3 Flashcards
What is a “dipstick” used for?
Basic diagnostic tool used to determine pathological changes in a patient’s urine in standard urinalysis
How long does it take before you can read a dipstick?
60-120 seconds after the dip
How do the plastic strips (dipstick) testing work?
Plastic strips have pad that contain chemicals that react with certain compounds in the urine producing a specific color. (Paper strips are specific to a single reaction)
For accurate dipstick results, what should you do?
Store reagent strips in their bottle with lid closed at room temperature, this prevents the loss of sensitivity of reagent strips
What should you not expose dipsticks to?
- Sunlight
- Heat
- Cold
- Volatile Substances
- Moisture
When using a dipstick, when should you test urine?
Test urine which is brought to room temperature and well-mixed urine
What would discoloration of the strip indicate?
Significant loss of reactivity
What do the kidneys and lungs regulate?
Acid-base balance of the body
The pH of the urine is a reflection of _____
The ability of the kidneys to maintain normal hydrogen ion concentration in plasma and extracellular fluid
What are the 2 main objectives of urine pH?
1) Diagnostic (e.g. metabolic abnormalities)
2) Therapeutic (e.g. regulation of diet or medications)
What does urine pH normally fluctuate between?
Acidic and Alkaline
Acid indicator =
Methyl Red
Alkaline Indicator =
Bromthymol blue
pH of urine ranges from ______
5.0 to 8.5** in half units (commercial dipstick)
When your protein intake is high, what happens on your urine dipstick?
More phosphates, sulfates are produced which results in more acidic urine
Vegetable diet normally results in urine pH of _____
> 6
What is the large list of factors that result in acidity?
- Dehydration
- Diarrhea
- Fever
- Diabetes Ketoacidosis
- Gout
- Pulmonary Emphysema
- High protein diets or cranberries
- Renal Tubular Acidosis (proximal tubular, distal tubular) metabolic acidosis
- Acidifying drugs (for ammonium magnesium stone prevention)
What is the long list of factors that result in alkalinity (urine)?
- Acute and chronic renal failure
- Urinary tract infections
- Bacterial contamination of urine
- Alkaline drugs
- Diuretics
What is the source of low molecular weight protein that could be found in the urine?
Genito-urinary tract
Describe Mucoprotein Tamm-Horsfall (T-H):**
It is secreted by the renal tubules (renal epithelial cells) and is not derived from blood plasma **
In regards to urine protein, what amount of T-H protein is excreted?**
Less than 150mg/24 hr (or 20mg/dL) **
What is T-H protein?
It is a matrix for formation of calculi or casts
When testing for protein in urine, what is the principle it is based on called?
“Protein Error of pH indicators” ***
What is Protein Error of pH indicators?
Ability of protein to alter the color of some acid-base indicators without altering the pH
In a solution void of protein, ______
Tetrabromphenol blue, buffered at a pH of 3, is yellow
In the presence of protein (albumin), what happens when testing urine protein?
The color changes to green, then blue, depending on the concentration
The method of “Protein Error of pH Indicators” is more sensitive to ______ *****
Albumin than to globulin ***
The principle, “Protein error of pH indicators”most common indicator?
Tetrabromphenol blue
Protein error of pH indicators detects primarily _____
albumin
What would a false positive in urine protein result from?
- Highly buffered alkaline urine (medications or old urine
- Prolonged exposure to the sample (too long)
- Container cleaning compounds (quaternary ammonia)
- Some skin cleaners
- blood in urine
What would a false negative in urine protein result from?
- Diluted urines
- Elevated amounts of proteins other than albumin
What factors could result in (temporary) proteinuria, (transient proteinuria, “trace”)? ***
- Strenuous exercise
- Postural Proteinuria
- Dehydration
- Exposure to heat or cold
- Fever
- Emotional stress
- Pregnancy
What are diseases that can cause persistent proteinuria?
- Glomerulonephritis
- Pyelonephritis
- Malignant hypertension
Urine glucose is normally contained where?
In glomerular Ultrafiltrate
Where is 100% of glucose reabsorbed?
In the proximal tubules
Urine glucose is usually not present unless threshold levels exceed ______
160-180 mg/dl **
The dipstick test is sensitive only to ____
GLUCOSE *, and other sugars do not give positive result
A false positive from urine glucose could develop from _____
After using oxidizing cleaning agents for urine containers:
- Peroxide
- Hypochlorite
A false positive of urine glucose occurs in patients taking what drug?
Levodopa (Parkinson’s Disease)
When high levels of _____ are present in urine, this can create a false positive when testing urine glucose
KETONES***
A false negative in testing urine glucose could develop in:
- Cool urine
- Urine with high specific gravity due to uricosuria
- Alkaline urine due to bacterial contamination of old urine
- Ascorbic acid (Vitamin C) in high doses can inhibit the enzymatic reaction
When glucose is present in urine 2 hours after a sweet food, what is it known as?
Transient Glucosuria ***
What is Glucosuria dependent on?
- Blood glucose levels
- Glomerular filtration rate
- Tubular Reabsorption
Where is glucosuria seen in ?
Diabetes Mellitus and Congenital forms of glucosuria
Where does PERSISTENT glucosuria develop in? ***
- Diabetes Mellitus
- CNS problems (stroke, neoplasms)
- Kidney problems (uremia)
- Endocrine problems (e.g. acromegaly, pheochromocytoma)
- Liver disorders (e.g. glycogen storage disease)
- Pharmaceutical agents (e.g. diuretics, birth control pills)
What is a second method for measurement of sugar in urine?
Clinitest
What does clinitest measure?
Glucose and other reducing sugars which may be present (using a tablet that is dropped into the urine in a test tube)
What would give a false positive for clinitest?
- Ascorbic acid
- Cephalosporins
- Probenecid (treating gout and hyperuricemia)
- Urinary preservatives: formalin and formaldehyde
What are the characteristics of Clinitest?
It is accurate and reliable test for reducing substances
- Technique errors
What is a Benedict’s test used to determine?
The presence of reducing sugars such as fructose, glucose, maltose, galactose, and lactose in urine
What is urine reducing sugar test?
It is a screening test for diagnosis of genetic disorders of carbohydrate metabolism
What test is routinely performed on urine for newborn children?
Urine reducing sugar test
What does urine reducing sugar test predominately detect (early screening)?
Galactosemia or diabetes ***
Where are ketones produced?
Normally by the liver as part of fatty acid metabolism
In normal states, urine ketones will be _____
completely metabolized
Describe why the body would create urine ketones:
If for any reason the body cannot get enough glucose for energy it will switch to using body fats, resulting in an increase in ketone production making them detectable in the blood and urine
Ketone bodies that commonly appear in the urine when fats are burned for energy are:
- Acetoacetic acid (20%)
- Beta-hydroxybutyric acid (78%)
- Acetone (2%) is lost in the air if a sample is left standing at room temperature
Urine should be tested ______ after collection of urine
immediately
Normally the urine should not contain a noticeable concentration of _____
Ketones to give a positive reading
In regards to urine ketones, the Dipstick test determines ____
The acetoacetic acid, or some brands of reagent strip also detects acetone
In regards to urine ketones, the dipstick doesn’t detect ____
Beta hydroxybutyric acid
In regards to urine ketones, what may give a false positive or atypical color?
- Highly pigmented urine
- Combination of high specific gravity and low pH***
- Dehydration
- Phenylketones
- Some medications
- Abscrobic acid
- Positive and questionable results may be confirmed with a tablet test
