CHEMSTRIP 10SG CHEMICAL ANALYSIS OF URINE
PRINCIPLE
The chemical analysis of urine is a vital part of the routine urinalysis. The Chemstrip 10SG urine test strips are inert plastic strips to which are attached different chemically impregnated test sites on an absorbent pad for determining specific gravity, pH, leukocytes, nitrite, protein, glucose, ketones, urobilinogen, bilirubin, and blood/hemoglobin in urine. Refer to the package insert for the specific test principles and parameters. When the dry reagents come in contact with urine or a suitable control solution, the reagents are activated and a chemical reaction occurs. The chemical reaction is a specific color change. This is observed visually and compared with a special color chart provided by the manufacturer. The intensity of the color formed is generally proportional to the amount of substance present in the specimen at a specific time. Some tests are used as screening tests (presence or absence) while others are used to estimate (semiquantitate) the amount of substance present and reported in a plus system or in numerical values.
SPECIMEN
Fresh, uncentrifuged, well mixed urine or QC solutions at room temperature.
1. Patient Preparation—N/A
2. Type
Random specimens
First morning void – most concentrated
Timed specimens (such as complete 24-hour collections
Double-voided specimens
Midstream-voided specimens (used for routine urinalysis)
Clean-catch midstream – specimen of choice
Catheterized urine – performed when the patient has dysuria or is incontinent.
The patient should receive oral and detailed written instructions for the desired urine collection technique. See urine specimen collection procedure.
3. Handling Conditions—Specimens should be tested within one hour of collection or immediately refrigerated at 2-8oC.
4. Rejection criteria for samples
Specimens without acceptable labels.
Discrepant information on labels and requisitions.
Insufficient quantity for test requested (1mL or less)
Grossly contaminated (i.e. foreign materials, fecal matter) are to be rejected for testing.
EQUIPMENT AND MATERIALS
1. Equipment
Timer
2. Materials
Chemstrip 10SG dipsticks
3. Preparation—If this is the first specimen of the day, perform QUALITY CONTROL.
4. Performance Parameters—N/A
5. Storage Requirements
· The Chemstrip 10SG dipsticks must be kept in tightly capped or stoppered containers. Strips will deteriorate when exposed to moisture, direct sunlight, heat, or volatile substances.
· Do not remove the desiccant from the container. Store at room temperature.
· Remove only the number of strips needed at a time, and keep the container tightly closed at all times. Do not touch test areas.
CALIBRATION – N/A
QUALITY CONTROL
Quality control testing with 2 levels of liquid control material (Bio Rad Liquichek level 1 & 2 Controls) should be conducted prior to daily testing. Distilled water may be used as a negative control. The control system is used to determine accuracy and precision in the measurement of the physical and chemical tests commonly employed in semiquantitative urine testing. Quality control results must be recorded and available for reference.
1. If the product has been refrigerated, warm one vial of each level of control to room temperature, 18o-30oC (15-30 minutes). Verify that the lot number indicated on each control bottle matches the assay sheet enclosed.
2. Remove the dropper tip cap. Holding the dipstick reagent strip in one hand, invert the control bottle and apply control material directly across each pad by gently squeezing the bottle.
3. Remove excess control by tilting the dipstick on its edge and blotting on an absorbent towel.
4. If reading the results visually, follow the manufacturer’s instructions completely, comparing the color reactions at the designated times to the appropriate strip area.
5. Wipe the tip of the control bottle and recap.
6. Control stability—The Bio Rad control is stable after opening for 31 days at room temperature. When refrigerated, the product is stable until it’s expiration date. Freeze aliquots of each control before the expiration date for use after the material has expired.
7. Record the reaction of each test on the appropriate quality control chart.
Proficiency Testing: Successful participation in the USDOS PT Program.
PROCEDURE
1. Test fresh, well-mixed, uncentrifuged urine.
2. Remove one reagent strip. Recap the bottle promptly. Briefly (no longer than 1 second) dip test strip into the urine. Ensure that the chemically impregnated patches on the test strip are totally immersed.
3. Draw the edge of the strip over the rim of the specimen container to remove excess urine.
4. Turn the test strip on its side and tap once on a piece of absorbent paper to remove any remaining urine, and to prevent the possible mixing of chemicals.
5. After the appropriate time read the test as follows: hold strip close to color blocks and match carefully, ensuring that the strip is properly oriented to the color chart on the vial label.
The chemical analysis of urine is a vital part of the routine urinalysis. The Chemstrip 10SG urine test strips are inert plastic strips to which are attached different chemically impregnated test sites on an absorbent pad for determining specific gravity, pH, leukocytes, nitrite, protein, glucose, ketones, urobilinogen, bilirubin, and blood/hemoglobin in urine. Refer to the package insert for the specific test principles and parameters. When the dry reagents come in contact with urine or a suitable control solution, the reagents are activated and a chemical reaction occurs. The chemical reaction is a specific color change. This is observed visually and compared with a special color chart provided by the manufacturer. The intensity of the color formed is generally proportional to the amount of substance present in the specimen at a specific time. Some tests are used as screening tests (presence or absence) while others are used to estimate (semiquantitate) the amount of substance present and reported in a plus system or in numerical values.
SPECIMEN
Fresh, uncentrifuged, well mixed urine or QC solutions at room temperature.
1. Patient Preparation—N/A
2. Type
Random specimens
First morning void – most concentrated
Timed specimens (such as complete 24-hour collections
Double-voided specimens
Midstream-voided specimens (used for routine urinalysis)
Clean-catch midstream – specimen of choice
Catheterized urine – performed when the patient has dysuria or is incontinent.
The patient should receive oral and detailed written instructions for the desired urine collection technique. See urine specimen collection procedure.
3. Handling Conditions—Specimens should be tested within one hour of collection or immediately refrigerated at 2-8oC.
4. Rejection criteria for samples
Specimens without acceptable labels.
Discrepant information on labels and requisitions.
Insufficient quantity for test requested (1mL or less)
Grossly contaminated (i.e. foreign materials, fecal matter) are to be rejected for testing.
EQUIPMENT AND MATERIALS
1. Equipment
Timer
2. Materials
Chemstrip 10SG dipsticks
3. Preparation—If this is the first specimen of the day, perform QUALITY CONTROL.
4. Performance Parameters—N/A
5. Storage Requirements
· The Chemstrip 10SG dipsticks must be kept in tightly capped or stoppered containers. Strips will deteriorate when exposed to moisture, direct sunlight, heat, or volatile substances.
· Do not remove the desiccant from the container. Store at room temperature.
· Remove only the number of strips needed at a time, and keep the container tightly closed at all times. Do not touch test areas.
CALIBRATION – N/A
QUALITY CONTROL
Quality control testing with 2 levels of liquid control material (Bio Rad Liquichek level 1 & 2 Controls) should be conducted prior to daily testing. Distilled water may be used as a negative control. The control system is used to determine accuracy and precision in the measurement of the physical and chemical tests commonly employed in semiquantitative urine testing. Quality control results must be recorded and available for reference.
1. If the product has been refrigerated, warm one vial of each level of control to room temperature, 18o-30oC (15-30 minutes). Verify that the lot number indicated on each control bottle matches the assay sheet enclosed.
2. Remove the dropper tip cap. Holding the dipstick reagent strip in one hand, invert the control bottle and apply control material directly across each pad by gently squeezing the bottle.
3. Remove excess control by tilting the dipstick on its edge and blotting on an absorbent towel.
4. If reading the results visually, follow the manufacturer’s instructions completely, comparing the color reactions at the designated times to the appropriate strip area.
5. Wipe the tip of the control bottle and recap.
6. Control stability—The Bio Rad control is stable after opening for 31 days at room temperature. When refrigerated, the product is stable until it’s expiration date. Freeze aliquots of each control before the expiration date for use after the material has expired.
7. Record the reaction of each test on the appropriate quality control chart.
Proficiency Testing: Successful participation in the USDOS PT Program.
PROCEDURE
1. Test fresh, well-mixed, uncentrifuged urine.
2. Remove one reagent strip. Recap the bottle promptly. Briefly (no longer than 1 second) dip test strip into the urine. Ensure that the chemically impregnated patches on the test strip are totally immersed.
3. Draw the edge of the strip over the rim of the specimen container to remove excess urine.
4. Turn the test strip on its side and tap once on a piece of absorbent paper to remove any remaining urine, and to prevent the possible mixing of chemicals.
5. After the appropriate time read the test as follows: hold strip close to color blocks and match carefully, ensuring that the strip is properly oriented to the color chart on the vial label.
Specific Gravity 60 sec Glucose 60 sec
pH Immediate Ketones 60 sec
Leukocytes 60-120 sec Urobilinogen 10-30 sec
Nitrite 30 sec Bilirubin 30-60 sec
Protein 30-60 sec Blood 60 sec
For convenience, all values on the strip may be read between 1 and 2 minutes after immersion in the urine. The colors are stable up to 120 seconds after immersion in the urine. Color changes that occur after 2 minutes from immersion are not of clinical value. Color changes that occur only along the edge of the test area should be ignored.
CALCULATIONS – N/A
REPORTING RESULTS
1. Reference Ranges—Normal Urine Values
Glucose Negative
Bilirubin Negative
Ketones Negative
Specific Gravity 1.010-1.025
Blood Negative
PH 4.5-8.0
Protein Negative-Trace
Urobilinogen 1EU/dL or less
Nitrite Negative
Leukocyte Negative
2. Procedures for Abnormal Results
If any of the above tests fail to fall within the acceptable normal ranges, they must have the appropriate confirmatory tests performed and recorded on the result slip prior to reporting results.
Chemistrip Dipstick Test Confirmatory Test
Glucose Clinitest
Bilirubin Ictotest
Ketones Acetest*
Specific Gravity Refractometer
Blood Microscopic
pH pH
Protein SSA
Urobilinogen None
Nitrite Microscopic
Leukocytes Microscopic
LIMITATIONS
The limitations including interfering substances for each reagent are shown below.
1. Specific Gravity—Results may vary between urine concentration measuring methodologies due to their differing principles and limitations. Urines above 1.025 are not reliably measured with correct relative ionic concentration methodology. Test samples with results above 1.025 should be retested with a refractometer. The chemical principle of this test may also cause slightly different results compared with other urine concentration measuring methods when elevated amounts of certain urine constituents are present. Glucose and urea concentrations greater than 1% may cause a low specific gravity reading relative to other methods. In the presence of moderate amounts of protein (100-500 mg/dL) or ketoacidosis, readings tend to be elevated.
2. pH Test—No known interference’s when handled according to instructions
3. Leukocytes Test—Test is not affected by erythrocytes in concentration up to 10,000/ul or by bacteria common in urine. Specimens should not be collected in containers that have been cleaned with strong oxidizing agents. Do not use preservatives. The drugs cephalexin and gentamicin have been found to interfere with this test. In addition nitrofurantoin colors the urine and this effect interferes with visual interpretation of the test strip. High levels of albumin (> 500 mg/dL) in the urine may interfere with the test results.
4. Nitrite Test—Large amounts of ascorbic acid decrease the sensitivity of the test. False-positive readings may be produced by medication that colors the urine red or which turns red in an acid medium (e.g. phenazopyridine)
5. Protein Test—False-positive results may be found:
· In strongly basic urine (pH 9 or higher)
· During therapy with phenazopyridine
· When infusions of polyvinylpyrrolidone (blood substitutes) are administered
· When residues of disinfectants containing quaternary ammonium groups or chlorohexidine are present in the urine container
6. Glucose Test—The effect of ascorbic acid (vitamin C) retained in the urine due to ingestion of vitamin tablets, antibiotics or fruit juices has been eliminated at glucose concentrations of 100 mg/dL and above so that false-negative readings may only rarely occur, even at high concentration of ascorbic acid. False-positive readings may be produced by strong oxidizing cleaning agents in the urine container.
7. Ketone Test—Red-orange to red color shades, which are, however readily distinguishable form the colors obtained with ketone bodies can be produced by phenylketone or phthalein compounds that be administered for liver and kidney function tests. Mercaptoethane sulphonate sodium or other sulfhydryl containing compounds may cause false-positives.
8. Urobilinogen Test—The total absence of urobilinogen cannot be detected. Most normal urines give a slight pink reaction. The test gives the same color reaction with urobilinogen as with stercobilinogen; however, the differentiation is not of diagnostic importance. Urine treated with phenazopyridine may show a false-positive reaction. Nitrite concentrations above 5 mg/dl or formalin concentrations above 200 mg/dL (as preservative) may cause a decrease in the color reaction.
9. Bilirubin Test—Large amounts of ascorbic acid present in the urine following the ingestion of vitamin C or fruit juices lower the sensitivity of the test. In case of doubt, the test should be repeated on the urine voided at least 10 hours after the last administration of vitamin C. Elevated concentrations of nitrite, as in urinary tract infections, may result in lower bilirubin values. Large amounts of urobilinogen in the urine affect the color change of the bilirubin test, but not enough to give a positive result. False-positives readings may be produced by medication that colors the urine red, or which turns red in acid medium.
10. Blood Test—False-negative readings are obtained when formalin is used to preserve the urine. Nitrite in excess of 10 mg/dL in the urine (which is rare in urinary tract infections) delays the reaction. False-positive results can be produced by residues of strongly oxidizing cleaning agents in the urine container. Urine from menstruating females will occasionally yield a positive result. This test has not been found to be affected by the ingestion of reasonable quantities of ascorbic acid.
REFERENCES
1. Clinical Diagnosis and Management by Laboratory Methods, 18th ed., 1995, pg. 431-432, by J.B. Henry.
2. Chemstrip 10SG by ROCHE package insert.
3. Urinalysis and Body Fluids, 1995, by Karen Munson Ringsrud and Jean Jorgenson Linne.
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