Chemstrip Urine Test Strips from Roche Diagnostics are multiparameter visual reagent strips that are used to measure certain constituents in the urine. These measurements are useful in the evaluation of renal, urinary, and metabolic disorders. Chemstrip Urine Test Strips are clinically proven to resist vitamin C interference. All reagent pads may be simultaneously read between 1 and 2 minutes. Chemstrip urine test strips are packaged in a vial with a tightly fitting cap, that contains a drying agent. Each test strip is stable and ready for use when removed from the vial. No additional instrumentation is required.

Intended use

Urine test strips for specific gravity, pH, leukocytes, nitrite, protein, glucose, ketones, urobilinogen, bilirubin, blood, and hemoglobin. Chemstrip 2 GP, Chemstrip 2 LN, Chemstrip 9 and Chemstrip 10 with SG urine test strips are intended for use visually.

The different Chemistrip Variants perform the following set of tests:

Results

Results are obtained by direct visual comparison with the color scale printed on the vial label label by always assigning the value of the nearest color block. No calculations are necessary. The visual color chart is not intended to represent quantitative findings and serves only as a screening mechanism. If quantitative results are desired, it is recommended that further testing of the urine be carried out utilizing a reference procedure.

Limitations - interference

The limitations including interfering substances for each reagent are shown below.

Specific Gravity:Results may vary between urine concentration measuring methodologies due to their differing principles and limitations.19 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.

pH Test:No known interferences when handled according to instructions.

Leukocyte Test:This test is not affected by erythrocytes in concentrations up to 10,000/μL 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 and urinary glucose excretion in excess of 1 g/dL may interfere with the test results. Studies show that formaldehyde (stabilizer) and medication with imipenem, meropenem and clavulanic acid may cause false‑positive reactions.

Nitrite Test:Large amounts of ascorbic acid (see under glucose) 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).

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, and when residues of disinfectants containing quaternary ammonium groups or chlorohexidine are present in the urine container.

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.

Ketone Test:Phenylketone or phthalein compounds that may be administered for liver and kidney function tests can produce red-orange to red color shades, which are, however, readily distinguished from the colors obtained with ketone bodies. 2‑Mercaptoethane sulfonate sodium (MESNA) or other sulfhydryl-containing compounds may cause false‑positive results.

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 from patients who are being treated with phenazopyridine may show a false‑positive reaction. Nitrite concentrations above 5 mg/dL or formalin concentrations above 200 mg/dL (as a preservative) may cause a decrease in the color reaction.

Bilirubin Test:Large amounts of ascorbic acid present in urine following the ingestion of medication containing vitamin C or fruit juices lower the sensitivity of the test. In case of doubt, the test should be repeated on 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‑positive readings may be produced by medication that colors the urine red, or which turns red in an acid medium (e.g. phenazopyridine).

Blood/Hemoglobin 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. For diagnostic purposes, the results should always be assessed in conjunction with the patient?s medical history, clinical examination and other findings.

Expected values

Specific Gravity: Random urines vary from 1.001‑1.035. Twenty‑four hour urines from normal adults with normal diets and fluid intake will have a specific gravity of 1.016‑1.022.19

pH:Urine pH values generally range from 5 to 9 units. The most frequent pH values for the first morning specimens in healthy subjects are between pH 5 and 6.

Leukocytes:Normal urines should produce no color reaction. A ?trace? finding indicates a possible borderline situation, and it is recommended that the test be repeated on a fresh urine sample from the same patient. Positive and repeated trace findings indicate the need for further testing of the patient and/ or urine sample in accordance with the medically accepted procedures for pyuria.

Nitrite: A concentration as low as 0.05 mg/dL of nitrite will produce a slightly pink coloration of the test pad. This indicates a positive result.

Protein: A color change from yellow to light green/green will occur if protein is present in urine. The concentrations given on the vial label correspond with the albumin concentration in urine. Pathological proteinuria will usually produce persistent values above 30 mg/dL. Clinical significance of the trace result should be determined by additional testing.

Glucose:Due to the test?s sensitivity, glucose should not be detectable in normal urine. Therefore, any positive reaction should be followed by further diagnostic evaluation of the patient, such as a quantitative blood glucose or a glucose tolerance test.

Ketones:Ketone bodies should not be detected in normal urine with this test. Fasting or starvation diets may cause positive indications. In known pathological conditions such as diabetes, the presence of ketones may be useful as an index of metabolic status.

Urobilinogen: Concentrations are usually greater in the afternoon than during the remainder of the day. Values up to 1 mg/dL are usually considered normal.

Bilirubin: In normal urine, bilirubin should not be detectable. However, this test is very sensitive to bilirubin (0.5 mg/dL will produce positive results) and any positive reaction indicates that further diagnostic evaluation of the patient is needed.

Blood/Hemoglobin:A trace result is equivalent to 5‑10 Ery/μL. Erythrocyte excretion up to 5 Ery/μL may be expected in normal urine. 16,17 Levels above this certainly warrant further diagnostic evaluation of the patient. Each laboratory should investigate the transferability of the expected values to its own patient population and if necessary determine its own reference ranges.

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