Achievable logoAchievable logo
CCMA
Sign in
Sign up
Purchase
Textbook
Practice exams
Support
How it works
Resources
Exam catalog
Mountain with a flag at the peak
Textbook
Introduction
1. Medical assistant
2. Electronic records
3. Medical terminology and anatomy
4. The fundamentals of infection control
5. Introduction to vital signs
6. The patient interview and history
7. The physical examination
8. Appointment scheduling
9. Insurance billing
10. Diagnostic coding and the ICD-10-CM System
11. Procedural coding
12. Medical billing and reimbursement essentials
13. Assisting with medical specialties
14. Assisting with the musculoskeletal system
15. Assisting with the cardiovascular system
16. Assisting with the respiratory system
17. Assisting with the nervous system
18. Anatomy and physiology of the urinary system
19. Assisting in obstetrics and gynecology
20. Assisting in endocrinology
21. Assisting in ophthalmology & otolaryngology
22. Assisting in gastroenterology
23. Assisting in the immune & lymphatic systems
24. Assisting in pediatrics: the developmental stages and care
25. The medical assistant’s role in caring for the older patient
26. The role of the medical assistant in physical therapy examination and assessment
27. Preparing for minor surgery: room, solutions, and supplies
28. Introduction to the clinical laboratory
29. Urinalysis
29.1 Urine formation and specimen collection
29.2 Urine specimen collection methods and handling
29.3 Physical examination of urine
29.4 Chemical examination of urine
29.5 Quality control in urinalysis
29.6 Additional CLIA-waived urine tests
29.7 Microscopic preparation of urine and cellular findings
29.8 Urine crystals, miscellaneous findings, and reporting results
29.9 Urine toxicology, legal issues, and professional practice
30. Blood collection
31. Analysis of blood
32. Electrocardiography and heart structure
33. The principles of pharmacology
34. Essential calculations and measurement systems
35. Solid, liquid, & solutions medication doses
36. Administering medications
37. Metabolism and core nutrient roles
38. Medical emergencies in the healthcare setting
Achievable logoAchievable logo
29.5 Quality control in urinalysis
Achievable CCMA
29. Urinalysis

Quality control in urinalysis

7 min read
Font
Discuss
Share
Feedback

Blood

The presence of blood in urine may indicate infection or trauma to the urinary tract. The blood test pad on the reagent strip reacts with three different blood constituents: intact (whole) red blood cells, hemoglobin from lysed (broken) red blood cells, and myoglobin.

Hematuria is the presence of intact red blood cells in urine. The color reaction on the reagent strip ranges from yellow to green to dark green when hematuria is present, revealing a speckled appearance. Hematuria can be caused by irritation of the kidneys, ureters, bladder, or urethra. It also is a common finding in cystitis (inflammation of the urinary bladder) and in individuals passing kidney stones. A random specimen may contain blood from vaginal contamination if the woman is menstruating.

Hemoglobinuria is the presence of hemolyzed (ruptured, broken) red blood cells in urine. True hemoglobinuria is not common. But urine specimens that contain blood may test positive for hemolyzed blood for a few reasons:

  • The urine specimen has sat for too long at room temperature, causing the RBCs to lyse. Freshly collected specimens give the most accurate testing results.
  • The pH of the urine is highly alkaline, which can cause RBCs to lyse.
  • The specific gravity of the sample is below 1.010; this can also cause RBCs to lyse.
  • Bacteria in the urine can also cause a false-positive hemolyzed blood test result.

Finding blood or hemolyzed blood on the urine dipstick should be confirmed by microscopic examination of the urine. If intact RBCs are seen microscopically, this should be noted on the UA report to the provider. (A medical assistant would not be doing the microscopic exam.) True hemoglobinuria is the result of intravascular red blood cell destruction and can be caused by blood transfusion reactions, malaria, drug reactions, snakebites, and severe burns.

Myoglobinuria (myoglobin in the urine) occurs when muscle tissue is damaged or injured. This can occur with crushing injuries, myocardial infarctions, contact sports, or strenuous exercise. Patients with muscular dystrophy often have myoglobinuria. Hemoglobinuria cannot be distinguished from myoglobinuria by reagent strip testing. Both cause a uniform change in color from light green to dark green on the strip. Myoglobin testing is not normally part of the urine dipstick.

Bilirubin and urobilinogen

Bilirubin is a product of the breakdown of hemoglobin. Hemoglobin is released from old red blood cells and is gradually converted to bilirubin in the liver. The liver excretes this bilirubin in bile into the intestines, where intestinal bacteria convert it to urobilinogen; some urobilinogen is reabsorbed and returned to the liver, and a small amount is excreted in the urine. Bilirubin is a bile pigment not normally found in urine. Its presence in urine is one of the first signs of liver disease or other diseases in which the liver may be involved.

Bilirubin in the urine (bilirubinuria) can occur even before jaundice or other symptoms of liver disease are evident. It is the result of liver cell damage or obstruction of the common bile duct by stones or tumors. Excessive bilirubin colors the urine yellow-brown to greenish orange. Because direct light causes bilirubin to break down, urine samples must be protected from light until testing is complete.

Urobilinogen normally is present in urine in small amounts. Elevated urobilinogen is seen with increased red blood cell destruction, liver disease, or total obstruction of the bile duct.

Nitrite

Nitrate is a common component of normal urine. Nitrites occur in urine when bacteria break down nitrate. A positive nitrite test result may indicate the presence of a UTI. However, not all bacteria are able to break down nitrate to nitrite. A negative nitrite test can occur when bacteria are in small numbers or when the urine has not been in the bladder long enough for the chemical breakdown to occur. Escherichia coli (E. coli), the bacteria that is the most common cause of UTIs, does break down nitrate to nitrite. A positive reaction is any pink color on the nitrite dipstick pad.

Leukocyte esterase

Leukocytes (white blood cells) are present in the urine when a person has a UTI. The leukocyte esterase test pad on the reagent strip takes 2 minutes to release esterase from white blood cells. Wait a full 2 minutes before reading the leukocyte esterase result. The test does not react with small numbers of white blood cells found in normal urine. A false-positive result could be caused by WBC contaminants from the vagina, especially if the sample is allowed to sit at room temperature. Urine specimens should be tested as soon as possible after collection. If this is not possible, the specimen should be refrigerated.

Limitations of reagent strip testing

The reagent strip is a reliable method of testing urine if used properly. Errors can arise from several sources:

  • The test strip is soaked in the specimen, and chemicals in the pads may be overly diluted.
  • The test strip is not held horizontally while read, and colors from one pad may bleed onto another.
  • The test pads on the strip are not read at the proper time, or the chemical reaction may be read incorrectly.
  • Certain chemicals, such as vitamin C, also called ascorbic acid, may affect the results of nitrite, glucose, bilirubin, and blood tests. Normal levels of vitamin C do not interfere with routine urinalysis, but large amounts can alter test results. Be sure to check the package insert for a list of all interfering substances.

Visual interpretation of reagent strip colors is likely to vary among individuals, so some laboratories use automated instruments that read the strip’s color changes and print out digital results. The advantage is consistent timing and color interpretation, but the disadvantage is that the instrument can’t adjust for highly colored urine, so darkly colored specimens should be tested manually or sent to a reference lab.

Quality assurance and quality control in urinalysis

Once you know how to interpret each analyte on the strip, the next step is making sure the testing process itself produces reliable results.

The US Food and Drug Administration (FDA) categorizes the chemical analysis of urine performed by an instrument or a reagent strip as a CLIA-waived test. The chemical analysis includes the reagent strip (dipstick) tests for bilirubin, glucose, hemoglobin or blood, ketones, leukocyte esterase, nitrite, pH, protein, specific gravity, and urobilinogen. A commercially available control strip should be used to determine the reliability of the reagent strips used in chemical analysis. One such control strip is the Chek-Stix, which is available in positive (abnormal) and negative (normal) versions. Record the results produced by both controls, and confirm they’re consistent with the manufacturer’s Chek-Stix charts before testing patient urine specimens.

Normal urine reference ranges for reagent strips

Property Reference range
Color Pale yellow to amber
Clarity Clear to slightly turbid
Specific gravity 1.005-1.030
pH 5.5-8
Protein (mg/dL) NEG
Glucose (mg/dL) NEG
Ketone (mg/dL) NEG
Bilirubin (mg/dL) NEG
Blood (mg/dL) NEG
Nitrite (mg/dL) NEG
Urobilinogen (Ehrlich units) 0.1-1
White blood cells NEG

The Chek-Stix is one type of commercial control, but other strips and prepared liquid controls are also available. Each POL should investigate the best commercial control for its needs and quality control program.

Sign up for free to take 17 quiz questions on this topic

Previous
Next  | 29.6 Additional CLIA-waived urine tests
All rights reserved ©2016 - 2026 Achievable, Inc.

Quality control in urinalysis

Blood

The presence of blood in urine may indicate infection or trauma to the urinary tract. The blood test pad on the reagent strip reacts with three different blood constituents: intact (whole) red blood cells, hemoglobin from lysed (broken) red blood cells, and myoglobin.

Hematuria is the presence of intact red blood cells in urine. The color reaction on the reagent strip ranges from yellow to green to dark green when hematuria is present, revealing a speckled appearance. Hematuria can be caused by irritation of the kidneys, ureters, bladder, or urethra. It also is a common finding in cystitis (inflammation of the urinary bladder) and in individuals passing kidney stones. A random specimen may contain blood from vaginal contamination if the woman is menstruating.

Hemoglobinuria is the presence of hemolyzed (ruptured, broken) red blood cells in urine. True hemoglobinuria is not common. But urine specimens that contain blood may test positive for hemolyzed blood for a few reasons:

  • The urine specimen has sat for too long at room temperature, causing the RBCs to lyse. Freshly collected specimens give the most accurate testing results.
  • The pH of the urine is highly alkaline, which can cause RBCs to lyse.
  • The specific gravity of the sample is below 1.010; this can also cause RBCs to lyse.
  • Bacteria in the urine can also cause a false-positive hemolyzed blood test result.

Finding blood or hemolyzed blood on the urine dipstick should be confirmed by microscopic examination of the urine. If intact RBCs are seen microscopically, this should be noted on the UA report to the provider. (A medical assistant would not be doing the microscopic exam.) True hemoglobinuria is the result of intravascular red blood cell destruction and can be caused by blood transfusion reactions, malaria, drug reactions, snakebites, and severe burns.

Myoglobinuria (myoglobin in the urine) occurs when muscle tissue is damaged or injured. This can occur with crushing injuries, myocardial infarctions, contact sports, or strenuous exercise. Patients with muscular dystrophy often have myoglobinuria. Hemoglobinuria cannot be distinguished from myoglobinuria by reagent strip testing. Both cause a uniform change in color from light green to dark green on the strip. Myoglobin testing is not normally part of the urine dipstick.

Bilirubin and urobilinogen

Bilirubin is a product of the breakdown of hemoglobin. Hemoglobin is released from old red blood cells and is gradually converted to bilirubin in the liver. The liver excretes this bilirubin in bile into the intestines, where intestinal bacteria convert it to urobilinogen; some urobilinogen is reabsorbed and returned to the liver, and a small amount is excreted in the urine. Bilirubin is a bile pigment not normally found in urine. Its presence in urine is one of the first signs of liver disease or other diseases in which the liver may be involved.

Bilirubin in the urine (bilirubinuria) can occur even before jaundice or other symptoms of liver disease are evident. It is the result of liver cell damage or obstruction of the common bile duct by stones or tumors. Excessive bilirubin colors the urine yellow-brown to greenish orange. Because direct light causes bilirubin to break down, urine samples must be protected from light until testing is complete.

Urobilinogen normally is present in urine in small amounts. Elevated urobilinogen is seen with increased red blood cell destruction, liver disease, or total obstruction of the bile duct.

Nitrite

Nitrate is a common component of normal urine. Nitrites occur in urine when bacteria break down nitrate. A positive nitrite test result may indicate the presence of a UTI. However, not all bacteria are able to break down nitrate to nitrite. A negative nitrite test can occur when bacteria are in small numbers or when the urine has not been in the bladder long enough for the chemical breakdown to occur. Escherichia coli (E. coli), the bacteria that is the most common cause of UTIs, does break down nitrate to nitrite. A positive reaction is any pink color on the nitrite dipstick pad.

Leukocyte esterase

Leukocytes (white blood cells) are present in the urine when a person has a UTI. The leukocyte esterase test pad on the reagent strip takes 2 minutes to release esterase from white blood cells. Wait a full 2 minutes before reading the leukocyte esterase result. The test does not react with small numbers of white blood cells found in normal urine. A false-positive result could be caused by WBC contaminants from the vagina, especially if the sample is allowed to sit at room temperature. Urine specimens should be tested as soon as possible after collection. If this is not possible, the specimen should be refrigerated.

Limitations of reagent strip testing

The reagent strip is a reliable method of testing urine if used properly. Errors can arise from several sources:

  • The test strip is soaked in the specimen, and chemicals in the pads may be overly diluted.
  • The test strip is not held horizontally while read, and colors from one pad may bleed onto another.
  • The test pads on the strip are not read at the proper time, or the chemical reaction may be read incorrectly.
  • Certain chemicals, such as vitamin C, also called ascorbic acid, may affect the results of nitrite, glucose, bilirubin, and blood tests. Normal levels of vitamin C do not interfere with routine urinalysis, but large amounts can alter test results. Be sure to check the package insert for a list of all interfering substances.

Visual interpretation of reagent strip colors is likely to vary among individuals, so some laboratories use automated instruments that read the strip’s color changes and print out digital results. The advantage is consistent timing and color interpretation, but the disadvantage is that the instrument can’t adjust for highly colored urine, so darkly colored specimens should be tested manually or sent to a reference lab.

Quality assurance and quality control in urinalysis

Once you know how to interpret each analyte on the strip, the next step is making sure the testing process itself produces reliable results.

The US Food and Drug Administration (FDA) categorizes the chemical analysis of urine performed by an instrument or a reagent strip as a CLIA-waived test. The chemical analysis includes the reagent strip (dipstick) tests for bilirubin, glucose, hemoglobin or blood, ketones, leukocyte esterase, nitrite, pH, protein, specific gravity, and urobilinogen. A commercially available control strip should be used to determine the reliability of the reagent strips used in chemical analysis. One such control strip is the Chek-Stix, which is available in positive (abnormal) and negative (normal) versions. Record the results produced by both controls, and confirm they’re consistent with the manufacturer’s Chek-Stix charts before testing patient urine specimens.

Normal urine reference ranges for reagent strips

Property Reference range
Color Pale yellow to amber
Clarity Clear to slightly turbid
Specific gravity 1.005-1.030
pH 5.5-8
Protein (mg/dL) NEG
Glucose (mg/dL) NEG
Ketone (mg/dL) NEG
Bilirubin (mg/dL) NEG
Blood (mg/dL) NEG
Nitrite (mg/dL) NEG
Urobilinogen (Ehrlich units) 0.1-1
White blood cells NEG

The Chek-Stix is one type of commercial control, but other strips and prepared liquid controls are also available. Each POL should investigate the best commercial control for its needs and quality control program.

More from Urinalysis

  • Urine formation and specimen collection
  • Urine specimen collection methods and handling
  • Physical examination of urine
  • Chemical examination of urine
  • Additional CLIA-waived urine tests