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MT > STRASINGER (7TH ED. | CHAPTER 6: CHEMICAL EXAMINATION OF URINE) > Flashcards

STRASINGER (7TH ED. | CHAPTER 6: CHEMICAL EXAMINATION OF URINE) Flashcards

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1
Q

What are the (10) parameters that are measured by current commercial reagent strips?

A
  1. pH
  2. Protein
  3. GLU
  4. Ketones
  5. Blood
  6. Bilirubin
  7. Urobilinogen
  8. Nitrite
  9. Leukocytes
  10. SG
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2
Q

What are the (2) trade names of the (2) major types of reagent strips?

A
  1. Multistix (Siemens Healthcare Diagnostics, Inc., Tarrytown, NY)
  2. Chemstrip (Roche Diagnostics, Indianapolis, IN)
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3
Q

What are consist of chemical-impregnated absorbent pads attached to a plastic strip?

A

Chemical reagent strips

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4
Q

When does a color-producing chemical reaction takes place in reagent strips?

A

When the absorbent pad comes in contact w/ urine

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5
Q

How are the reactions in reagent strips interpreted?

A

By comparing the color produced on the pad within the required time frame w/ a chart supplied by the manufacturer

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6
Q

What are the (5) semiquantitative values that are used when interpreting reactions in reagent strips?

A
  1. Trace
  2. 1+
  3. 2+
  4. 3+
  5. 4+
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7
Q

True or False

Automated reagent strip readers do not provide Systéme International (SI) units

A

False, automated reagent strip readers also provide Systéme International (SI) units

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8
Q

What is the methodology / process (/ what are the steps) of reagent strip technique?

A
  1. Dip the reagent strip completely, but briefly, into a well-mixed specimen at room temperature
  2. Remove excess urine from the strip by running the edge of the strip on the container when withdrawing it from the specimen
  3. Blot the strip horizontally on an absorbent medium
  4. Wait for the specified length of time for reactions to take place according to the manufacturer
  5. Compare the colored reactions against the manufacturer’s chart using a good light source

Another process:
1. Dip the reagent strip briefly into a well-mixed uncentrifuged urine specimen at room temperature
2. Remove excess urine by touching the edge of the strip to the container as the strip is withdrawn
3. Blot the edge of the strip on a disposable absorbent pad
4. Wait the specified amount of time for the reaction to occur
5. Compare the color reaction of the strip pads to the manufacturer’s color chart in good lighting
6. Read the results at the correct time, and record the results

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9
Q

What are the (8) errors caused by improper reagent strip technique?

A
  1. Formed elements, such as RBCs and WBCs sink to the bottom of the specimen and will be undetected in an unmixed specimen
  2. Allowing the strip to remain in the urine for an extended period may cause leaching of reagents from the pads
  3. Allowing excess urine to remain on the strip after its removal from the specimen can produce a runover between chemicals on adjacent pads, producing distortion of the colors
  4. The timing for reactions to take place varies between tests and manufacturers and ranges from 30 - 120 secs for leukocyte esterase (LE)
  5. A good light source is essential for accurate interpretation of color reactions
  6. The strip must be held close to the color chart w/out actually being placed on the chart
  7. Reagent strips and color charts from different manufacturers are not interchangeable
  8. Specimens that have been refrigerated must be allowed to return to room temperature before reagent strip testing, as the enzymatic reactions on the strips are temperature dependent
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10
Q

What is the recommended solution to prevent runover between chemicals on adjacent pads in the reagent strip?

A

Blot the edge of the strip on absorbent paper and hold the strip horizontally while comparing it w/ the color chart

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11
Q

What should be done to obtain best semiquantitative results via reagent strips?

A

Follow the manufacturer’s stated time

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12
Q

When precise timing of reading results via reagent strips cannot be achieved, what should be done?

A

The manufacturers recommend that reactions be read between 60 - 120 secs, w/ the LE reaction read at 120 secs

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13
Q

True or False

Manufacturers have a constant direction of the reagent strip to the color chart on the container when reading results

A

False, manufacturers vary in the direction of the reagent strip to the color chart on the container when reading results

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14
Q

True or False

Automated reagent strip instruments standardize the color interpretation and timing of the reaction and are not subject to room lighting deficiencies or inconsistency among laboratory personnel

A

True

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15
Q

True or False

The enzymatic reactions on the strips are not dependent to temperature

A

False, the enzymatic reactions on the strips are temperature dependent

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16
Q

Reagent strips must be protected from deterioration caused by what (4) components?

A
  1. Moisture
  2. Volatile chemicals
  3. Heat
  4. Light
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17
Q

How to protect reagent strips from light and moisture?

A

They are packaged in opaque containers w/ desiccant

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18
Q

When are reagent strips removed from the bottle?

A

They are removed just before testing and the bottle is tightly resealed immediately

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19
Q

True or False

Bottles (of reagent strips) can be opened in the presence of volatile fumes

A

False, bottles (of reagent strips) should not be opened in the presence of volatile fumes

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20
Q

What is the storage temperature recommended by manufacturers for reagent strips?

A

Room temperature below 30°C (but never refrigerated)

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21
Q

All bottles (reagent bottles) are stamped w/ an expiration date, what is the function of this?

A

This represents the functional life expectancy of the chemical pads

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22
Q

Can reagent strips be used if past the expiration date?

A

No

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23
Q

Can the chemical pads (in the reagent strips) be touched when removing the strips?

A

No

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24
Q

What should be done to reagent strips (even if they are still within the expiration date)? What is the purpose of doing this?

A

Visual inspection should be done each time a strip is used to detect deterioration

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25
How to perform the **quality control** of **reagent strips**?
Check w/ both (**+**) and (**-**) controls (according to the frequency established by the lab policy)
26
When do many labs perform **QC** of reagent strips w/ both (**+**) and (**-**) controls?
In the **beginning** of each shift
27
What are the (3) situations where **QC** of reagent strips are done?
1. When a **new bottle** of reagent strips is opened 2. When **questionable** results are obtained 3. When there is a concern about the **integrity** of the strips
28
What should be done to all **QC results**?
Must be **recorded** following lab protocol
29
Is **distilled water** recommended as a (**-**) control for **QC** of reagent strips? Why or why not?
**No**, because reagent strip chemical reactions are designed to perform at **ionic** concentrations similar to **urine**
30
What should be the **QC** results of reagent strips?
All readings of (**-**) control = (**-**) All readings of (**+**) control = agree w/ **published** value
31
What should be done if **QC** results does **not** agree w/ published values?
Testing of additional **strips** and **controls**
32
Demonstration of chemically acceptable reagent strips does **not** entirely rule out the possibility of **inaccurate** results, what are the other (3) factors that can also produce **errors**?
1. **Interfering** substances in the urine 2. **Technical carelessness** 3. **Color blindness**
33
What are the (3) information that the reagent strip manufacturers have published which the lab personnel should be **aware** of?
1. **Limitations** i. **Interfering** substances of chemical reactions ii. **Sensitivities** of chemical reactions
34
Provide (1) primary example of reagent strip **interference**
**Masking** of the color reactions by the **orange** pigment present in the urine of patients who are taking **phenazopyridine** compounds
35
What are procedures using **different reagents** or **methodologies** to detect the **same substances** as detected by the reagent strips with the **same** or **greater sensitivity** or **specificity**?
**Confirmatory** tests
36
**True or False** **Nonreagent** strip testing procedures using **tablets** and **liquid** chemicals may be available when **questionable** results are obtained or **highly pigmented** specimens are encountered. In the past, many of these procedures were used routinely to **confirm** (**+**) results
**True**
37
The chemical reliability of nonreagent strip testing procedures must be checked using what (2) controls?
1. (**+**) controls 2. (**-**) controls
38
What are the (10) parameters (reagent **strip** testing) of **chemical** examination of urine?
1. **pH** 2. **Protein** i. **Prerenal** proteinuria ii. **Renal** proteinuria a. **Microalbuminuria** b. **Orthostatic** (**postural**) proteinuria c. **Tubular** proteinuria iii. **Postrenal** proteinuria 3. **GLU** 4. **Ketones** 5. **Blood** i. **Hematuria** ii. **Hemoglobinuria** iii. **Myoglobinuria** 6. **Bilirubin** 7. **Urobilinogen** 8. **Nitrite** 9. **Leukocyte esterase** (**LE**) 10. **SG**
39
What are the (2) organs that are the major **regulators** of the **acid-base** content in the body?
1. **Lungs** 2. **Kidneys**
40
How does the lungs and kidneys **regulate** the **acid-base** content in the body?
**Lungs** = **secretion** of **hydrogen** (in the form of **ammonium** ions), **hydrogen phosphate**, and **weak organic acids** **Kidneys** = **reabsorption** of **bicarbonate** (from the **filtrate** in the **convoluted tubules**)
41
What is the **pH** of the **first morning** urine of a **healthy** individual?
Slightly **acidic** (**5.0 - 6.0**)
42
What is the pH of the urine of patients **after** a **meal**? What is this phenomena called?
More **alkaline** pH | **alkaline tide**
43
What is the pH of **normal random** urine?
**4.5 - 8.0**
44
What are the pH of the following urine: 1. **First morning** urine (of a **healthy** individual) 2. **After** a **meal** (**alkaline tide**) 3. **Normal random** urine
1. **5.0 - 6.0** 2. More **alkaline** 3. **4.5 - 8.0**
45
What are the (5) information that should be considered in terms of **urinary pH**?
1. **Acid-base** content of the blood 2. **Renal function** 3. Presence of **UTI** 4. **Dietary** intake 5. **Age** of specimen
46
What are the (11) causes of **acid** urine?
1. **Emphysema** 2. **DM** 3. **Starvation** 4. **Dehydration** 5. **Diarrhea** 6. Presence of **acid**-producing bacteria (**Escherichia coli**) 7. High-**protein** diet 8. **Cranberry juice** 9. **Medications** i. **Methenamine mandelate** (**Mandelamine**) ii. **Fosfomycin tromethamine** (**Monurol**)
47
What are the (6) causes of **alkaline** urine?
1. **Hyperventilation** 2. **Vomiting** 3. **Renal tubular acidosis** (**RTA**) 4. Presence of **urease**-producing bacteria 5. **Vegetarian** diet 6. **Old** specimens
48
What are the (2) **clinical significance** of urinary **pH**?
1. Aid in determining the existence of **systemic acid-base disorders** of **metabolic** or **respiratory** origin 2. Management of urinary **conditions** that require the urine to be maintained at a specific **pH**
49
What is the **pH** of urine in cases of **respiratory** or **metabolic acidosis** (which are **not** related renal function disorders)?
**Acidic**
50
What is the **pH** of urine in cases of **respiratory** or **metabolic alkalosis**?
**Alkaline**
51
What may be the other conditions of the patient if his/her urinary pH is **acidic** or **alkaline** (aside from **respiratory** or **metabolic acidosis** and **respiratory** or **metabolic alkalosis**, respectively)?
May be a disorder caused by the kidney's **inability** to **secrete** or **reabsorb acid** or **base**
52
What is the cause of formation of **urinary crystals** and **renal calculi**?
**Precipitation** of **inorganic** chemicals **dissolved** in the urine
53
How to prevent the precipitation of **inorganic** chemicals dissolved in the urine which can lead to urinary crystals and renal calculi? Provide an example
Maintain the urine at a pH that is **incompatible** with the **precipitation** of the particular chemicals causing the calculi formation Example: **Calcium oxalate** (a frequent constituent of renal calculi) precipitates primarily in **acidic** and not alkaline urine. Therefore, maintaining urine at an alkaline pH **discourages** formation of the calculi
54
What is the importance of urinary **pH**?
Knowing the pH of urine is important in the identification of **crystals**
55
What is an important way in treating **UTIs** caused by **urea-splitting** organisms? How? Why?
Maintaining an **acidic** urine, because they do **not** multiply as readily in an acidic medium Because these organisms are responsible for the **highly alkaline** pH found in specimens that have been allowed to sit **unpreserved** for extended periods
56
What are the (2) factors that can **control** the **pH** of urine?
1. **Dietary regulation** (**primary**) 2. **Medications**
57
What is the difference of **pH** between individuals on **high-protein** and **high-meat** diets vs **vegetarians**?
**High-protein** and **high-meat** diets = **acidic** urine **Vegetarians** = **more alkaline** urine
58
Why is the **pH** of urine of **vegetarians** **more alkaline** compared to individuals on high-protein and high-meat diets?
Because after the digestion of many **fruits** and **vegetables**, **bicarbonate** forms
59
Being a vegetarian causes pH of urine to become more alkaline, however, what is the **pH** of urine of patients who consume **cranberry juice** or **supplements**?
**Acidic**
60
What is the use of consuming **cranberry juice** or **supplements**? Why?
Home **remedy** for **minor** bladder infections, because cranberry juice or supplements **inhibit** the colonization of certain urinary pathogens Hence, people who are **prone** to frequent UTIs are often advised to drink **cranberry juice** or take over-the-counter **cranberry pills**
61
What are the (2) **medications** prescribed for UTIs? What is the mechanism of these medications?
1. **Methenamine mandelate** (**Mandelamine**) 2. **Fosfomycin tromethamine** (**Monurol**) These medications are **metabolized** to produce an **acidic** urine
62
What is the **pH** of **freshly** excreted urine (in **normal** or **abnormal** conditions)?
Does **not** reach above **8.5**
63
What is the clinical significance if the **pH** of urine is above **8.5**? What should be done if the pH of urine is above 8.5?
The specimen is **improperly** preserved, hence, a **fresh** specimen should be obtained to ensure the **validity** of the analysis
64
What will happen if urine specimens are collected in containers other than **single-use** laboratory-supplied containers? What is the cause of this urinary pH?
pH of above **8.5**, if **alkaline detergent** remains in the container
65
**Multistix** and **Chemstrip** measure urine pH in what increments?
**0.5 - 1**-unit increments between pH **5 - 8.5 visually** and pH **5 - 9 instrumentally**
66
What is the principle of Multistix and Chemstrip reagent strips for **pH**? Explain
**Double-indicator system** (**methyl red** and **bromthymol blue**) **Methyl red** = **red** to **yellow** (pH of **4 - 6**) **Bromthymol blue** = **yellow** to **blue** (pH of **6 - 9**) pH of **5 - 9** = **orange** (pH **5**) to **yellow** and **green** to final **deep blue** (pH **9**) **Methyl red + H^+ -> bromthymol blue - H^+ (Red-orange -> yellow) (green -> blue)**
67
What are the substances that **interfere** with reagent strip reactions for **pH**?
**None**
68
What can cause interference in reagent strip reactions for **pH**? Why?
**Bacterial growth** (by certain organisms) which causes marked **alkaline** shift, usually because of **urea** conversion to **ammonia**
69
What will happen if there is a **runover** between **pH** pad and its adjacent pads?
**Highly acidic protein** (Multistix), as this may produce a reading that is **falsely acidic** in an alkaline urine
70
What are the (7) clinical significance of urine pH?
1. Respiratory or metabolic acidosis/ketosis 2. Respiratory or metabolic alkalosis 3. Defects in renal tubular secretion and reabsorption of acids and bases - renal tubular acidosis
71
Among the routine chemical tests, what is the most indicative of **renal disease**?
**Protein**
72
Often, **proteinuria** is associated with what?
**Early renal disease**
73
What is the **important** chemical test? Why?
**Protein**, because **proteinuria** is indicative of **early renal disease**
74
Does a **normal** urine contain **protein**? If yes, how much?
Yes, urine contains very little protein, usually **< 10 mg/dL** or **100 mg per 24 hrs** is excreted
75
Explain the very little amount of **protein** present in **normal** urine
Consists primarily of **low** molecular weight **serum** proteins that have been **filtered** by the glomerulus and proteins produced in the **genitourinary tract**
76
The very little amount of protein present in **normal** urine has a **low** molecular weight, due to this, what is the **major** serum protein found in normal urine?
**Albumin**
77
**True or False** Even though **albumin** is present in **high** concentrations in the **plasma**, the normal albumin content in **urine** is **low** because majority of albumin presented to the glomerulus is **not** filtered, and much of the filtered albumin is **reabsorbed** by the tubules
**True**
78
What are the **other** (5) proteins?
1. Small amounts of **serum** and **tubular microglobulins** 2. **Tamm-Horsfall protein** (THP) 3. Proteins from **prostatic** secretions 4. Proteins from **seminal** secretions 5. Proteins from **vaginal** secretions
79
**THP** is aka what?
**Uromodulin**
80
**THP** is **produced** by what?
**Renal tubular epithelial cells**
81
What is the more **recent** name for **THP**?
**Uromodulin**
82
What is **uromodulin**?
**Glycoprotein**
83
**Uromodulin** is **produced** routinely where?
**Ascending loop of Henle**
84
What forms the **matrix** of **casts**?
**Uromodulin**
85

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