Urine Dipstick Flashcards
Learn everything about the urinalysis dipstick
What causes cloudy, red urine?
Red blood cells present (Hematuria)
What is normal urine pH?
Normal: slightly acidic (6.0) Random (4.4 - 8.0)
What causes the yellow color in urine?
Urochrome
What is the normal specific gravity of urine?
1.002 - 1.035
What is the highest concentration urine can reach?
1.040
What could cause a specific gravity above 1.040
Large amounts of glucose or radiographic dyes from x-ray procedures
What is the principle of protein detection on the dipstick?
The protein error of indicators - pH of strip 3.0 - dye changes color of strip
What protein does the the dipstick test detect?
Albumin
What causes false positives on the protein test?
Highly alkaline urine - highly pigmented urine - quaternary ammonium compounds, detergents, antiseptics, chlorhexadine
What causes false negatives on the protein test?
High salt
What is the clinical significance of the protein test?
Detects proteinuria - best single indicator of renal disease - can be caused by strenuous exercise
What causes false postives on the pH test?
No known causes
What causes false negatives on the pH test?
No known causes
What is the clinical clinical significance of the pH?
Alkaline urine can indicate “old” urine - sometimes seen after eating (this is in response to HCl secretion)
What is the principle of pH detection on the dipstick?
2 indicators, methyl red (red/orange -> yellow) and bromthylmol blue (green -> blue) - 2 indicators provide a wide spectrum of color changes
What is the principle of glucose detection on the dipstick?
Glucose oxidase method (double sequential enzyme) - glucose oxidase catalyzes rxn with glucose + O2 > gluconic acid and H2O2 - H2O2 catalyzes rxn between with chromogen to form oxidized colored compound - direct proportion to glucose concentration
What causes a false positive on the glucose test?
Bleach
What causes a false negative on the glucose test?
Vitamin C (newer strips are more resistant) -
What could Bence Jones proteins indicate?
Multiple myleoma (plasma cell myleoma)
what is the term for glucose in the urine?
Glycosuria
What is the renal threshold for glucose?
160 to 180 mg/dL
What effect does epinephrine have on urine glucose levels?
Inhibits the effect of insulin - seen with stress, cerebral trauma, and myocardial infarction
What hormonal disorders cause glycosuria?
Pancreatitis, pancreatic cancer, acromegaly, Cushing’s syndrome, hperthydoidism, pheochromocytoma
What are the causes of renal glycosuria?
Tubular reabsorption disorder, end-stage renal disease, cystinosis, Fanconi syndrome, temporary lowering of renal threshold in pregnancy
What chromogens are used in the glucose test?
KI (green to brown - Multistix) and tetramethylbenzidine (yellow to green - Chemstrip)
What causes false positives in the glucose test?
H2O2 and oxidizing detergents like bleach
What are the three intermediate products of fat metabolism?
Acetone (2%), Acetoacetic acid (20%), and β-hydroxybutyrate (78%)
What causes ketones to appear in urine?
Body stores of fat are metabolized to supply energy
What are the primary causes of keonuria?
Diabetes mellitus, vomiting (loss of carbohydrates), starvation, malabsorption, dieting
What is diabetic ketoacidosis?
Increased accumulation of ketones in the blood due to diabetes - can lead to electrolyte imbalance, dehydration, and diabetic coma
What are some causes of ketonuria that aren’t related to diabetes?
Inadequate intake/ absorption of carbohydrates, vomiting, weight loss, eating disorders, frequent strenuous exercise
Why should a diabetic monitor their ketonuria?
Keturnia is a sign of insulin deficiency and can be used to help monitor diabetes
What is the primary reagent used in the ketone test?
Sodium nitroprusside (nitroferricyanide)
What does the ketone test detect?
Acetoacetic acid - assumes the presence of acetone and
β-hydroxybutyrate
What is the principle reaction of the ketone test?
Sodium nitroprusside + acetoacetic acid (alkaline) = purple color
What could cause false positive results in the ketone test?
Highly pigmented urine, levodopa in high doses, medications contain sulfhydryl groups, improperly timed readings
What could cause false positive results in the ketone test?
Improperly preserved specimens (bacteria break down acetoacetic acid by bacteria)
What causes clear red urine?
Hemoglobinuria, product of red blood cell destruction
How much blood in the urine is considered clinically significant?
Any amount of blood greater than 5 red blood cells
What test is most accurate for determining the presence of hemoglobin in urine?
Chemical test
What method can be used to differentiate between hematuria and hemoglobinuria?
Microscopic examination
What are some causes of hematuria?
Renal calculi, glomerular disease, tumors, trauma, pyelonephritis, exposure to toxic chemicals, anticoaglulants
What causes clear red urine?
Hemoglobinuria
What are some causes of hemoglobinuria?
Transfusion reactions, hemolytic anemias, severe burns, infections/malaria, strenuous excercise/RBC trauma, brown recluse spider bites
The lysis of red blood cells in dilute, alkiline urine can cause what?
Hemoglobinuria
What is hemosiderin?
Yellow brown granules in urine sediment
What is the cause of clear red/brown urine?
Myoglobinuria
What is the cause of myoglobinuria?
Rhabdomyolysis (muscle destruction)
What are some causes of rhabdomyolysis?
Muscular trauma/crush syndromes, prolonged coma, convulsions, muscle-wasting disease, alcoholism, drug abuse, extensive exertion, statins
What is the mechanism of the blood test reagent?
H2O2 reacts with the heme component of blood which produces O2 > O2 + tetramethylbenzidine (chromogen) = color change
What color changes are indicated on the blood test pad?
Free hemoglobin shows uniform color - intact RBCs show a speckled pattern
What could cause a false positive on the blood test?
Menstrual contamination, strong oxidizing agents, bacterial peroxidases
What could cause a false negative on the blood test?
Vitamin C (>25 mg/dL), high SG/crenated cells, formalin, catopril, high concentrations of nitrite, unmixed specimens
Is conjugated bilirubin water soluble?
Yes
Is unconjugated bilirubin water soluble?
No (conjugated with glucuronic acid)
What is the clinical significance of bilirubin?
Liver damage ( hepatitis and cirrhosis) - hemolytic anemeas
What is the principle of the urobilinogen reaction?
Diazo reaction (Chemstrip), white to pink - dimethlyaminonbinzaldehyde + urobilinogen = peach to pink color (Ehrlich’s reaction - Multistix)
What could cause a false positive in the urobilinogen test?
Urine pigments, phenazopyridine, drugs like indican and iodine
What could cause a false negative in the urobilinogen test?
Old specimens (biliverdin does not react), Vitamin C (>25 mg/dL), nitrite
What is the ictotest confirmatory for?
Bilirubin
What does a +++ bilirubin and normal urobilinogen test indicate?
Bile duct obstruction
What does a + or - bilirubin and ++ urobilinogen test indicate?
Liver damage
What does a negative bilirubin and +++ urobilinogen test indicate?
Hemolytic disease
What is the clinical significance of the nitrite test?
Bacteria (UTI)
What is the reaction principle for the nitrite test?
Nitrite + amine reagent = diazo compound > diazo compound + 3-hydroxy-1,2,3,4 tetrahydrobenz-(h)-quinolin = pink color
What could cause a false positive on the nitrite test?
Old specimens, highly pigmented urine
What could cause a false negative on the nitrite test?
Nonreductase containing bacteria, insufficient contact time between between bacteria and urinary NO3, lack of urinary NO3, large quantities of bacteria converting N02 to N2, presence of antibiotics, high concentrations of vitamin C, high SG
When should you repeat a nitrite test?
When negative results are obtained in the presence of clinical symptoms, even if symptoms are vague
What is the clinical significance of the leukocyte esterase test?
Indicates WBCs in the urine which like corresponds to a bacterial infection
Does the leukocyte esterase detect granulocytes or lymphocytes?
Granulocytes
What is the reaction principle of the leukocyte esterase test?
Leukocyte esterase splits ester to form pyrrole compound > pyrrole compound + diazo reagent = purple color
What could cause a false positive on the leukocyte esterase test?
Strong oxidizing agents, formalin, highly pigmented urine (nitrofurantoin)
What could cause a false negative on the leukocyte esterase test?
High conc. of protein, glucose, oxalic acid, Vitamin C - Crenation from high SG - inaccurate timing (must have 2 minutes) - presence of antibiotics (gentamicin, cephalosporins, tetracyclines)
What is the reaction principle of specific gravity?
pKa change of polyelectrolyte
What reagent is used for the specific gravity test?
Bromthymol blue
Why is the specific gravity test more accurate than the refractometer?
High MW compound, glucose, plasma expanders, and radiographic dye do not influence the test
What could cause a decreased reading of the specific gravity?
A pH of 6.5 or higher - add 0.005 to the reading - automated readers automatically account for this
What could cause a false positive on the specific gravity test?
Protein
What could cause a false negative on the specific gravity test?
Alkaline urine
Characteristic odor of PKU urine
Mousy
Characteristic odor of cystinosis
Sulfur
Characteristic odor of isovaleric acidemia
Sweaty feat
What is the functional unit of the kidney?
The nephron
What are the causes of focal segmental glomerulosclerosis?
Abuse of heroin and analgesics; AIDS
How to prepare specimen for microscopic examination?
Mix urine, decant 12 mL into tube. Centrifuge for 5 minutes at 400 RCF
What causes dirty casts?
Hemoglobin degradation products such as methemoglobin; associated with acute tubular necrosis
What are the three ways to determine specific gravity?
Refractometer, reagent strip, osmolality
What is the Acetest confirmatory for?
Ketones
What does the Clinitest test for?
Determines the amount of reducing substances (generally glucose) in urine
What is the purpose of the sulfosalicylic acid precipitation test?
It reacts equally with all types of proteins not just albumin
Pathogenic crystals are found in what urine pH?
Acidic, sometimes neurtral
What crystals are associated with liver disease?
Leucine, tyrosine, and bilirubin
What crystals are associated with cystinuria?
Cystine
What crystals are associated with nephrotic syndrome?
Cholesterol
What normal crystals are found in acidic urine?
Uric acid, amorphous urates
What crystals are seen in acid, neutral, and sometimes acidic urine?
Calcium oxalate
What crystals are seen in alkaline urine?
Amorphous phosphates, calcium phosphate, triple phosphate, ammonium biurate, calcium carbonate
What crystals precipitate after refrigeration?
Amorphous phosphates
What type of microscopy is typically used in urine microscopy assessment?
Bright-field microscopy
What is the renal threshold of glucose?
160-180 mg/dL
Diabetes insipidus vs diabetes mellitis
Both are pale urine; insipidus has low SG; melllitis has high SG
What is pyelonephritis?
Infection of the renal tubules
What is glmerulonephritis?
An inflammation of the glomerulus that results in impaired glomerular filtration
What urine findings are present in acute pyelonephritis?
Numerous leukocytes and bacteria with mild proteinuria and hematuria; WBC casts and bacterial casts may also be present
What urine findings are present in acute glomerulonephritis?
Macroscopic hematuria, proteinuria, RBC casts, and granular casts
What age group is primarily affected by Henoch-Schonlein purpura?
Children
What urine findings are present in Henoch-Schonlein purpura?
Macroscopic hematuria, proteinuria, RBC casts
What is the cause of Henoch-Schonlein purpura?
Occurs after upper respiratory infections
What is Lesch-Nyhan disease?
A disorder of purine metabolism that results in massive excretion of urinary uric acid crystals resembling orange sand in diapers
What are the urine characteristics of Fanconi syndrome?
Glycosuria with a normal blood glucose and possible mild proteinuria. Urinary pH can be low due to failure to reabsorb bicarbonate
What are the symptoms of acute renal failure?
Decreased glomerular filtration rate, oliguria, edema, and azotemia (steadily rising serum BUN and creatinine levels)
What is azotemia?
Steadily rising serum BUN and creatinine levels
What urine findings are present in acute renal failure?
RTE cells and casts indicate prerenal origin; RBCs indicate glomerular injury; WBC casts with or without bacteria indicate interstitial infection or inflammation or renal origin; postrenal obstruction may show normal or abnormal apperaring urothelial cells
What are the causes of prerenal ARF?
Decreased BP/cardiac output, hemorrhage, burns, surgery, septicemia
What are the causes of renal ARF?
Acute glomerulonephritis, acute tubular necrosis, acute pyelonephritis, acute interstitial nephritis
What are the causes of postrenal ARF?
Renal calculi and tumors
Good pasture syndrome and Wegener’s granulomatosis – what do we find in urine sediment?
Blood, protein, and RBC casts
- Nephrotic syndrome – what do we see in urine sediment?
Heavy proteinuria, microscopic hematuria, renal tubular cells, oval fat bodies, fat droplets, fatty and waxy casts
What crystals are seen in nephrotic syndrome?
Cholesterol
What is diabetic nephropathy?
The most common cause of end-stage renal disease; caused by damage to the glomerular membrane as the result of glomerular membrane thickening and increased deposition of cellular and noncellular material within the glomerular matrix resulting in solid substances around the capillary tufts
