Lab Interpretation Flashcards
(44 cards)
Sensitivity
The ability to correctly identify who HAS a disease
Specificity
The ability to correctly identify who does NOT have the disease
Positive Predictive Value
Proportion of positive tests that are truly positive. Also referred to as the “precision rate.” Proportion of positive tests that are truly positive.
Negative Predictive Value
Number of true negatives out of all people who test negative.
Complete Blood Count (CBC)
White Blood Cell (WBC) Red Blood Cell (RBC) Hemoglobin (HgB) Hematocrit (HcT) Mean Corpuscular Volume (MCV) Mean Corpuscular Hemoglobin (MCH) Mean Corpuscular HgB Concentration (MCHC) Red Cell Distribution Width (RDW) Platelets (PLT)
CBC Fishbone
WBC // Hemoglobin / Hematocrit // PLT
White Blood Cell Count…
WBC is sensitive… but non-specific!
Elevated due to infection, acute stress, air pollution, medications, leukemias
Depressed: yellow fever, amebiasis
“You know something is wrong somewhere, but it doesn’t give you the full clinical picture”
White Blood Cell Differential
Takes more time, and may be more expensive…
Ordered when CBC count is elevated
Differential Count: Basophils (0.5 - 1%) Eosinophils (1-4%) Neutrophils (40-60%) Monocytes (2-8%) Lymphocytes (20-40%)
Differential % always equal 100%.
Absolute Differential
WBC count by % of cell type
Basophils
Least common of all the WBCs
Increase in response to same conditions that cause increased eosinophils
Release histamine, bradykinin & serotonin activated by injury or infection
Medications - increase: antithyroid therapy / decrease glucocorticoids, antonioplastics
Eosinophils
Defend against parasitic infection
Part of the allergic response
Often found in sputum of patients with asthma
Medications that increase eosinophils: Digoxin, Heparin, PCN, Propanolol
Medications that decrease it: corticosteroids
Neutrophils
Most numerous WBC but most short-lived
Increased production during acute stress
Types:
Banded/”Bands” –> Immature (5%)
Segmented/”Segs” –> Mature (95%)
Left Shift: Increased # of bands (immature). When someone is acutely ill, body will respond by producing more baby neutrophils
Causes of Neutrophilia
Bacterial infection
Medications: Lithium, Steroids, Heparin
Cigarette Smoking
Obesity
Causes of Neutrophilia
Bacterial infection
Medications: Lithium, Steroids, Heparin
Cigarette Smoking (increased # of ‘segs’)
Obesity (increased # of ‘segs’)
Monocytes
Produced by Marrow –> Circulates 5-8 days –> Enter tissue and becomes histiocyte
Not common in circulating blood
Lymphocytes
2nd most numerous WBC
Main function: immune response
T & B cells
Medications that decrease lymphocytes: glucocorticoids, immunosuppressants
Lymphocytes (continued)
Elevated: mononucleosis, TB, pertussis, influenza
Depressed: AIDS, Aplastic Anemia, MS, GBS. Medications that cause depression: steroids
Leukocytosis
Usually due to neutrophils of lymphocytes
of neutrophils increases the severity of infection
Total WBC count reflects quality of immune system
% of Neutrophils…
Indicates severity of infection
Total WBC…
Reflects quality of immune system
Leukocytes Scenario #1
25 yo with pneumonia
Total WBC = 18,000
Neutrophils = 60% (10,800)
Moderate infection with good immune response!
Leukocytes Scenario #1
25 yo with pneumonia
Total WBC = 18,000
Neutrophils = 60% (10,800)
Moderate infection with good immune response!
Leukocytes Scenario #2
85 yo with pneumonia
Total WBC = 11,500
Neutrophils = 80% (9,200)
Bands = 10%
Severe infection with poor immune response
Leukocytes Scenario #2
85 yo with pneumonia
Total WBC = 11,500
Neutrophils = 80% (9,200) // Normal is 40-60
Bands = 10%
Severe infection with poor immune response
Red Blood Cells (Erythrocytes)
Produced in bone marrow. Stimulated by erythropoietin.
Lifespan: 120 days
Anemia: at least a 10% decrease in RBC
