urinalysis

Question 1

What is a clean catch urine ssample

Answer 1

collected midstream

Question 2

Methods of urine collection

Answer 2

random collection is taken at any time of day with no precautions (urine may be dilute, isotonic or hypertonic), eraly morning sample before ingestion of fluids (hypertonic), catheterization of bladder or suprapubic needle aspiration of bladder

Question 3

What causes foul, sweet, fruity or maple-syrup like smelling urine

Answer 3

Foul, offensive: Old specimen, pus or inflammation. Sweet: Glucose. Fruity: Ketones. Maple syrup-like: (Maple Syrup Urine Disease)

Question 4

What causes deep yeelo, yello-green, red, brownish-red and brownish-black colored urine?

Answer 4

Deep Yellow: Concentrated Urine, Riboflavin. Yellow-Green: Bilirubin / Biliverdin. Red: Blood / Hemoglobin. Brownish-red : Acidified Blood (Acute GN). Brownish-black: Homogentisic acid (Melanin)

Question 5

How is glucose detected by urine dipstick?

Answer 5

Glucose oxidase converts glucose + water and O2 to gluconic acid and peroxide. Then, Horseradish peroxidase converts peroxide + KI (also on the strip) to KIO3 and water, then the oxygen liberated binds with dye forming a colored substrate

Question 6

False negative glucose urine dipstick

Answer 6

As ascorbic acid is an oxygen acceptor and most likely to be present in large amounts in the urine of pregnant women, this will cause a false-negative result. Also, this can not detect sugars other than glucose, so not beneficial in newborn screens

Question 7

Another method used to detect sugars

Answer 7

CuSO4 can detect reducing sugars: Galactose (galactosemias), fructose (fructose intolerance), lactose (lactase deficiency), pentoses (essential pentosuria), maltose (non-pathogenic). NOT sucrose b/c it is not reducing

Question 8

How is bilirubin detected by urine dipstick?

Answer 8

Bilirubin combines with a diazo salt in an acidic medium to form azobilirubin which forms a light-dark tan color.

Question 9

False negative and positive bilirubin are caused by…

Answer 9

Indican (indoxyl sulfate) will cause a false-positive result, while ascorbate will cause a false-negative result

Question 10

Limitations of urine bilirubin dipstick

Answer 10

Only measure direct bilirubin (which correlates with urobilinogen and serum bilirubin), not indirect. Interference can occur with prolonged exposure of sample to light.

Question 11

Other methods for measuring bilirubin

Answer 11

Ictotest (more sensitive tablet version of same assay) and serum test for total and direct bilirubin

Question 12

How are ketones detected by urine dipstick?

Answer 12

The ketones (acetoacetate) reacts with nitroprusside to form a purple color Also detects acetone but not beta-hydroxybutyrate

Question 13

What causes ketones in urine

Answer 13

Diabetic ketosis or other form of calorie deprivation

Question 14

Limitations of urine ketone detection

Answer 14

Interference can occur with expired reagents(due to degradation with exposure to moisture in air) and it only measures acetoacetate, not other ketone bodies.

Question 15

Other methods for urine keytone detection

Answer 15

Ketostix (more sensitive tablet version of same assay) and serum glucose measurement to confirm Diabetic ketoacidosis.

Question 16

How is specific gravity measured by urine dipstick?

Answer 16

by measuring the change in pKa of polyelectrolytes in relation to ionic concentration

Question 17

What is the normal range for urine specific gravity

Answer 17

1.003-1.035

Question 18

Uses and limitations of urine specific gravity

Answer 18

Useful for diabetes insipidus. Limitations: alkaline urine interferes with test and does not measure non-ionized solutes such as glucose.

Question 19

Other methods for urine specific gravity detection

Answer 19

refractometry, hydrometer, osmolality measurement

Question 20

What will show up as a positive in the urine blood dipstick

Answer 20

RBCs, free hemoglobin or free myoglobin. While hemoglobin and RBCs are normally too large to pass through glomerulus, myoglobin passes freely through glomerulus.

Question 21

How is blood detected by urine dipstick

Answer 21

pseudoperoxidase reaction, which is more sensitive to hemoglobin and myoglobin than intact RBCs.

Question 22

Describe urine in hematuria vs hemoglobinuria

Answer 22

In cases of hematuria, the urine is red and cloudy, but will clear if centrifuged.Hemoglobinuria will have reddish brown urine that does not become clear after centrifugation

Question 23

Normal range of urine pH, and causes of high/low pH

Answer 23

Normal is 4.5-8.0. Acidic urine 8.0 occurs in renal tubular acidosis.

Question 24

Interference of urine pH test

Answer 24

bacterial overgrowth (alkaline or acidic), or “run over effect” effect of protein pad on pH indicator pad where buffers from protein area of strip spill over to pH area and make pH appear more acidic than it really is.

Question 25

Other methods for urine pH

Answer 25

Acidity titer and blood gases

Question 26

define proteinuria

Answer 26

>150mg/ day protein in urine.

Question 27

How are proteins measured by urine dipstick and its limitations

Answer 27

Bromophenol blue is used as an indicator dye. It is most sensitive to albumin and interference occurs with highly alkaline urine.

Question 28

Other tests for urine protein detection

Answer 28

sulfosalicylic acid can detect albumins, globulins, and Bence Jones protein. Urine protein electrophoresis

Question 29

Which proteins can be found in normal urine

Answer 29

albumin, Tamm-Horsfall, immunoglobulins, secretory IgA all at small amounts

Question 30

What is urobilinogen

Answer 30

Urobilinogen is formed by intestinal bacteria from the breakdown of conjugated bilirubin, and it is usually excreted in feces. However a small amount may be reabsorbed and excreted in urine

Question 31

How is urobilinogen detected on urine dipstick

Answer 31

based on a modified Ehrlich reaction, in which p-dimethyl amino benzaldehyde in conjunction with a color enhancer reacts with urobilinogen in a strongly acid medium to produce a pink-red color. A positive test response indicates normal enterohepatic circulation of biliary pigments. High concentrations of biliary pigments may occur in hemolytic crisis, or cases of hepatic or intestinal dysfunction. Low indicaties bile obstruction

Question 32

Causes of a false positive and false negative urobilinogen urine test

Answer 32

A false positive test result may occur if the temperature of the reagent strip is elevated. A false negative test result may occur if there is formalin residue in the collection container, or if the sample is old, because urobilinogen is very unstable when exposed to light and air.

Question 33

What causes nitrites in the urine

Answer 33

A positive nitrite test indicates that bacteria may be present in significant numbers in urine. Gram negative rods such as E. coli are more likely to give a positive test.

Question 34

What causes positive leukocyte esteraste in urine

Answer 34

A positive leukocyte esterase test results from the presence of white blood cells either as whole cells or as lysed cells. If negative, there is no need t loo for further signs of infection

Question 35

Causes of false positive and false negative leukocyte esterase in urine

Answer 35

False positive test results also may occur in the event of vaginal contamination. False negative test results may develop if the patient has been treated with high doses of antibiotics. Glucosuria or increased urine specific gravity may cause false negative test results

Question 36

Preservation of cells/casts for microscopic analysis

Answer 36

Cells and casts begin to disintegrate in 1 - 3 hrs. at room temp. Refrigeration for up to 48 hours (little loss of cells).

Question 37

For a high power field, what is the definition of abnormal: erythrocytes, leukocytes, renal tubular cells , bacteria, neutrophils

Answer 37

Per high power field (400x): > 3 erythrocytes, >5 leukocytes, >2 renal tubular cells, >10 bacteria, >1 neutrophil per 3 HPF

Question 38

For low power field, what is the definition of abnormal: hyaline/granular casts, squamous cells, RBC/WBC casts

Answer 38

per low power field (200x): >3 hyaline casts or >1 granular cast, >10 squamous cells (contamination), any number of RBC/WBC casts

Question 39

Causes of hematuria and dysmorphic RBCs

Answer 39

glomerular damage, tumors which erode the urinary tract anywhere along its length, kidney trauma, urinary tract stones, renal infarcts, acute tubular necrosis, upper and lower urinary tract infections, nephrotoxins, and physical stress and contamination. dysmorphic RBCs are found in glomerular disease where passage through abnormal glomerulus distorts the RBC shape

Question 40

Oval fat bodies

Answer 40

renal tubular epithelial cells that contain numerous fat droplets and exhibit a Maltese cross configuration by polarized light microscopy

Question 41

Where are casts formed

Answer 41

distal convoluted tubule or the collecting duct

Question 42

What are hyaline casts

Answer 42

composed primarily of a mucoprotein (Tamm-Horsfall protein) secreted by tubule cells. The Tamm-Horsfall protein secretion, forms hyaline casts in the distal collecting duct. Most casts are made of Tamm-Horsfall mucoprotein

Question 43

Factors favoring protein cast formation

Answer 43

low flow rate, high salt concentration, and low pH, all of which favor protein denaturation and precipitation, particularly that of the Tamm-Horsfall protein.

Question 44

Cylindroids

Answer 44

Protein casts with long, thin tails formed at the junction of Henle's loop and the distal convoluted tubule

Question 45

What are granular and waxy casts? Broad casts?

Answer 45

When cellular casts remain in the nephron for some time before they are flushed into the bladder urine, the cells may degenerate to become a coarsely granular cast, later a finely granular cast, and ultimately, a waxy cast They are derived from renal tubular cells and are seen in end stage chronic renal disease

Question 46

Telescoped urinary sediment and what cuases is

Answer 46

red cells, white cells, oval fat bodies, and all types of casts are found in more or less equal profusion. 1) lupus nephritis 2) malignant hypertension 3) diabetic glomerulosclerosis, and 4) rapidly progressive glomerulonephritis

Question 47

Causes of fatty casts

Answer 47

nephrotic syndrome

Question 48

Normal crystals and abnormal crystals

Answer 48

Normal: calcium oxalate, triple phosphate crystals and amorphous phosphates. Uncommon/abnormal: cystine crystals in urine of neonates with congenital cystinuria or severe liver disease, tyrosine crystals with congenital tyrosinosis or marked liver impairment, or leucine crystals in patients with severe liver disease or with maple syrup urine disease.