mg/day – male
| - 1.4 mg/day females
97
Transferrin has
- Two iron binding sites
| - Clearance of Fe+2 is 60-90 min
98
Erythrocyte sedimentation rate
- Rate at which RBC’s precipitate to bottom of vertical tube
99
Erythrocyte sedimentation rate is influenced by
- Rouleaux formation
- Red blood cell factors
- Plasma factors – presence of globulins
100
Erythrocyte sedimentation rate reference values
- Males: 8 mm/hr
- Females: 15 mm/hr
- Increases with age
101
Erythrocyte sedimentation rate red cell factors
- Anemia (Hct ~30-40%)
- Red cell surface area
- Rolleaux formation
102
Erythrocyte sedimentation rate three main uses
- Detecting inflammatory processes
- Monitoring disease course
- Screen for occult neoplastic processes
103
White blood cells
- Granulocytes (neutrophils, eosinophils, basophils)
- Lymphocytes (T cells, B cells)
- Monocytes
104
Absolute cell count calculation
- Total # of WBC’s x % cell type
105
ANC (neutrophils) count
- 1800-7000
| - No elective procedures below 1000
106
Absolute cell count (ACC) values
- Eosinophils = 100-300
- Basophils = 40-100
- Lymphocytes = 1700-3500
- Monocytes = 200-600
107
Neutrophil reference values
- 12 – 15μ diameter
- PMN’s: 56%
- Band cells: 3%
108
Neutrophil role
- First line against bacterial invaders
- Interact with lymphocytes
- Activation of complement
- Phagocytosis
109
Left shift (neutrophils)
- Increase in band cells
- Overall PMN’s > 75%
- Infection is winning because you are using your immature PMNs and have pumped out more PMNs
110
Neutrophilia
- Shift neutrophilia
- Actual influx of band cells from marrow
- Increase in total number of PMNs
111
Causes of neutrophilia
- Infection
- Tissue inflammation
- Surgery – 12-36 hours s/p
- Tissue trauma/injury
112
Neutrophilia from infection
- Elevation of band cells
- Decrease in eosinophils
- Elevation of monocytes
113
Neutrophilia from drugs and chemicals
- Cortisone
| - Heavy metals
114
Neutrophilia from tissue trauma
- Surgery
| - Crush injuries
115
Neutropenia
- Increased risk of bacterial infection
- Congenital
- Chronic infection
- Nutritional
- Acquired
116
Nutritional neutropenia
- B12 and folate
| - Copper
117
Acquired neutropenia
- Drugs
| - heavy metals
118
Eosinophils reference values
- ~ 13μ in diameter
| - 3% of leukocytes
119
Eosinophils role
- Modulate the inflammatory response
- Inactivate mast cells
- Decrease PMN migration
- Poor phagocytosis
- Not bacteriocidal
120
Eosinophilia (CHINA)
- Absolute count > 450/μl (% eos x WBC count)
- Collagen vascular diseases
- Helminthic disease (can directly injure larvae)
- Idiopathic hypereosinophic syndrome
- Neoplasm (lymphomas, gastric and lung carcinomas)
- Allergic
121
Basophils reference values
- 10 – 12μ diameter
| - 1% leukocytes
122
Basophil role
- Possess IgE receptors
| - Tissue mast cells
123
Basophil granules possess
- Histamine
| - Slow reaction substance of anaphylaxis
124
Basophilia
- Absolute value: > 50/μl
- Myeloproliferative disorders
- Chronic hypersensitivity states
