Diagnostic Testing Flashcards
Specificity
Ability of a test to correctly identify those who do NOT have the disease
Sensitivity
Ability of a test to diagnose those who have the disease
Incidence
Number of new cases during a specific period, in a specific population
Prevalence
Number of existing cases at a specific time, in a specific population
Predictive value
Ability of a screening test to correctly identify the disease state.
CBC
Complete Blood Count
WBC: Definition and Normal Range
White Blood Cells
5,000-10,000
Low WBC count
Leukopenia
High WBC count
Leukocytes is
Bashophil: Normal range and Response
(0.1-2%)
Inflammatory and allergy response
Eosinophil- Normal Range and Response
(1-5%)
Allergic response (asthma, parasites)
Monocytes- Normal Range and Response
(4-13%)
Fighting infection and foreign bodies
Neutrophils- Normal Range and Response
(40-70%)
Bacterial Infections
Lymphocytes- Normal Range and Response
(20-40%)
Viral Infections
Red Blood Cells- Normal Range
Erythrocytes or red blood corpuscle
4.5-5.5 million
Polycythemia
Increase in red blood cells
Hemoglobin- normal range for men/women
The protein on red blood cells that carries oxygen
Men- 14-18g/dL
Women- 12-16g/dL
Hematocrit- Normal range for men/women
Amount of red blood cells compared to the total blood volume
Men- 42-52%
Women- 37-47%
MCV- Normal Range
Mean corpuscular volume- size of the red blood cells
80-100 fl
MCH- Normal range
Mean corpuscular hemoglobin- amount of hemoglobin in red blood cells
27-33
MCHC- normal range
Mean corpuscular hemoglobin concentration- concentration of hemoglobin in red blood cells
33-36g/dL
RDW- normal range
Red cell distribution width- variation of RBC size
11-15%
Platelets- Normal Range
Used in clotting
150,000-400,000
Thrombocytopenia
Low platelet count
R/O bleeding
Thrombocytosis
High platelet count
R/o clotting
MPV- normal range
Mean platelet volume- average size of platelets
7-10 fl
What does a “left shift” mean?
Increased number of immature forms blood cells (bands = baby white cells)
There are more band cells (% bands) in a CBC with differential.
If the body is producing and mobilizing a large number of new white cells, then the body is attempting to fight off a very active infection. Normally, we only have 2-6% of our white cells as bands. If this increases, then the infection is causing the body to release bands (baby white cells) into the body before they are ready to join the fight.
Urinalysis
Panel of tests with evaluates the urinate evaluate for disease
What are the three things a urinalysis analyses?
Gross inspection- color, turbidity
Dipstick- specific gravity, pH, glucose, heme, protein, leukocytes, nitrites (ketones, bilirubin, urobilinogen)
Microscopy- quantify WBCs and RBCs and inspect for bacteria, crystals and casts
Urinalysis Color
Hydration status
Influenced by medical conditions, medications, and ingested food
Turbidity of Urine
Clear or cloudy
Specific Gravity of Urine
Density of urine/Density of water
1.001-1.035
In healthy people- slightly below 1.010
1.001- more dilute. Diabetes insipidus, hydrated, ATN
1.035- dehydration, SIADH,CHF, cirrhosis, glycosuria, proteinuria, recent IV contrast
~1.010 (fixed)- advanced kidney failure, kidneys are regulating
PH of urine
4.5-8.0
Low pH- acidemia
High pH- UTI, alkalemia, Distal RTA
Urine pH is highly dependent on diet, cannot be used to infer anything about the acid-base status of a patient in the absence of an ABG and metabolic panel.
Glucose
Glycosuria
Hyperglycemia
Proximal tubule dysfunction
Glycosuria can lead to osmotic diuresis and dehydration
Heme
Hematuria (many causes)
Rhabdomylosis
Protein
Highly dependent of urine concentration
1:4 scale
Glomerular disease
Overflow proteinuria
Post-renal proteinuria (UTI)
Leukocyte estrange and nitrites
Aid in diagnosis of UTI’s
L.E.- enzyme related by WBCs used as a qualitative measure of WBCs in the urinary tract. (Inflammation marker)
Nitrites- detect the presence of enterobacteriacae which convert nitrates to nitrites. (Bacteria)
Ketones
Poorly controlled DM with additional trigger (infection, MI), alcoholic, starvation
Ketogenic diets
Poor sensitivity
Urine Microscopy
Urine viewed under the microscope
Microscopy- RBCs
or more RBCs/HPF abnormal.
UTI, renal stones, GU malignancies, recent instrumentation, coagulopathy, glomerulonephritis, sickle cell anemia, renal tuberculosis, vigorous exercise, contamination with menstrual blood.
Needs urology work up if continues to be high
Microscopy-WBCs
> 5 generally abnormal
Bacteria
Consistent with UTI
If L.E. And nitrates are negative consider poor collection technique
Using UA to diagnose a UTI
Presence of nitrites is the most specific finding, highest positive predictive value.
Consider the presence of symptoms and a positive urine culture
Crystals
Highly organized, microscopic solids usually composed of a small number of ions and molecules.
Dependent upon urine pH and concentration of ions and molecules.
Small amounts of most types are not necessarily pathologic
Six types of crystals
Uric acid (tumor lysis syndrome- first round of chemo)
Calcium phosphate- (alkaline urine- Not suggestive of systemic disease)
Magnesium ammonium phosphate- (alkaline urine- UTIs by urease-producing organisms)
Calcium opal ate dihydrate-(independent of pH- not suggestive of systemic disease)
Calcium oxalate monohydrate-(independent of pH- ethylene glycol ingestion)
Cystine- (acid urine- cystinuria)
Casts
Long, cylindrical structures formed in the renal tubules due to precipitation of Tamm-Horsefall much protein.
Promoted by acidic and/or concentrated urine
Described based on the elements embedded within the mucoprotein matrix
Insight into etiologies of AKI
Types of casts
Acellular
-Hyaline- without other constituents- non-specific, dehydration
-Muddy brown- ATN
-Waxy- Kidney disease
-Fatty- nephrotic syndrome
-Pigment- one of several colored compounds (heme, bilirubin…)
-Granular- degeneration of a cellular gast
Cellular
-RBC- glomerulonephritis
-WBC- interstitial inflammation
