4. a. If reading visually, compare reagent areas to corresponding color chart on the bottle label at the times specified. Hold strip close to color blocks 74 Concise Book of Medical Laboratory Technology: Methods and Interpretations and match carefully. Avoid laying the strip directly on the Color Chart, as this will result in the

 

Ketone

This test is based on the development of colors ranging

from buff-pink, for a negative reading, to purple when

acetoacetic acid reacts with nitroprusside.

Specific Gravity

This test is based on the apparent pKa change of

certain pretreated polyelectrolytes in relation to ionic

concentration. In the presence of an indicator, colors range

from deep blue-green in urine of low ionic concentration

through green and yellow-green in urines of increasing

ionic concentration.

Blood

This test is based on the peroxidase-like activity of hemoglobin,

which catalyzes the reaction of disopropylbenzene dihydroperoxide and 3.3’, 5, 5’-tetramethylbenzidine. The resulting

color ranges from orange through green; very high levels

of blood may cause the color development to continue to

blue.

pH

The test is based on the double indicator principle that

gives a broad range of color covering the entire urinary pH

range. Colors range from orange through yellow and green

to blue.

Protein

This test is based on the protein-error-of-indicators

principle. At a constant pH, the development of any green

color is due to the presence of protein. Colors range from

yellow for “Negative” through yellow-green and green to

green-blue for “Positive” reactions.

Urobilinogen

This test is based on a modified Ehrlich reaction, in which

ρ-diethylaminobenzaldehyde in conjunction with a color

enhancer reacts with urobilinogen in a strongly acid

medium to produce a pink-red color.

Reagents

(Based on dry weight at time of impregnation):

Glucose

2.2% w/w glucose oxidase (microbial, 1.3 IU); 1.0% w/w

peroxidase (horseradish, 3300 IU); 8.1% w/w potassium

iodide; 69.8% w/w buffer; 18.9% w/w non-reactive

ingredients.

Bilirubin

0.4% w/w 2, 4-dichloroaniline diazonium salt; 37.3% w/w

buffer; 62.3% w/w non-reactive ingredients.

Ketone

7.1% w/w sodium nitroprusside; 92.9% w/w buffer.

Specific Gravity

2.8% w/w bromothymol blue; 68.8% w/w poly (methyl vinyl

ether/maleic anhydride); 28.4% w/w sodium hydroxide.

Blood

6.8% w/w disopropylbenzene dihydroperoxide; 4.0% w/w

3.3’, 5, 5’-tetramethylbenzidine; 48.0% w/w buffer; 41.2%

w/w non-reactive ingredients.

Urine Analysis 73

pH

0.2% w/w methyl red; 2.8% w/w bromothymol blue; 97.0%

w/w non-reactive ingredients.

Protein

0.3% w/w tetrabromophenol blue; 97.3% w/w buffer; 2.4$

w/w non-reactive ingredients.

Urobilinogen

0.2% w/w ρ-diethylaminobenzaldehyde; 99.8% w/w nonreactive ingredients.

Warning and Precautions

Bayer reagent strips are for in vitro diagnostic use.

Storage

Storage below 30°C in a cool, dry place. Do not refrigerate.

Keep out of direct sunlight. Do not use after expiration

date.

Recommended Procedures for Handling

Roche Reagent Strips

All unused strips must remain in the original bottle.

Transfer to any other container may cause reagent strips

to deteriorate and become unreactive. Do not remove

desiccant (s) from bottle. Do not remove strip from

the bottle until immediately before it is to be used

for testing. Replace cap immediately and tightly after

removing reagent strip. Do not touch test areas of the

reagent strip. Work areas and specimen containers

should be free of detergents and other contaminating

substances.

Dip test areas in urine completely, but briefly, to avoid

dissolving out the reagent. If using strips visually, read

test results carefully at the time specified, in a good light

(such as fluorescent) and with the test area held near the

appropriate color chart on the bottle label. Do not read

the strips in direct sunlight. If the strips are used instrumentally, carefully follow the directions given in the

appropriate instrument-operating manual.

Important

Protection against ambient moisture, light and heat is essential

to guard against altered reagent reactivity. Discoloration

or darkening of reagent areas may indicate deterioration.

If this is evident, or if test results are questionable or

inconsistent with expected findings, the following steps are

recommended:

1. Confirm that the product is within the expiration date

shown on the label;

2. Check performance against known negative and

positive control materials (e.g. Chek-stix Control

Strips);

3. Retest with fresh product. If proper results are not

obtained, consult your local product representative

for advice on testing technique and results.

Specimen Collection and Preparation

Collect urine in a clean container and test it as soon as

possible. Do not centrifuge. The use of urine preservatives

is not recommended. If testing cannot be done within an

hour after voiding, refrigerate the specimen immediately

and let it return to room temperature before testing.

It is especially important to use fresh urine to obtain

optimal results with the tests for bilirubin and urobilinogen,

as these compounds are very unstable when exposed to

room temperature and light.

Prolonged exposure of urine to room temperature may

result in microbial proliferation with resultant changes in

pH. A shift to alkaline pH may cause false positive results

with the protein test area. Urine containing glucose may

decrease in pH as organisms metabolize the glucose.

Bacterial growth from contaminating organisms may

cause false positive blood reactions from the peroxidases

produced.

Contamination of the urine specimen with skin

cleansers containing chlorhexidine may affect protein

(and to a lesser extent specific gravity and bilirubin) test

results. The user should determine whether the use of such

skin cleansers is warranted.

Procedure

Must be followed exactly to achieve reliable test results:

1. Collect fresh urine specimen in a clean, dry container.

Mix well immediately before testing.

2. Remove one strip from bottle and replace cap.

Completely immerse reagent areas of the strip in fresh

urine and remove immediately to avoid dissolving out

reagents.

3. While removing, run the edge of the entire length of the

strip against the rim of the urine container to remove

excess urine. Hold the strip in a horizontal position to

prevent possible mixing of chemicals from adjacent

reagent areas and/or contaminating the hands with

urine.

4. a. If reading visually, compare reagent areas to corresponding color chart on the bottle label at the

times specified. Hold strip close to color blocks

74 Concise Book of Medical Laboratory Technology: Methods and Interpretations and match carefully. Avoid laying the strip directly on the Color Chart, as this will result in the

urine soiling the chart.

b. If reading instrumentally, carefully follow the

directions given in the appropriate instrumentoperating manual.

Proper read time is critical for optimal results. If using

strips visually, read the glucose and bilirubin tests at 30

seconds after dipping. Read the ketone test at 40 seconds;

the specific gravity test at 45 seconds; pH, protein,

urobilinogen and blood at 60 seconds. The pH and protein

areas may also be read immediately or at any time up to 2

minutes after dipping.