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Liz's Urinalysis > Biochemical Testing of Urines > Flashcards

Biochemical Testing of Urines Flashcards

1
Q

How should you store reagent strips?

A
  • Avoid exposure to moisture, chemicals, heat, and light
  • Store at room temp below 30°C, but don’t freeze or refrigerate
  • Keep dessicant packet inside bottle, and close vial immediately after use
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2
Q

When should QC be performed on the reagent strips?

A
  • Use both pos and neg controls a minimum of once every 24 hours
  • When a new bottle of strips is opened
  • When a new lot is received
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3
Q

What is the normal specific gravity?

A

1.003-1.030

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4
Q

Urine w/ a specific gravity of 1.010

A

Isosthenuria

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5
Q

Urine w/ a specific gravity of < 1.010

A

Hyposthenuric

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6
Q

What is the most common cause of hyposthenuria?

A

Diabetes insipidus or renal disease

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7
Q

Urine w/ a specific gravity > 1.010

A

Hypersthenuric

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8
Q

Limitation of specific gravity

A

Only determines specific gravity from 1.000-1.030 on 0.005 increments

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9
Q

What lowers the specificity gravity

A

Highly buffered alkaline urine lowers readings

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10
Q

How do you correct for alkaline urine?

A

When pH is ≥ 7 add 0.005 to the strip reading if it is being read manually

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11
Q

What is specific gravity NOT affected by?

A
  • Radiographic dyes

- Increased glucose, urea, or protein

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12
Q

Principle of pH

A

Double indicator of methyl red and bromthymol blue

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13
Q

Reference range for pH

A

There isn’t a reference range for urine pH b/c broad variances occur daily in normal patients; will measure from 5.0-9.0 w/ 1.0 or 0.5 increments

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14
Q

When is acidic urine common during the day?

A

Morning (5.0-6.0)

- Urine below 5.0 is suspicious of tampering

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15
Q

When is alkaline urine suspicious of improper storage or tampering?

A

pH > 8.0

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16
Q

Meats and high protein diet lead to what pH in the urine?

A

Acidic urine

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17
Q

Vegetarian diet leads to what type of pH in the urine?

A

Alkaline urine

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18
Q

What is it called when you have basic urine after a large meal?

A

Alkaline tide

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19
Q

Condition where HCO3- is not reabsorbed and H+ are not excreted; leads to ACIDIC blood and ALKALINE urine?

A

Renal tubular acidosis

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20
Q

What cells contain leukocyte esterase?

A
  • Granulocytes (neutrophils, eosinophils, basophils, and monocytes)
  • Not found in RBCs, lymphocytes, and epis
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21
Q

Principle of leukocyte esterase test

A

Indoxylcarbonic acid ester → leukocyte esterase → indoxyl + diazonium salt → purple azodye

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22
Q

Leukocyte esterase is associated w/ what infections?

A
  • Bacterial

- Trichomonas

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23
Q

In bacterial infections w/ a positive leukocyte esterase, what result usually accompanies it?

A

Positive nitrite rxn

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24
Q

Positive leukocyte esterase may be found w/o bacteriuria in what 4 conditions?

A
  • Trichomonas
  • Chlamydia
  • Yeast infections
  • Inflammation of renal tissues
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25
Q

What is the specificity of leukocyte esterase?

A

Specific for esterase

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26
Q

What causes false positive for leukocyte esterase?

A
  • Vaginal contamination

- Medications that falsely color urine

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27
Q

What causes false negatives for leukocyte esterase?

A
  • ↑ glucose > 3 g/dL
  • ↑ protein > 500 mg/dL
  • High specific gravity
  • Certain medications
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28
Q

Principle of nitrite test

A

Greiss rxn

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29
Q

Clinical significance of nitrites

A

Bacteria convert nitrates into nitrites. Nitrites are an ABNORMAL finding

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30
Q

Nitrites indicates the presence of what?

A

GN bacteria

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31
Q

Bacterial infection that backflows from the bladder to the ureters and kidneys?

A

Pyelonephritis

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32
Q

What causes false positives for nitrite?

A
  • Falsely colored urine

- Improper storage allowing for bacterial proliferation?

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33
Q

What causes false negatives for nitrite?

A
  • Ascorbic acid (vitamin C)

- The enzyme is only found in GN bacteria (Enterobacteriaceae is the leading cause of UTIs)

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34
Q

Principle of proteins test

A

Protein error of indicators

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35
Q

What protein is primarily tested?

A

Albumin

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36
Q

Proteinuria is an indicator of ____ ____ and is often the very first indicator

A

Renal disease

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37
Q

Reference range of protein

A

Varies 1-14 mg/dL (150 mg/dL) is ok, but > 30 mg/dL is considered clinical proteinuria

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38
Q

Seven general reasons for protein in the urine

A
  • Glomerular damage
  • ↑ glomerular pressure (exercise
  • ↓ tubular reabsorption
  • Fanconi’s syndrome (PCT)
  • Orthostatic/postural proteinuria
  • Overflow proteinuria
  • Benign causes
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39
Q

Protein

- Causes of glomerular damage → proteinuria

A
  • Amyloidosis
  • Toxic substances
  • SLE (immune complexes)
  • Streptococcal glomerulonephritis (immune complexes)
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40
Q

Protein

- Causes of increased glomerular pressure → proteinuria

A
  • Exercise
  • Dehydration
  • Hypertension
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41
Q

Cause of decreased tubular reabsorption → proteinuria

A
  • Toxic substances
  • Viral infections
  • Fanconi’s syndrome (damages to proximal tubules)
42
Q

Describe rthostatic/postural proteinuria and best urine specimens to collect

A
  • Standing puts pressure on renal vein which leads to protein in the urine but laying down relieves the pressure.
  • Best to collect day and night time urine specimens
43
Q

Conditions that lead to PRE-RENAL overflow proteinuria

A
  • Septicemia (acute phase reactants)
  • Hemolytic episode (hemoglobinuria)
  • Muscle injury (myoglobinuria)
  • Immunoglobulins (Bence-Jones proteins)
44
Q

Conditions that lead to POST-RENAL overflow proteinuria

A
  • Inflammations due to bacterial or fungal infections
  • Presence of blood
  • Prostatic fluid or sperm
45
Q

Benign causes of proteinuria

A
  • Exposure to the cold
  • Exercise
  • Dehydration
  • Fever
46
Q

Protein sensitivity on Chem strip

A

6 mg/dL albumin

47
Q

What causes false negatives for protein?

A

Strips detect albumin, proteins other than that may not be detected

48
Q

What causes false positives for protein?

A
  • Very alkaline urines ( > 9 mg/dL)

- High specific gravity

49
Q

Albumin present in the urine below the detectable limits of a routine urine strip

A

Microalbuminuria

50
Q

Principle for detecting microalbumenuria

A

Uses sensitive dye-binding rxn that is specific for albumin

51
Q

A test that is used to confirm the presence of protein (esp. in alkaline urine)

A

Sulfosalicyclic acid (SSA)

52
Q

Principle of SSA

A

Cold precipitation test

53
Q

Describe the cold precipitation test

A
  • Protein will precipitate in the solution when SSA is added to produce a cloudy specimen
  • It will precipitate all proteins (not just albumin)
54
Q

What will excess protein present look like when shaken?

A

Foamy when shaken

55
Q

What is the most common test performed on urine and why?

A

Glucose! B/c of its importance in detection and monitoring of patients

56
Q

Principle of testing glucose

A

Double sequential enzyme rxn

57
Q

Renal threshold for glucose

A

180 mg/dL

58
Q

Hyperglycemic patients will present w/ glycosuria. What patients are these?

A
  • Diabetes and gestational diabetes

- Conditions: pancreatitis, Cushing’s syndrome, hyperthyroidism (opposes fxn of insulin leading to hyperglycemia)

59
Q

What causes patients w/ normal glucose levels to still present w/ glycosuria?

A
  • Damage to tubules that hinders reabsorption
  • Occurs in end stage real disease
  • Osteomalacia
  • Fanconi’s syndrome
  • ↓ reabsorption threshold in pregnancy
60
Q

What causes false positives for glucose?

A

Oxidizing agents

61
Q

What causes false negatives for glucose?

A
  • Ascorbic acid
  • High ketones
  • High specific gravity
  • Drugs
62
Q

What test should e performed for patients < 2 years old to detect reducing sugars other than glucose?

A

Clinitest

63
Q

What is a pathological condition that can lead to severe mental retardation, liver dysfunction, and cataracts?

A

Galactosemia

64
Q

Limitation of the clinitest

A
  • Not as specific or sensitive as glucose strips

- Man interfering reducing substances (ascorbic acid, drugs)

65
Q

What is in the highest concentration in a patient who is oxidizing fatty acids?

A

Beta-hydroxybutyrate

66
Q

Principle of the ketones test

A

Acetoacetate + sodium nitroprusside → purple color

67
Q

Ketonemia and ketonuria occurs when the body metabolizes _____ _____ due to inadequate amounts of _______

A

Fatty acids; CHOs

68
Q

Three general reasons for ketonemia

A
  • Inability to use carbohydrates (type 1/gestational diabetes)
  • Inadequate intake of carbs (starvation/diets)
  • Loss of CHOs (vomiting/starvation/dieting=Atkins diet)
69
Q

Ketone testing specificity is primarily sensitive to ____

A

Acetoacetate

70
Q

What causes false positives for ketones?

A

Drugs that contain sulfhydryl groups

71
Q

What causes false negatives for ketones?

A
  • Improper storage and handling
  • Improper storage of strips
  • Uncapped specimens
  • Acidosis
72
Q

Principle of urobilinogen test (2 methods)

A
  • Multistix (Ehrlich’s rxn)

- Chemstrip (Diazo rxn)

73
Q

Urobilinogen
- What is the increased production of bilirubin leading to increased urobilinogen produced and consequently increased urobilinogen in urine

A

Prehepatic mechanism

74
Q

Urobilinogen

- What conditions lead to prehepatic urobilinogen?

A
  • Hemolytic anemia
  • Sickle cell
  • Hereditary spherocytosis
  • Thalassemia
  • Pernicious anemia
  • Txn rxns
75
Q

Urobilinogen
- What is it when a damaged liver is not capable of reabsorping urobilinogen from the portal circulation leading to additional urobilinogen entering the blood stream?

A

Hepatic mechanism

76
Q

Urobilinogen

- Conditions that may cause hepatic urobilinogen?

A
  • Hepatitis

- Cirrhosis

77
Q

Urobilinogen
- What is it called when conjugated bilirubin will not be able to enter the intestine due to blockage in the bile duct leading to no urobilinogen production?

A

Post-hepatic mechanism

78
Q

What causes false positives for urobilinogen?

A
  • p-aminosalicylic acid

- Sufamethoxazol

79
Q

What causes false negatives for urobilinogen?

A
  • Exposure to light

- High nitrites

80
Q

Principle of bilirubin test

A

Diazo rxn

81
Q

What test has greater sensitivity to bilirubin?

A

Ictotest

82
Q

In what mechanism is bilirubin negative?

- Provide examples

A

Prehepatic mechanism

  • Hemolytic disease-like txn rxns
  • Hemolytic anemia
83
Q

In what mechanism does conjugated bilirubin “leak” from damaged hepatocyte back into the blood, thus increasing bilirubin?
- Provide examples

A

Hepatic mechanism

  • Hepatitis
  • Cirrhosis
84
Q

In what mechanism is conj bilirubin unable to pass though the bile duct and thus back up not the liver and bloodstream leading to bilirubin in the urine?
- Provide examples

A

Post-hepatic mechanism

- Bile duct blockage

85
Q

Bilirubin and urobilinogen

- Which one (or both) is positive in prehepatic (hemolytic disesase)?

A
  • Bilirubin: negative

- Urobilinogen: positive

86
Q

Bilirubin and urobilinogen

- Which one (or both) is positive in hepatic (liver damage)?

A
  • Bilirubin: positive

- Urobilinogen: positive

87
Q

Bilirubin and urobilinogen

- Which one (or both) is positive in posthepatic (bile duct obstruction)?

A
  • Bilirubin: positive

- Urobilinogen: negative

88
Q

What causes false positives in bilirubin?

A
  • pH > 9.0

- Some medications

89
Q

What causes false negatives in bilirubin?

A
  • Ascorbic acid
  • High nitrites
  • Improper storage
90
Q

Blood

- What all does it detect?

A
  • Hemoglobin
  • Intact RBCs
  • Myoglobin
91
Q

Principle of the blood test

A

Based off of the peroxidase-like activity of hemoglobin

92
Q

Blood

  • What is hematuria?
  • Clarity?
A
  • Hematuria → intact red cells in the urine

- Clarity → cloudy (RBCs seen microscopically)

93
Q

Blood

- What causes hematuria?

A
  • Trauma
  • Renal calculi
  • Advanced glomerular damage
  • Infection
  • Neoplasms
94
Q

Blood

  • What is hemoglobinuria?
  • Clarity?
  • Color?
  • What should you look for?
A
  • Hemoglobinuria → hgb in the urine
  • Clarity → usually clear
  • Color → yellow to red to brown
  • Should look for hemosiderin granules
95
Q

Blood

- Hemoglobinuria is caused by what?

A

Associated w/ hemolysis

  • Hemolytic disease
  • Poisoning
  • Burns
  • Txn rxn
  • Paroxysmal nocturnal hemoglobinuria (PNH)
96
Q

Blood

  • What is myoglobinuria?
  • Clarity?
  • Color?
A
  • Myglobinuria → myoglobin in the urine
  • Clarity → clear
  • Color → reddish brown
97
Q

Blood

- Myoglobinuria is caused by what?

A

Associated w/ muscle destruction

  • Traumatic accidents
  • Alcoholism or drug use
  • Muscle wasting disease
98
Q

What causes false positives when testing for blood?

A
  • Menstrual contamination

- Microbial peroxidases

99
Q

What causes false negatives when testing for blood?

A
  • Ascorbic acid
  • Unmixed specimens
  • High specific gravity leading to crenated RBCs
100
Q

What situation makes it impossible to interpret a reaction?

A

In highly color urine from medications or pigments from certain foods

101
Q

What is the purpose of the ictotest?

A

Confirmatory test for bilirubin

Liz's Urinalysis (6 decks)

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