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Principle: | Clinical Significance: | Specimen: | Materials | Reagents: | Standardization: N.A. | Procedure: | Results Derivation: | Expected Result(s) | Quality Control: | References:

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Common Interferences

I. Principle:

Fresh urine is analyzed for selected chemical constituents and physical properties using reagent impregnated strips and other semiquantitative techniques.
Urinalysis Chemical Screen (094): Includes gross exam and chemical screen only.
Urinalysis with Microscopy (090): Includes gross exam, chemical screen and microscopic exam.
Acetone, Random Urine (093): Report only the ketone constituent using the N-Multistix 10SG.

II. Clinical Significance:

The routine urinalysis is a basic screening test for renal/urinary tract or systemic disease.

III. Specimen:

  1. First voided morning specimens are preferred since they are more concentrated.
  2. All urines are collected in a clean container with a tight fitting lid.
  3. Urines must be properly identified with two patient identifiers, date and time of collection, and initials of person collecting the specimen. A label should be attached around the side of the urine specimen container, not its lid. (Refer to: “Specimen Handling, Identification & Rejection” protocols in the Quality Assurance Manual.)
  4. Clean catch, clean voided, sterile, etc. urines must be identified as such.
  5. It is very important that urine specimens be transported to the lab as soon as possible for prompt analysis. Urine specimens should be screened from strong light and may be held from the time of collection for up to 2 hours at room temperature. If the delay between collection and analysis will be greater than 2 hours, the specimen may be refrigerated at 2 to 8°C for up to 4 hours.
    Urine specimens must not be refrigerated for more than 4 hours.
    Any specimen that has not been refrigerated and is more than 2 hours old upon arrival in the laboratory or is past 4 hours from the time of collection may be rejected. (Consult with a pathologist.)
  6. Minimum specimen volumes:
    1. Pediatric (< 2 years): 3 ml
    2. Patient ≥2 years of age: 5 ml
    3. Specimens less than minimum volumes can be used. These specimens are reported with a disclaimer “Testing results may be altered by small sample volume (state volume). Clinical correlation is needed and repeat testing with a larger sample volume is recommended if clinically indicated”.

IV. Materials

  1. Centrifuge tubes, 12 ml disposable, conical, graduated (Fisher #14-377-63)
    MA (Fisher 14-375-20)
  2. Plastic transfer pipette, 6 inch (CardinalHealth #P5214-12)
    MA (Fisher 13-711-5A)
  3. Coverslips, 22 x 22mm, #1 thickness (Surgipath #105)
    MA (Purchasing MC050)
  4. Glass slides, plain (Surgipath #220)
    MA (Purchasing MM009)
  5. Centrifuge
  6. Microscope
    Our defacto standard for microscope field # is based on a field size defined by a fixed ocular diaphragm of 18 mm diameter. In order to obviate the need for scope-specific procedures, the scopes with larger field of view have been corrected to the standard by means of a custom reticle that has been installed in the right-side oculars. The reticle superimposes a thin circle over the visible field. When counting formed elements, count only those target elements, which fall within the circle.

V. Reagents:

  1. Siemens Multistix 10SG Urinalysis Reagent Strip (CardinalHealth #U2604-2)
  2. Lysing reagent for RBC; Zap Oglobin (Beckman #754638)
    Note: Stephens Scientific “Manual Lyse” is the only acceptable red cell lysing reagent. There is a distinct reaction difference between Stephens Scientific and other lysing reagents. Other products tend to be considerably slower. The degree of difference is dependent on reagent lot.

VI. Standardization: N.A.

VII. Procedure:

  1. Preparing the specimens:
    1. Match specimen container with appropriate requisition.
    2. Place an accession number from the requisition on the urine container and on a centrifuge tube.
    3. Transcribe the date and time collected from the container onto the requisition. Either record the time of analysis on the requisition or punch the requisition on the timeclock as soon as the analysis is complete.
    4. Mix the specimens well by gently swirling.
    5. Match the I.D. number of specimen and requisition at the time of the analysis of each specimen.
  2. Gross Examination:
    1. Using the 10 ml graduated mark on the centrifuge tube as a guide, pour off a 10 ml aliquot of the well-mixed specimen into the appropriately identified centrifuge tube. If only a minimum volume of urine is received, pour the entire specimen into the tube. Always leave one drop of urine in the container for possible urine culture.
    2. Examine the urine in the tube and determine its color and appearance. Refer to Section VIII. 1. A. (Color) and B. (Appearance). Record the results on the requisition.
  3. Chemical Examination:
    1. Manual Method:
      1. Completely immerse all reagent areas of a urinalysis reagent strip in the fresh, well-mixed, uncentrifuged urine and remove immediately to avoid eluting out reagents.
      2. While removing, run the edge of the strip against the rim of the urine container to remove excess urine. Holding the strip in a horizontal position with flat surfaces vertical to prevent possible mixing of chemicals from adjacent reagent areas and/or soiling of hands with urine, draw edge of reagent strip across a paper towel. Avoid contact between reagent areas and paper towel.
      3. Compare test areas to corresponding color charts on the bottle label at the times specified. Set a timer if needed. Hold strip close to color block and match carefully.
        1. Glucose: Read at 30 seconds. Grade as N (Negative), T, 1+, 2+, 3+ or 4+.
        2. Bilirubin: Read at 30 seconds. If positive result is obtained, refer to Section VIII. 2. B..
        3. Ketone: Read at 40 seconds. Grade as N (Negative), T, 1+, 2+, 3+ or 4+.
        4. Specific Gravity: Read at 45 seconds. Report numerical value.
          0.005 must be added to the Specific Gravity results when samples read visually with pH ≥ 6.5.
        5. Blood: Read at 60 seconds. Grade as N (Negative), T, 1+, 2+ or 3+.
        6. pH: Read at 60 seconds. Report numerical value.
        7. Protein: Read at 60 seconds. Grade as N (Negative), T, 30, 100, > 300.
        8. Urobilinogen: Read at 60 seconds. Report numerical value.
        9. Nitrite: Read at 60 seconds. Report as N (Negative) or P (Positive).
        10. Leukocyte Esterase: Read at 2 minutes. Grade as N (Negative) T, 1+, 2+ or 3+.
          Note: A positive reaction at less than 2 minutes may be regarded as a positive indication of leukocytes in urine. Color changes that occur after 2 minutes are not valid.
    2. Automated Method (Clinitek)
      Refer to the “
      Clinitek STATUS; Operate” procedure.
    3. Refer to Evaluation of Common Interferences table at the end of this section.
  4. Microscopic Examination:
    1. Centrifuge the specimen from Section VII. 2. at 400 rcf for 5 minutes.
    2. Using the 0.5 ml graduated mark on the centrifuge tube as a guide, decant the supernatant of each specimen to the 0.5 mark.
      If minimum specimen volumes are used decant to the 0.25 ml mark and record on the requisition the quantity of the specimen submitted.
    3. With a transfer pipette, gently mix the sediment with the residual supernatant by flushing in and out of pipette several times. Use a separate pipette for each specimen.
    4. Holding the pipette in a perpendicular position to the surface, transfer one drop from each concentrated specimen to a glass slide. Two microscopic preparations can be performed on a single slide.
    5. Place one standard coverslip squarely over the drop and wait a few seconds before commencing with the microscopic examination.
    6. An adequate microscopic examination requires a minimum of 10 fields to be examined at low and high dry powers.
    7. Because of the low refractive index of some formed elements such as hyaline casts, microscopic exam is performed with a lowered substage condenser or with phase contrast. Refer to Section VIII. 3 and 4 for the proper format for reporting results.
    8. Investigate any discrepancy between the microscopic examination and the macroscopic results.

Evaluation of Common Interferences


VIII. Results Derivation:

  1. Gross Examination:
    1. Color:
      1. Color of urine is dependent upon many factors. Normally it is yellow colored due to the presence of several pigments, especially urochrome.
        Substances that cause abnormal urine color may affect the readability of reagent areas on the urinalysis reagent strips. The color development on the reagent pad may be masked, or a color reaction may be produced on the pad that could be interpreted visually and/or instrumentally as a false positive.
        Refer to the table “
        Evaluation of Common Interferences”.
      2. When heavily pigmented sediment is present in a specimen, centrifuge the specimen at 400 rcf for 5 minutes and analyze the reagent strip on the supernatant. If there is still a problem with suspected false positives, a disclaimer must be applied to the results: "Disclaimer - False positive chemistry results may occur due to heavy pigmentation."
      3. The intensity of the color depends upon the concentration of the urine. Dilute urine is usually pale; whereas, concentrated urine is darker. Acidic urine is usually darker than alkaline urine.
      4. Colors generally seen and their abbreviations are:
        1. Yellow: YEL
        2. Brown: BRN
        3. Green: GRN
        4. Orange: ORG
        5. Red: RED
        6. Blue: BLU
      5. Some indicative colors are as follows:
        1. Brown: Hemoglobin, Bilirubin, Melanin, and Homogentisic Acid
        2. Green: Bilirubin derivatives or Drugs
        3. Orange: Drug (Pyridium)
        4. Red: Blood, Porphyrin, Hemoglobin, myoglobin or heavy intake of food pigments (beets)
    2. Appearance:
      1. Freshly voided normal urine is clear or transparent. On cooling or standing specimens tend to develop a faint cloud of mucous and epithelial cells that settle to the bottom (nebecula).
      2. Appearances generally seen and their abbreviations are:
        1. Clear: (No obvious cloudiness) CLR
        2. Hazy: (Slightly cloudy) HAZ
        3. Cloudy: (Cloudy) CLD
        4. Turbid: (Very cloudy) TBD
      3. Normal substances causing cloudiness are: amorphous phosphate, amorphous urate and many calcium oxalate crystals.
      4. Abnormal substances causing cloudiness are: increased numbers of epithelial cells, white blood cells, red blood cells, bacteria and fat particles.
  2. Chemical Examination:
    1. All negative results are reported as N.
    2. Positive Bilirubin is confirmed with the Ictotest procedure. (Refer to: “Ictotestprocedure.) Report Ictotest results only.
  3. Microscopic Examination: Low Power
    Note: Refer to “Urinary Sediment: A Textbook Atlas” by Meryl H. Haber, © 1981, to insure consistency of morphologic observations among all personnel.
    1. Scan on low power for presence of casts. Identify type on high power but report number and type per low power field (LPF). Grade < 1/LPF, 1-50/LPF, > 50/LPF if present.
    2. Note presence of mucus and grade Trace, 1+, 2+, 3+, 4+ if present.
    3. Scan on low power for presence of crystals, but evaluate type and grade on high power. Grade Trace, 1+, 2+, 3+, 4+ if present.
  4. Microscopic Examination: High Power
    Note: Refer to “Urinary Sediment: A Textbook Atlas” by Meryl H. Haber, © 1981, to insure consistency of morphologic observations among all personnel.

    Results of the micro exam are reported as follows:
    1. RBC (# per HPF):
      1. 0 (negative): no RBCs seen
      2. <1 (numerical value): number of RBCs counted
      3. 1 - 50 (numerical value): number of RBCs counted
      4. >50 (many RBCs seen): more than 50 RBCs seen (too numerous to count)
        Note: If there is a full field or packed field of RBCs making it difficult to identify other formed elements, the RBCs may be lysed. Add 1 drop of lyse to one drop of urine sediment on a slide. Mix with wooden applicator stick and add coverslip. The slide should be scanned before the addition of lyse to enumerate RBC and to look for presence of RBC casts as they will disintegrate when lyse is added. It is also helpful to add lyse when in doubt if formed elements are RBCs or yeast. Yeast will not dissolve when lyse is added.
    2. WBC (# per HPF): The same criteria used in reporting RBCs is used in reporting WBCs.
    3. Epithelial Cells: Evaluate and grade Trace, 1+, 2+, 3+, or 4+ if present
      Note: Do not attempt to differentiate types of epithelial cells. If significant numbers of renal tubular epithelial cells are seen, consult a pathologist before reporting the differentiated type.
    4. Bacteria: grade Trace, 1+, 2+, 3+, 4+ if present.
    5. Crystals: Crystals are not usually found in freshly voided urine but appear after the urine stands for a while. Since crystal formation tends to be pH-dependent, it is helpful to be aware of the pH of the urine when performing the microscopic examination. Identify the crystals seen and grade Trace, 1+, 2+, 3+, 4+. Crystals commonly seen include the following:
      1. Ammonium biurate
      2. Amorphous phosphate
      3. Amorphous urate
      4. Bilirubin crystals
      5. Calcium carbonate
      6. Calcium oxalate
      7. Calcium phosphate
      8. Calcium sulfate
      9. Cholesterol
      10. Cystine
      11. Hippuric acid
      12. Leucine
      13. Sodium urate
      14. Triple phosphate
      15. Tyrosine
      16. Unidentified crystals
      17. Uric acid
    6. Casts (# per LPF): Urinary casts are formed in the lumen of the tubules of the kidney. They have nearly parallel sides and rounded or blunted ends and they vary in size and shape according to the tubules in which they are formed. Identification of types of casts is done with high power (450X).
      1. Hyaline Cast: Hyaline casts are the most frequently occurring cast in the urine. They are composed of only protein. They are colorless, homogeneous, transparent and usually have rounded ends.
      2. Red Cell Cast: Red cell casts indicate renal hematuria and are considered pathologic. They may appear brown to almost colorless. The cast may contain only a few RBCs in a protein matrix or there may be many cells packed close together with no visible matrix. If the red cells are intact, then the cast is termed a red cell cast. If the red cells have degenerated to a reddish-brown granular appearance, with no visible intact cellular components, the cast is termed granular.
      3. White Cell Cast: White cell casts are present in renal infection and in noninfectious inflammation. The majority of white cells that appear in casts are polymorphonuclear neutrophils. The WBCs in the cast may be few in number or many cells tightly packed together.
      4. Granular Cast: Granular casts either result from the degeneration of cellular casts or represent the direct aggregation of serum proteins. Finely granular casts contain fine granules, which appear grey or pale yellow in color. Coarsely granular casts contain larger granules that are darker in color and often appear black because of the density of the granules.
      5. Epithelial Cell Cast: Epithelial cell casts form as the result of stasis and the desquamation of renal tubular epithelial cells. The epithelial cells are either arranged in parallel rows in the cast or arranged haphazardly and vary in size, shape and stage of degeneration.
      6. Waxy Cast: Waxy casts have a high refractive index with a smooth homogeneous appearance and are yellow, grey or colorless. They frequently occur as short broad casts with blunt or broken ends and often have cracked or serrated edges.
      7. Fatty Casts: Fatty casts are casts, which have incorporated either free fat droplets or oval fat bodies. If the fat is cholesterol, the droplets will be anisotropic and will demonstrate a characteristic “maltese cross” formation under polarized light. Triglyceride, isotropic droplets, will not polarize but will stain with Sudan III or Oil Red O.
      8. Cylindroids: Cylindroids resemble casts but have one end, which tapers out, like a strand of mucous. Since they usually occur in conjunction with casts, they are considered to have the same significance.
    7. Miscellaneous: Name miscellaneous items and grade Trace, 1+, 2+, 3+, 4+ if present on HPF.
      1. Oval fat bodies
      2. Pinworm ova
      3. Schistosoma haematobium
      4. Trichomonas vaginalis
      5. Yeast
  5. For Acetone, Random Urine test requests: Only the Ketone result is reported. Cross out all other results on the printout. Results must be manually data entered in the LIS.

IX. Expected Result(s) and/or Critical Values:

  1. Gross Examination:
    1. Color: Yellow
    2. Appearance: Clear
  2. Chemical Examination:
    1. pH: 5.0 to 7.5
    2. Protein: negative
    3. Glucose: negative
    4. Ketone: negative
    5. Bilirubin: negative
    6. Blood: negative
    7. Nitrate: negative
    8. Urobilinogen: 0.1 to 1.0 Ehrlich unit/dl
    9. Specific gravity:
      Note: Multistix 10SG package insert normal range is 1.005 to 1.035. 0.005 must be added to SG when pH read visually is ≥ 6.5. This extends the manual reporting range to 1.035.

      Random specimen: 1.005 to 1.035
      24 hour specimen: 1.015 to 1.025
    10. Leukocyte esterase: negative
  3. Microscopic Examination:
    1. RBC: 0-5/hpf
    2. WBC:0-3/hpf

X. Quality Control:

Refer to the “Urinalysis Quality Control” protocol.

XI. References:

  1. “A Handbook of Routine Urinalysis”, 1983, pp 107-116, pp 75-76.
  2. Todd, Sanford, Davidsohn, “Clinical Diagnosis and Management By Laboratory Methods;" 16th Ed., Vol. 1, pp 559-630.
  3. Gradwohl's "Clinical Laboratory Methods and Diagnosis," 8th Ed., Vol. 1, pp.478-503.
  4. Package insert for N-Multistix SG, Miles Inc. Diagnostics Division, Elkhart, IN. 1992.
  5. Haber, Meryl H., Urinary Sediment: A Textbook Atlas. ©1981, ASCP Press.
  6. Slagel, Daniel, M.D.; Pathologist. 1/11/05
  7. Cole-Taylor Urinalysis Reagent Strip package insert. Cole-Taylor Marketing Inc. Van Nuys, CA. 900-10P11.


  1. 6-77 S. Raymond
  2. 10-93 S. Raymond; L. McGovern (Revised: Added reticule note.)
  3. 4-94 L. McGovern (Revised: Changed VII.3.C.b., Deleted VIII.2.C. (sulfosal protein).)
  4. 4-94 L. McGovern (Revised VII.3.C.a-i., XI.4)
  5. 6-94 M. English, L. McGovern (Revised VIII.1.A.c.8.,3.,4.,XI.1.)
  6. 12-94 L. McGovern (Revised VII.3.C.i.Note)
  7. 3-5-99 B. Lucas (Revised: IV.1.-4., V, VIII.3.&4., XI.5)
  8. March 2000 B. Lucas/L. McGovern (Revised: VII.3 & 4.; addition of leukocyte esterase)
  9. June 2000 L. McGovern/S. Raymond (Revised: I., VII.4.)
  10. September 2004 L. McGovern (Revised: updated for Clinitek STATUS)
  11. March 2007 L. McGovern (Revised: Cole-Taylor Urinalysis Reagent Strip)
  12. December 2008 L. McGovern (Revised: for Bayer Multistix 10SG Urinalysis Reagent Strips)
  13. October 2009 L. McGovern (Revised: I.; VII.4.)
  14. March 2011 L. McGovern (Revised: VIII.3.B-C., 4.C-G.)


Comprehensive Review:


Technical Director:


Interim Review:
July 2010 A. Cartmill, L. McGovern (Revised: I.; III.3.; V.1.; VII.2.A., 4.; IX.2.I.note)
April 2011 S. Dunn, M. English (Revised: result “Tr” to “Trace”)
July 2011 R. Tugade (no changes)
April 2012 L. McGovern (Revised: I.; VIII.5.; acetone random urine added)

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