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Urobilinogen Information and Courses from MediaLab, Inc.

These are the MediaLab courses that cover Urobilinogen and links to relevant pages within the course.

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Chemical Screening of Urine by Reagent Strip
Chemical Urinalysis Reagent Strips

A chemical urinaylsis reagent strip, also called a dipstick, for screening urine is a narrow band of paper which has been saturated with chemical indicators for specific substances or properties. Depending on the product being used, chemical urinalysis reagent strips may include test indicators for glucose, bilirubin, ketones, specific gravity, blood, pH, protein, urobilinogen, nitrite, and leukocyte esterase. The results obtained from urine screening using chemical urinalysis strips can indicate the patient's carbohydrate metabolism status, kidney and liver function, urinary tract infection, and acid-base balance. Most chemical urinalysis reagent strips can be read visually and do not require instrumentation for automatic reading, though many laboratories utilize instruments for this purpose. When performing chemical urinalysis reagent strip analysis, the directions must be performed exactly. Accurate timing is paramount in order to achieve appropriate and optimal results. In addition, the reagent strips must be stored properly in their containers with the lid tightly closed to maintain reagent reactivity. It is always essential to utilize well-mixed urine which has been collected within 2 hours of analysis.Always read the package insert for your particular brand of chemical urinalysis reagent strip, as each manufacturer may have slightly different instructions and interpretations.

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Overview of Bilirubin

Bilirubin, a product of hemoglobin catabolism, is characterized by its distinctive yellow pigment. The presence of bilirubin in urine is always abnormal. In most healthy individuals the amount of conjugated bilirubin excreted is not detected by the strips. In cases when bilirubin is elevated and is conjugated, it will be detected by the test strip.It is important to note that unconjugated bilirubin cannot be excreted by the kidneys because it is bound to albumin and is not soluble in water. In the liver, bilirubin combines with glucuronic acid through the action of a glucuronyl transferase to form water soluble bilirubin diglucuronide. Under normal circumstances, conjugated bilirubin passes from the bile duct and then to the intestinal tract. Intestinal bacteria reduce conjugated bilirubin to urobilinogen. Approximately half of the urobilinogen is excreted in the feces; most of the other half is recirculated through the liver. A small amount of urobilinogen bypasses the liver and is excreted in the urine.

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Which of the following may cause a false positive bilirubin result on a urine chemical reagent strip?View Page
Introduction to Urobilinogen

Urobilinogen is a byproduct of hemoglobin breakdown. It is produced in the intestinal tract as a result of the action of bacteria on bilirubin. Almost half of the urobilinogen produced recirculates through the liver and then returns to the intestines through the bile duct. Urobilinogen is then excreted in the feces where it is converted to urobilin. As the urobilinogen circulates in the blood to the liver, a portion of it is diverted to the kidneys and appears as urinary urobilinogen. Up to 1 mg/dL or Ehrlich unit of urobilinogen is present in normal urine. A result of 2.0 mg/dL represents the transition from normal to abnormal levels of urobilinogen and the patient should be evaluated further. It is important to note that the chemical reagent strip cannot determine the absence of urobilinogen, so a negative result is impossible.

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Urobilinogen Analysis

The test for urobilinogen is based on the Ehrlich Aldehyde Reaction. P-dimethylaminobenzaldehyde in an acid medium with a color enhancer reacts with urobilinogen to form a pink-red color. The urine chemical reagent strip reactivity increases with increasing temperature. The optimum temperature for testing is 22° - 26°C. A freshly voided sample is always best for ensuring optimal results.

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False-Positive and False-Negative Urobilinogen Results

False-positive results:A false positive urobilinogen reaction may occur with the chemical reagent strip method when substances known to react with Ehrlich's reagent such as sulfonamides and p-aminosalicylic acid are present in the urine. Drugs that contain Azo dyes, such as Azo Gantrisin®, have a gold color that masks the reaction, causing a false positive reaction. Atypical color reactions may be obtained in the presence of high concentrations of p-aminobenzoic acid. The chemical reagent strip urobilinogen test cannot detect porphobilinogen in a urine specimen. Porphobilinogen is a molecule formed during the synthesis of the heme portion of hemoglobin. False-negative resultsDue to the instability of urobilinogen, a false negative result may occur using the chemical reagent strip method if the urine specimen has remained at room temperature for an extended period of time exposed to light. A false negative result may also occur if formalin is present.

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Confirmatory Testing for Urobilinogen

Test results that are 2.0 Ehrlich units or greater can be confirmed using the Watson-Schwartz qualitative test. This test will differentiate between urobilinogen and porphobilinogen.

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Clinical Significance of Urobilinogen in Urine

Urinary urobilinogen may be increased in the presence of a hemolytic process such as hemolytic anemia. It may also be increased with infectious hepatitis, or with cirrhosis. Comparing the urinary bilirubin result with the urobilinogen result may assist in distinguishing between red cell hemolysis, hepatic disease, and biliary obstruction, as shown in the table below:ConditionUrine Bilirubin ResultUrine Urobilinogen ResultHemolytic diseaseNegativeIncreasedHepatitic diseasePositive or negativeIncreasedBiliary obstructionPositiveNormal* *Urine chemical reagent strip methods cannot distinguish normal urobilinogen from absent urobilinogen, as might be seen in complete biliary obstruction.

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A test that can be used as a confirmatory test for urobilinogen is:View Page
In hemolytic disease, the urine bilirubin test result is negative and the urine urobilinogen test result is:View Page
To screen for urinary tract infections, leukocyte esterase results should be evaluated along with the results from which of these other reagent strip tests?View Page

Chemical Screening of Urine by Reagent Strip (retired March 2012)
Which of the following tests included on a urine reagent strip would never be reported out as negative?View Page
Excessive carbohydrate loss that may occur due to vomiting, or rapid weight loss may result in the presence of which of following substances not normally contained in the urine?View Page
Which of the following reagent strip tests is based on the Ehrlich- aldehyde reaction.View Page
Sulfosalicylic acid can be used to confirm the result of which of the following tests included on a urine reagent strip?View Page
Bilirubin Characterization

Bilirubin, a product of hemoglobin breakdown, is characterized by its yellow pigment. The presence of bilirubin in urine is always abnormal. It is important to note that unconjugated bilirubin cannot be excreted by the kidneys because it is bound to albumin and is not soluble in water. In the liver, bilirubin combines with glucuronic acid through the action of a glucuronyl transferase to form water soluble bilirubin diglucuronide. Under normal circumstances, conjugated bilirubin passes from the bile duct and then to the intestinal tract. Intestinal bacteria reduce conjugated bilirubin to urobilinogen. Approximately half of the urobilinogen is excreted in the feces; most of the other half is recirculated through the liver. A small amount of urobilinogen bypasses the liver and is excreted in the urine.

View Page
Which of the following may cause a false positive bilirubin result on a urine reagent strip?View Page
Which of the following may cause false negative bilirubin results on a urine reagent strip? (Choose ALL of the correct answers)View Page
Urobilinogen

Urobilinogen is a byproduct of hemoglobin breakdown. It is produced in the intestinal tract as a result of the action of bacteria on bilirubin. Almost half of the urobilinogen produced recirculates through the liver and then returns to the intestines through the bile duct. Urobilinogen is then excreted in the feces where it is converted to urobilin. As the urobilinogen circulates in the blood to the liver, a portion of it is diverted to the kidneys and appears as urinary urobilinogen. Up to 1 mg/dL or Ehrlich unit of urobilinogen is present in normal urine. A result of 2.0 mg/dL represents the transition from normal to abnormal and the patient should be evaluated further. It is important to note that the reagent strip cannot determine the absence of urobilinogen.

View Page
The Test for Urobilinogen

The test for urobilnogen is based on the Ehrlich Aldehyde Reaction. P-dimethylaminobenzaldehyde in an acid medium with a color enhancer reacts with urobilinogen to form a pink-red color. The strip reactivity increases with increasing temperature. The optimum temperature for testing is 22° - 26°C. A freshly voided sample is best for optimal results.

View Page
False Positive Urobilinogen Results

A false positive urobilinogen reaction may occur with the dipstick method when substances known to react with Ehrlich's reagent such as sulfonamides and p-aminosalicylic acid are present in the urine. Drugs that contain Azo dyes, such as Azo Gantrisin®, have a gold color that masks the reaction, causing a false positive reaction. Atypical color reactions may be obtained in the presence of high concentrations of p-aminobenzoic acid. The dipstick urobilinogen test cannot detect porphobilinogen in a urine specimen. Porphobilinogen is a molecule formed during the synthesis of the heme portion of hemoglobin.

View Page
False Negative Urobilinogen Result

Due to the instability of urobilinogen, a false negative result may occur using a dipstick method if the urine specimen has remained at room temperature for an extended period of time in the light. A false negative result may also occur if formalin is present.

View Page
Confirmatory Test

Test results that are 2.0 Ehrlich units or greater can be confirmed using the Watson-Schwartz qualitative test. This test will differentiate between urobilinogen and porphobilinogen.

View Page
Clinical Significance

Urinary urobilinogen may be increased in the presence of a hemolytic process such as hemolytic anemia. It may also be increased with infectious hepatitis, or with cirrhosis. Comparing the urinary bilirubin result with the urobilinogen result may assist in distinguishing between red cell hemolysis, hepatic disease, and biliary obstruction. Urobilinogen is increased in hemolytic disease and urine bilirubin is negative. Urobilinogen is increased in hepatic disease, and urine bilirubin may be positive or negative. Urobilinogen is low with biliary obstruction, and urine bilirubin is positive. Reagent strips methods however, cannot distinguish normal urobilinogen from absent urobilinogen, as might be seen in complete biliary obstruction.

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Which of the following substances cause a false-positive reaction on the urobilinogen portion of the test strip? (Choose ALL of the correct answers)View Page
Which of the following cause false negative reactions when testing for urobilinogen with the reagent strips? (Choose ALL of the correct answers)View Page
A test that can be used as a confirmatory test for urobilinogen is:View Page
Urobilinogen is excreted in the urine in increased amounts in: (Choose ALL of the correct answers)View Page
To screen for urinary tract infections leukocyte esterase should be coupled with: (Choose ALL of the correct answers)View Page

Confirmatory and Secondary Urinalysis Screening Tests
A urine specimen is received in the laboratory late in the afternoon. The specimen was collected early in the morning and was accidentally left in bright sunlight and at room temperature on a counter in the outpatient clinic. The test order is for urine bilirubin screening. Which of the following could occur as a result of the storage conditions?View Page


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