Chemical-Examination-part-1.pdf

Chemical Examination of Urine Prepared by: Monica Ferreria, RMT,DTA,MPH Commercial reagent strips currently provide a simple, rapid means for performing medically significant chemical analysis of urine, including pH protein glucos...

Chemical Examination of Urine Prepared by: Monica Ferreria, RMT,DTA,MPH Commercial reagent strips currently provide a simple, rapid means for performing medically significant chemical analysis of urine, including pH protein glucose ketones False negative: BBLNG blood o Blood bilirubin o Bilirubin urobilinogen o Leukocyte nitrite o Nitrite leukocytes o Glucose specific gravity 2 MAJOR TYPES OF REAGENT TYPES A. Multistix (Siemens Healthcare Diagnostics, Inc., Tarrytown, NY) B. Chemstrip (Roche Diagnostics, Indianapolis, IN) 2 mdferreria,RMT,DTA,MPH  Reagent Strips ➔ It consist of chemical-impregnated absorbent pads attached to a plastic strip. ➔ A color producing chemical reaction takes place when the absorbent pad comes in contact with urine. ➔ The reactions are interpreted by comparing the color produced on the pad within the required time frame with a chart supplied by the manufacturer 3 mdferreria,RMT,DTA,MPH - By careful comparison of the colors on the chart with the strip, a semiquantitative value of trace, 1+, 2+, 3+, or 4+ can be reported. - Automated reagent strip readers uses REFLECTANCE PHOTOMETRY also provide Système International (SI) units. mdferreria,RMT,DTA,MPH Reagent Strip Technique 1. Dip the reagent strip briefly into a well-mixed, uncentrifuged urine specimen at room temperature. 2. Remove excess urine by touching the edge of the strip to the container as the strip is withdrawn. 3. Blot the edge of the strip on a disposable absorbent pad. 4. Wait the specified amount of time for the reaction to occur. 5. Compare the color reaction of the strip pads to the manufacturer’s color chart in good lighting. 6. Read the results at the correct time, and5record the results. mdferreria,RMT,DTA,MPH Care of Reagent Strips 1. Store with desiccant in an opaque, tightly closed container. 2. Store below 30°C; do not freeze. 3. Do not expose to volatile fumes. 4. Do not use past the expiration date. 5. Do not use if chemical pads become discolored. 6. Remove strips immediately before use. 6 mdferreria,RMT,DTA,MPH Technique 1. Mix specimen well. 2. Let refrigerated specimens warm to room temperature before testing. 3. Dip the strip completely, but briefly, into the specimen. 4. Remove excess urine by withdrawing the strip against the rim of the container and by blotting the edge of the strip. 5. Compare reaction colors with the manufacturer’s chart under a good light source at the specified time. 6. Perform confirmatory tests when indicated. 7. Be alert for the presence of interfering substances. 8. Understand the principles and significance of the test; read package inserts. 9. Relate chemical findings to each other and to the physical and microscopic urinalysis results. 7 mdferreria,RMT,DTA,MPH Quality Control 1. Test open bottles of reagent strips with known positive and negative controls per facility protocol or every 24 hours.. 2. Resolve control results that are out of range by further testing. 3. Test reagents used in confirmatory tests with positive and negative controls. 4. Perform positive and negative controls on new reagents and newly opened bottles of reagent strips. 5. Record all control results and reagent lot numbers. 8 mdferreria,RMT,DTA,MPH  Errors Caused by Improper Technique 1. Formed elements, such as red and white blood cells, sink to the bottom of the specimen and will be undetected in an unmixed specimen. 2. Allowing the strip to remain in the urine for an extended period may cause leaching of reagents from the pads. 3. Allowing excess urine to remain on the strip after its removal from the specimen can produce a runover between chemicals on adjacent pads, producing distortion of the colors. To ensure against runover, blotting the edge of the strip on absorbent paper and holding the strip horizontally while comparing it with the color chart is recommended. 9 mdferreria,RMT,DTA,MPH 4. The timing for reactions to take place varies between tests and manufacturers and ranges from 30 seconds to 120 seconds for leukocyte esterase (LE). - when precise timing cannot be achieved, manufacturers recommend that reactions be read between 60 and 120 seconds, with the LE reaction read at 120 seconds. 5. A good light source is essential for accurate interpretation of color reactions. 6. The strip must be held close to the color chart without actually being placed on the chart. 7. Reagent strips and color charts from different manufacturers are not interchangeable. 8. Specimens that have been refrigerated must be allowed to return to room temperature before reagent strip testing, as the enzymatic reactions on the strips are temperature dependent. 10 mdferreria,RMT,DTA,MPH  pH A healthy individual usually produces a first morning specimen with a slightly acidic pH of 5.0 to 6.0; A more alkaline pH is found after meals (alkaline tide). 4.5 to 8.0 - pH of normal random specimens. No normal values are assigned to urinary pH, The pH of freshly excreted urine does not reach above 8.5 in normal or abnormal conditions. ○ A pH above 8.5 is associated with a specimen that has been preserved improperly and indicates that a fresh specimen should be obtained to ensure the validity of the analysis. 11 mdferreria,RMT,DTA,MPH Causes of Acid and Alkaline Urine Acid Urine Alkaline Urine Emphysema Hyperventilation Diabetes mellitus Vomiting Starvation Renal tubular acidosis Dehydration Presence of urease producing Diarrhea bacteria Presence of acid-producing Vegetarian diet bacteria (Escherichia coli) Old specimens High-protein diet Cranberry juice Medications (methenamine mandelate [Mandelamine], fosfomycin tromethamine [Monurol]) mdferreria,RMT,DTA,MPH PRINCIPLE Double indicator system REAGENTS Multistix and Chemstrip: Methyl red Bromthymol blue SENSITIVITY pH 5-9 / Multistix: 5.0–8.5 in 0.5 increments visually; 5.0–9 instrumentally Chemstrip: 5.0–9.0 in 1.0 increments SOURCES OF ERROR/INTERFERENCE No known interfering substances. Runover from adjacent pads Old specimens Bacterial growth CLINICAL SIGNIFICANCE Respiratory or metabolic acidosis/ketosis Renal or metabolic alkalosis Defects in renal tubular secretion and reabsorption of acids and bases—renal tubular acidosis Renal calculi formation and prevention Treatment UTI Precipitation/identification of crystals Determination of unsatisfactory specimen CORRELATIONS WITH OTHER TESTS 13 Microscopic Nitrite, Leukocytes and mdferreria,RMT,DTA,MPH Note: Care must be taken to prevent runover between the pH testing area and the adjacent, highly acidic protein testing area on Multistix, as this may produce a reading that is falsely acidic in an alkaline urine 14 mdferreria,RMT,DTA,MPH  PROTEIN ➔ The most indicative of renal disease is the protein determination. Proteinuria is associated with early renal disease. ➔ NORMAL URINE: