Proper care of reagent strips should include:
1. Store with dessicant (amber) in an opaque container (not clear)
2. Do not use past expiration date
3. Do not expose to toxic fumes
4. Store below 30degrees but do not freeze
Several companies manufacture both positive and negative controls. Distilled water is not recommended as a negative control because ____
reagent strip chemical reactions are designed to perform at ionic concentrations similar to urine
What is the principle employed by the pH test using reagent strips?
double indicator reaction
The Multistix and Chemstrip brands of reagent strips measure urine pH in 0.5- or 1-unit increments between pH 5 and 9. To differentiate pH units throughout this wide range, both manufacturers use a doubleindicator system of methyl red and bromthymol blue. Methyl red produces a color change from red to yellow in the pH range 4 to 6, and bromthymol blue turns from yellow to blue in the range of 6 to 9. Therefore, in the pH range 5 to 9 measured by the reagent strips, one sees colors progressing from orange at pH 5 through yellow and green to a final deep blue
at pH 9.
Urine from vegetarians is more ____ (alkaline or acidic), owing to the formation of bicarbonate following digestion of many fruits and vegetables. An exception to the rule is ______
Acidic / cranberry juice
Persons on high-protein and high-meat diets tend to produce acidic urine, whereas urine from vegetarians is more alkaline, owing to the formation of bicarbonate following digestion of
many fruits and vegetables. An exception to the rule is cranberry juice, which produces an acidic urine and has long been used as a home remedy for minor bladder infections.
The pH of freshly excreted urine does not reach pH ___ in normal or abnormal conditions. A pH
of ____ is associated with an improperly preserved specimen and indicates that a fresh specimen should be obtained to ensure the validity of the analysis.
pH 9/pH 9
In the laboratory, a primary consideration associated with pH is: _____
The precipitation of inorganic chemicals dissolved in the urine forms urinary crystals and renal calculi. This precipitation depends on urinary pH and can be controlled by maintaining the urine at a pH that is incompatible with the precipitation of the particular chemicals
causing the calculi formation.
A urine specimen from a diabetic whose glucose is not under control will probably contain:
3. an increased specific gravity
Ketonuria shows a deficiency in insulin, indicating the need to regulate dosage. It is often an early indicator of insufficient insulin dosage in type 1 diabetes. Increased accumulation of ketones in the blood leads to electrolyte imbalance,
dehydration, and, if not corrected, acidosis and eventual diabetic coma.
Prerenal proteinuria is caused by conditions affecting the _____ and (is/is not) indicative of renal disease.
the plasma / is not
Prerenal proteinuria is caused by conditions affecting the plasma prior to its reaching the kidney and, therefore, is not indicative of actual renal disease.
A primary example of prerenal proteinuria is _____
secretion of Bence Jones protein by persons with multiple myeloma
Name some examples of prerenal proteinuria:
1. multiple myeloma (Bence Jones protein)
2. increased levels of low-molecular-weight plasma proteins such as hemoglobin, myoglobin, and the acute phase reactants associated with
infection and inflammation.
The test for protein using the reagent strip is most sensitive for ___
The SSA test is a precipitation test that reacts equally to all forms of protein
When using the reagent strip for protein, false positives may be caused by:
1. High alkaline urine
2. High specific gravity
3. Loss of buffer due to prolonged exposure of reagent strip to the specimen
The major source of error with reagent strips occurs with highly buffered alkaline urine that overrides the acid buffer system, producing a rise in pH and a color change unrelated to protein concentration. Likewise, a technical error of allowing the reagent pad to remain in contact with the urine for a prolonged period may remove the buffer. False-positive readings
are obtained when the reaction does not take place under acidic conditions.
When using the reagent strip for protein, false negatives may be caused by:
2. Proteins other than albumin
What are some possible causes of postrenal proteinuria:
1. urinary tract infection
2. Prostatic fluid
3. vaginal secretions
4. menstrual contamination
4 examples of renal proteinuria:
1. glomerular proteinuria
2. tubular proteinuria
3. orthostatic (postural) proteinuria
The principle for the reagent strip test is___
protein error of indicators
certain indicators change color in the presence of protein even though the pH of the medium remains constant. This is because protein (primarily albumin) accepts hydrogen ions from the indicator. The test is more sensitive to albumin because albumin contains more amino groups to accept the hydrogen ions than other proteins.
A protein that precipitates at 60 degrees F and dissolves at 100 degrees is associated with _____
Multistix pro has both protein-low reading and protein-high reading. Protein-low uses a ____ reaction and protein-high uses a ____
Protein-Low - dye binding
Protein-high - protein error of indicators
Onset of renal complications can be predicted by testing for ______ and the progression of renal disease can be prevented through better stabilization of _____
microalbuminuria / blood glucose levels
The _____ procedure is a specific test for glucose and the ______ is a general test for glucose and other reducing substances
glucose oxidase / copper reduction method
In a glucose reagent strip, what will cause a false positive:
1. Contamination by oxidizing agents (peroxide)
In a glucose reagent strip, what will cause a false negative:
1. ascorbic acid (high levels)
2. ketones (high levels)
3. High specific gravity
4. Low temperatures
5. Improperly preserved speciment
______ should be performed on newborns for ____
Clinitest (copper reduction test) / galactosuria (inborn error of metabolism)
Galactose in the urine of a newborn represents an "inborn error of metabolism" in which lack of the enzyme galactose-1-phosphate uridyl transferase prevents breakdown of ingested galactose and
results in failure to thrive and other complications, including death. All newborns should be screened for galactosuria because early detection followed by dietary restriction control the
Explain conflicting results between the Glucose Oxidase and Clinitest
The Clinitest is not as sensitive as the glucose oxidase test, so the finding of
a 1+ reagent strip reading and a negative Clinitest should not be surprising. A strongly positive reagent strip and a negative Clinitest, however, should cause concern about possible contamination by strong oxidizing agents. The most significant discrepancy is the
negative reagent strip with a positive Clinitest. Although interfering substances affecting either test may cause this problem, the most frequent cause is the presence of other reducing sugars in the urine. Commonly found reducing sugars include galactose, fructose, pentose, and lactose, of which galactose is the most clinically significant.
Other than glucose, name another clinically significant reducing sugar
galactose (inborn error of metabolism)
Glycosuria during a cerebrovascular trauma may be caused by:
epinephrine inhibiting insulin and producing glycogenolysis
Epinephrine is a strong inhibitor of insulin secretion and is increased when the body is subjected to severe stress, which accounts for the glucosuria seen in conjunction with cerebrovascular trauma
and myocardial infarction.
A primary function of insulin is to convert
glucose to glycogen for storage (glycogenesis), these opposing hormones cause the breakdown of glycogen to glucose (glycogenolysis), resulting in increased levels of circulating glucose.
Glucosuria (sugar in urine) not in conjunction with hyperglycemia (excess blood glucose) is a symptom of:
Explain the steps to a glucose oxidase reaction:
Reagent strips employ the glucose oxidase testing method by impregnating the testing area with a mixture of glucose oxidase, peroxidase, chromogen, and buffer to produce a double sequential enzyme
Step 1: glucose oxidase catalyzes a reaction between glucose and room
air to produce gluconic acid and peroxide.
Step 2: peroxidase catalyzes the
reaction between peroxide and chromogen to form an oxidized colored compound that
represents the presence of glucose.
Galactose will react on the _____ test
(Chemstrip and multistix are specific for glucose. Both of these tests use a glucose oxidase reaction. Clinitest uses the copper reduction method)
Explain the phenomenon known as "pass through" that can happen with Clinitest
When conducting a Clinitest, care must be taken to observe the reaction closely as it is taking place, because at high glucose levels, a phenomenon known as "pass through" may occur. When this happens, the color produced passes through the orange/red stage and returns to a green-brown color, and if not observed, a high glucose level may be reported as negative.
A trace reaction on a reagent strip and a high Clinitest reaction is observed. What could cause this to happen?
In this case, these two reactions would indicate the presence of glucose and other reducing substances.
However, there are several explanations for the finding of conflicting results between the two glucose tests. The Clinitest is not as sensitive as the glucose oxidase test, so the finding of a 1+ reagent strip reading and a negative Clinitest should not be surprising. A strongly positive reagent strip and a negative Clinitest, however, should cause concern about possible contamination by strong oxidizing agents.
The most significant discrepancy is the negative reagent strip with a positive Clinitest. Although interfering substances affecting either test may cause this problem, the most frequent cause is the presence of other reducing sugars in the urine. As a nonspecific test for reducing substances, Clinitest is subject to interference from other reducing sugars, including galactose, lactose, fructose, maltose, pentoses, ascorbic acid, certain drug metabolites, and antibiotics such as the cephalosporins. Therefore, Clinitest does not provide a confirmatory test for glucose.
If you have a negative reagent strip reaction with a positive Clinitest, what might this indicate?
The most significant discrepancy between these two tests is the negative reagent strip with a positive Clinitest. Although interfering substances affecting either test may cause this discrepancy, the most frequent cause is the presence of other reducing sugars in the urine with the detection of galactose being the most clinically significant. Galactose in the urine of a newborn represents an "inborn error of metabolism" in which lack of the enzyme galactose-1-phosphate uridyl transferase prevents breakdown of ingested galactose and results in failure to thrive and other complications, including death. All newborns should be screened for galactosuria because early detection followed by dietary restriction control the condition.
The term ketones represents three intermediate products of fat metabolism. Name them.
2. acetoacetic acid
3. beta-hydroxybutyric acid
Why would you find the presence of ketones in the urine?
Normally, measurable amounts of ketones do not appear in the urine, because all the metabolized fat is completely broken down into carbon dioxide and water. However, when the use of available carbohydrate as the major source of energy becomes compromised, body stores of fat must be metabolized to supply energy. Ketones are then detected in urine.
What are some clinical reasons for increased fat metabolism? (Remember that the presense of ketones signifies increased fat metabolosim)
1. Inability to metabolize carbohydrate, as occurs in diabetes mellitus;
2 Increased loss of carbohydrate from vomiting;
3. Iinadequate intake of carbohydrate associated with starvation
Reagent strip tests use the sodium nitroprusside reaction to measure ketones. What substance(s) does the reagent strip react with to detect the presence of ketones?
In this reaction, acetoacetic acid in an alkaline medium reacts with sodium nitroprusside to produce a purple color.
The test does not measure beta-hydroxybutyric acid and is only slightly sensitive to acetone when glycine is also present;
In a reagent test for ketones, what is being detected?
The presence of acetoacetic acid and acetone (It will only detect the presence of acetone if glycine s present)
In a reagent strip test for keytones, what are th names of the reagents?
sodium nitroprusside and glycine
Chemical tests for _____ provide the most accurate means for determining the presence of blood
Because any amount of blood greater than five cells per microliter of urine is considered clinically significant, visual examination cannot be relied upon to detect the presence of blood. Microscopic examination of the urinary sediment shows intact red blood cells, but free
hemoglobin produced either by hemolytic disorders or lysis of red blood cells is not detected.
Once blood has been detected, the _____ can be used to differentiate between hematuria and hemoglobinuria.
Chemical tests for blood use the _____ to catalyze a
reaction between hydrogen peroxide and the chromogen tetramethylbenzidine to produce an oxidized chromogen, which has a green-blue color.
pseudoperoxidase acptivity of hemoglobin
Myoglobinuria may be caused by:
1 extensive overexertion (strenuous exercise)
2 Muscle trauma (crush syndrome)
3. Alcoholism/drug abuse
In hemoglobinuria, lysis of the red blood cells in the urine shows up as ____
a mixture of hemoglobin and hematuria
In ______ a reagent stip will test positive for blood, however, red blood cells will not be seen on a microscopic examination.
The diagnosis of _____ is usually based on elevated serum levels of the enzymes creatinine kinase and lactic dehydrogenase. The appearance of the patient's plasma can also aid in the differentiation.
The kidneys rapidly clear myoglobin from the plasma, leaving a normal appearing plasma,
________ bound to haptoglobin remains in the plasma and
imparts a red color.
Hemoglobin bound to haptoglobin remains in the plasma and imparts a red color.
Bilirubin combines with _____ in an acid medium to produce a colored azodye
diazonium salt / colored azo-dye
Hemoglobin is broken down becoming bilirubin where it is released into the circulation as ______. It then binds with ______ and in the liver and becomes "conjugated bilirubin"
unconjugated bilirubin/ albumin
_____ does not appear in the urine because it is passed directly from the liver into the bile duct and on to the intestine.
______appears in the urine when the normal degradation cycle is disrupted by obstruction of the bile duct or when the integrity of the liver is damaged, allowing leakage of ______ into the circulation.
conjugated bilirubin/ Conjugated bilirubin
_____ and _____ may lower the sensitivity of the test for bilirubin because they combine with the diazonium salt and prevent its reaction with bilirubin.
High concentrations of ascorbic acid and nitrite
What is the most frequent error that causes a false-negative results in biliruben testing
testing using old specimens
Bilirubin is an unstable compound that is rapidly photo-oxidized to ______ when exposed to light
Name some reason to get a false negative with the test for biliruben:
1. Light exposure
2. ascorbic acid
Questionable results for bilirubin testing with reagent strips can be repeated using the ____
The _____ is less subject to interference and is more sensitive to bilirubin than ____
Because of its higher sensitivity, an _____ may be requested to detect early stages of liver disease.
With a bile duct obstruction, what will the strip show for bilirubin? urobilinogen?
Bile Duct Obstruction
With liver disease, what will the strip show for bilirubin? urobilinogen?
+ or - ++
Intestinal bacteria reduce bilirubin to ______ which is then oxidized and excreted in the feces in the form of urobilin
What is the clinical Significance of Urine Urobilinogen?
1. Early detection of liver disease
2. Hemolytic disorders
Although it cannot be determined by reagent strip, the absence of ______ in the urine and feces is also diagnostically significant and represents an obstruction of the bile duct that prevents the normal passage of bilirubin into the intestine.
_____cannot determine the absence of
urobilinogen, which is significant in biliary obstruction
Reagent strip tests
The reagent strip test for nitrite provides a rapid screening test for the presence of ______
urinary tract infection
The chemical basis of the nitrite test is the ability of certain bacteria _______ which does not normally appear in the urine.
to reduce nitrate, a normal constituent of urine, to nitrite,
Nitrite is detected by the _____, in which nitrite at an acidic pH reacts with sulfanilamide to form a diazonium compound that produces a ______
Greiss reaction / pink-colored azodye.
What can produce a false negative nitrite test:
1. non-reductase containing bacteria
2. Insufficient contact time between bacteria and urinary nitrate
3. ascorbic acid
4. high specific gravity
The leukocyte esterase reagent strip will detect the presence of :
neutrophils, eosinophils, basophils and monocytes.
A positive LE test result is most frequently accompanied by the presence of bacteria, which may or may not produce a positive nitrite reaction. Infections caused by Trichomonas, Chlamydia, yeast, and inflammation of renal tissues produce ______ without ______
leukocyturia without bacteriuria.
How does the reagent test (LE test) work?
The LE (leukocyte esterase) test detects the presence of esterase in the granulocytic white blood cells (neutrophils,eosinophils, and basophils) and monocytes. Esterases also are present in Trichomonas and histiocytes.
How are the quantities of leukocytes measured?
The LE reagent test is not designed to measure the concentration of leukocytes, and the manufacturers recommend that quantitation be done by microscopic examination.
Most common false negative reaction for the LE reagent test is:
Not waiting a full 2 minutes before reading
What is the Clinical Significance of Urine Specific Gravity
1. Monitoring patient hydration and dehydration
2. Loss of renal tubular concentrating ability
3. Diabetes insipidus
4. Determination of unsatisfactory specimens due to low concentration
How does the reagent strip for specific gravity work?
A polyelectrolyte ionizes, and releases hydrogen ions in
proportion to the number of ions in the solution. The higher the concentration of urine, the more hydrogen ions are released, thereby lowering the pH. This change is measured by bromthymol blue on the reagent pad
As the specific gravity increases (using reagent strip) the indicator changes from ______ to _______ to ______
blue to green to yellow
As the specific gravity increases, the indicator changes from blue (1.000 [alkaline]), through shades of green, to
yellow (1.030 [acid]). Readings can be made in 0.005 intervals by careful comparison with the color chart.
Failure to blot the reagent strip will cause runover of reagents on the pads. This will affect ____ the most
Ascorbic acid will negatively affect the results of which tests on the reagent strip?