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Clinical Chemistry Practicum > Urinalysis > Flashcards

Urinalysis Flashcards

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1
Q

What is the requirements for specimen collection of urine?

A
  • Dry, clean, leak-proof container
  • Minimum of 10-15 mL volume
  • First morning collection is best
  • Properly labeled with a requisition form
  • Tested within 2 hrs* or refrigerated for up to 8 hrs (allow to return to R.T. before testing)
  • No testing on a sample older than 4 hours (unless collected in BD preservative tube)
  • No microscopy performed on refrigerated samples
  • Chemical preservatives can interfere with some of the tests i.e.. Formalin interferes with glucose, blood, leukocyte esterase
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2
Q

How long do BD tubes keep sample integrity for?

A

For up to 72 hours without refrigeration for urine chemical and microscopic analysis

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3
Q

What preservatives do BD tubes have?

A

A preservative of chlorhexidine, ethylparaben and sodium propionate

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4
Q

What is used for microscope slide examination of urine?

A

Kova slide

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5
Q

What is the principle of measurement of the NOVAS?

A

Combines dry-pad technology with an easy-to-use cassette test format

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6
Q

What is the principle of measurement of the ADVANTUS?

A
  • Dry chemistry reagent strips
  • Color change measured by reflectance photometry
  • Dual readings at reactive and reference wavelengths
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7
Q

How does time collection of urine affect pH?

A

It is more acidic in AM, more alkaline after meals

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8
Q

What happens if the pH of a sample is greater than 8?

A

Can assume the sample is old

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9
Q

What happens if the urine test pad lingers too long in the sample or is not blotted properly?

A

The acid buffer from the protein pad can contaminate the pH pad and cause a falsely low reading- as test pad is strongly buffered at pH of 3

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10
Q

Why would we look at pH in a urine sample?

A

Helps determine the type of crystals present in the sample (i.e. uric acid crystals will only be present if the pH is acidic).

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11
Q

What factors contribute to formation of casts in the kidney?

A
  • Larger than normal amounts of plasma proteins entering the tubules
  • Decreased pH
  • Decreased urinary flow rate (urinary stasis)
  • Increased urine concentration (increased specific gravity)
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12
Q

What conditions are hyaline casts seen in?

A
  • Glomerulonephritis
  • Strenuous exercise
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13
Q

What do cellular casts consist of?

A
  • Cellular casts consist of a uromodulin mucoprotein matrix containing RBCs or WBCs, renal tubular epithelial cells, or a mixture of these cell types.
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14
Q

Where are cellular casts produced?

A

Distal tubules

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15
Q

Where may white cell casts be seen?

A

They are associated with infection or inflammation of the nephron. WBC casts can be seen in cases of pyelonephritis and interstitial nephritis.

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16
Q

What does the presence of red cell casts mean?

A

The presence of red cell casts in the urine indicates bleeding into the nephron

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17
Q

What do RTE casts indicate?

A

These casts indicate tubular damage

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18
Q

What are granular casts composed of?

A

Cellular remnants and by-products of protein degradation

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19
Q

What are waxy casts seen in?

A
  • Stasis of urine flow
  • Chronic renal failure
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20
Q

What are fatty casts indicative of?

A
  • Nephrotic syndrome
  • Toxic tubular necrosis
  • Diabetes mellitus
  • Crush injuries
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21
Q

What is a UTI/CYSTIS infection?

A

An infection of the lower urinary system. Most involve bladder and urethra

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22
Q

What is a PYELONEPHRITIS infection?

A

It is an infection of the upper urinary system, can be acute or chronic

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23
Q

What can be seen in the urinalysis of acute polynephritis?

A

Mild proteinuria, positive nitrate, numerous WBCs, RBCs, bacteria; WBC and bacterial casts, transitional and RTE cells

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24
Q

What can be seen in the urinalysis of chronic polynephritis?

A

Similar to acute pylonephritis. As disease progresses: renal concentration is decreased, increased proteinuria, hematuria; granular, waxy and broad casts

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25
Q

What is an acute PYELONEPHRITIS infection?

A

Bacterial invasion of the renal parenchyma by ascending from the lower urinary tract due to incomplete bladder emptying which can be due to the bacterial invasion of the bloodstream

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26
Q

What is Glomerulonephritis?

A

Sterile, inflammatory process in glomerulus and is associated with the finding of blood, protein, and casts in the urine

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27
Q

What can be seen in the urinalysis of Glomerulonephritis?

A

Marked hematuria, proteinuria; RBC, hyaline and granular casts (broad casts in chronic glomerulonephritis), dysmorphic RBCs and WBCs

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28
Q

What can be seen in the urinalysis of nephrotic syndrome?

A

Marked proteinuria, urinary fat droplets, oval fat bodies, RTE; epithelial, hyaline,fatty and waxy casts; microscopic hematuria, may have cholesterol crystals

29
Q

What is nephrotic syndrome?

A

Non-specifickidney disorder with marked proteinuria, low levels of serum albumin and high serum lipids

30
Q

What causes falsely alkaline pH?

A

> 8 = improper storage (urease producing bacteria; urea- ammonia)

31
Q

What causes falsely acidic pH?

A

Prolonged dipping or not blotted properly

32
Q

What causes false positives for glucose?

A

Oxidizing agents or detergents

33
Q

What causes false negatives for glucose?

A
  • Improper storage (glycolysis by bacteria)
  • High ketone levels
  • High SG
  • Low temp
34
Q

What are false positives for ketones?

A
  • Drugs with sulfhydryl groups
  • Red pigments
35
Q

What are false negatives for ketones?

A

Improper storage –> evaporation or breakdown by bacteria

36
Q

What can an alkaline pH correlate with?

A

Urinary tract infection

37
Q

What can ketones correlate with?

A
  • Glucose with diabetes
  • May also be due to excess vomiting or starvation
38
Q

Can can Proteinuria correlate with?

A
  • RBC, WBC in urine
  • Nephrotic Syndrome
39
Q

What are false postives for protein?

A
  • Semen contamination
  • Prolonged dipping
  • Highly buffered alkaline urine
  • High SG
  • Pigmented specimens
40
Q

What are false negatives for protein?

A
  • Proteins present other than albumin
41
Q

What are false positives for bilirubin?

A

Pigments from certain drugs

42
Q

What are false negatives for bilirubin?

A
  • Improper storage (light exposure)
  • Ascorbic acid or nitrite in high concentrations (due to diazo reaction)
43
Q

What conditions are bilirubin be positive?

A

Post hepatic jaundice, bile duct obstruction, liver damage

44
Q

Why are bacterial casts clinically significant?

A
  • Pyelonephritis
45
Q

What conditions can RBC casts be seen in?

A
  • Glomerulonephritis
  • Strenuous exercise
46
Q

What condition do RTE cells suggest?

A

Renal tubular damage

47
Q

What are granular casts indicative of?

A
  • Glomerulonephritis
  • Pyelonephritis
  • Stress and exercise
48
Q

What are broad casts indicative of?

A
  • Extreme urine stasis
  • Renal failure
49
Q

What are false positives for urobilinogen?

A

Highly pigmented urine

50
Q

What are false negatives for urobilinogen?

A
  • Formalin as a preservation
  • High concentrations of ascorbic acid or nitrite (diazo interference)
51
Q

What does Nitrite screen for?

A

UTI

52
Q

What are false positives for nitrite?

A
  • Improper storage
  • Highly pigmented urines
53
Q

What are false negatives for nitrite?

A
  • When there is a UTI but this test is negative (see next slide)
  • Ascorbic acid (diazo)
  • High SG
54
Q

What are false positives for leukocytes?

A
  • Oxidizing agents
  • Contamination with vaginal discharge
  • Highly pigmented urines
  • Formalin
55
Q

What are false negatives for leukocytes?

A
  • High SG (WBC’s don’t lyse)
  • High concentration of Protein, Glucose, Ascorbic acid, and Oxalic Acid
  • WBC’s are lymphocytes, not neutrophils
  • Unmixed sample
  • Antibiotics
56
Q

What are false positives for blood?

A
  • Menstrual contamination
  • Myoglobin (Heme molecule)
  • Oxidizing agents or detergents (Bleach)
  • Bacterial peroxidases
57
Q

What are false negatives for blood?

A
  • High SG (cells won’t lyse on contact with the test pad)
  • Ascorbic acid (manufacturers correct for this)
  • Unmixed specimens
  • Formalin, captopril, nitrite
58
Q

What is specific gravity?

A

The ratio of the density of a substance to the density of a reference substance

59
Q

When are ammonium biurate crystals found?

A

Encountered in old specimens and may be associated with the presence of the ammonia produced by urea-splitting bacteria

60
Q

When are calcium oxalate crystals found?

A

Can be found in fresh urine or in people who consume foods rich in oxalic acid such as asparagus, tomatoes etc.

61
Q

When are uric acid crystals found?

A

Associated with increased levels of purines and nucleic acids and are seen in patients with leukemia who are receiving chemotherapy, and sometimes in patients with gout.

62
Q

When are calcium monhydrate crystals found?

A

Ethyl glycol poisoning (anti-freeze)

63
Q

When are triple phosphate crystals found?

A

No clinical significance; however, they are often seen in highly alkaline urine associated with the presence of urea- splitting bacteria.

64
Q

When are cystine crystals found?

A

In the urine of persons who inherit a metabolic disorder called cystinuria

65
Q

When are cholesterol crystals found?

A

Associated with disorders producing lipiduria, such as the nephrotic syndrome, and are seen in conjunction with fatty casts and oval fat bodies.

66
Q

When are bilirubin crystals found?

A

Present in hepatic disorders producing large amounts of bilirubin in the urine

67
Q

When are sulfonamide crystals found?

A
  • Inadequate patient hydration
  • Tubular damage if crystals are forming in the nephron.
68
Q

When are tyrosine crystals found?

A

Found in acidic urine, and they may be caused by metabolic disorders like liver disease

69
Q

When are leucine crystals found?

A

Usually symptom of severe liver disease

Clinical Chemistry Practicum (5 decks)

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