Gerald D. Redwine, PhD, MT(ASCP)

The physical and chemical examination of urine samples plays an essential role in the diagnosis of patients’ pathological conditions. However, the sheer number of routine urinalysis can minimize their significance, especially considering that most analyses are automated, which can foster complacency for less than apparent problems. As a result of seemingly more critical concerns, one may defer the interpretation for the clinician to assess. Nevertheless, detecting abnormal results and possible causes is required, regardless of whether the analysis was manual or automated. Knowing the effects of pigmentation, drugs, pH, and ascorbic acid, for example, are samples that always need attention.

Manual analysis is further complicated, with several idiosyncrasies innate to manufacturers. For example, differences in popular brands, such as, Multistix, that requires reading each chemical pad at the specific time indicated. But the Chemstrip and vChem strips readings are stable between one and two minutes, except leukocytes read at two minutes, all necessitating the need for special attention to the manufacturers’ instructions. Concerning ascorbic acid, knowing that Chemstrip eliminates ascorbic acid interference with blood by overlaying the pad with iodate, and the vChem strips have a detection pad for the substance; in contrast, knowing that the Multistix has neither, is essential. Finally, knowing to ignore the different coloration on the perimeter of the pad on all strips and asking for a recollect on extremely high pH is also vital.

How are the critical thinking skills needed for a urinalysis assessment best developed? In academia, it seemed best, following initial training, to have students complete weeks of daily intensive practice of the entire urinalysis (physical, chemical, and microscopic) in an open lab setting on multiple patient samples. In combination with these analyses, they were given case studies like the ones administered later in a practical examination. The following is a composite of the answer stating what they thought was the most probable cause to three of the 17 cases given on their exam, using Multistix, with further comments in parenthesis. Assessments constrained the students to answer the question under the given condition, knowing they would ask for a recollect in some instances.

Case 1

Physical Examination Observed Result
Color Light yellow and cloudy
Chemical Examination Observed Result
Glucose Neg
Bilirubin Neg
Ketone Moderate
Specific Gravity 1.015
Blood Large
pH 5.0
Protein 30
Urobilinogen 0.2
Nitrite Neg
Leukocytes Moderate
Confirmatory Tests  
Protein (SSA) Trace
Ketones (Acetest®) Pos
Bilirubin (Ictotest®)  

 

  1. What would explain the apparent disagreement between the nitrite and leukocyte reaction?
  2. What accounts for the clarity of the sample in the chemical examination?
  3. What does the Acetest suggest about the chemical reactions, based on literature?

Responses:

  1. Non-nitrate reducing organism. (i.e., bacteria, yeast, trichomonads, and chlamydia) Or Trauma. (Other less likely possibilities.)
  2. Large blood. (Also slightly enhanced the protein.)
  3. More sensitive because of the added glycine. (Glycine detects acetone. vChem strips have the same.)

Case 2

Physical Examination Observed Result
Color Yellow-brown and clear
Chemical Examination Observed Result
Glucose 2000
Bilirubin Small
Ketone Neg
Specific Gravity 1.030
Blood Moderate
pH 8.5
Protein 2000
Urobilinogen 0.2
Nitrite Positive
Leukocytes Negative
Confirmatory Tests  
Protein (SSA) 2+
Ketones (Acetest®)  
Bilirubin (Ictotest®) Small

 

  1. What could explain the single most unexpected finding within the chemical reactions?
  2. What could account for the protein and SSA discrepancy?
  3. What should the adjusted strip value read?
  4. What is the definitive source(s) for reporting the final specific gravity (SG) reading (manual/analyzer/and or name another source) on this specimen?
  5. With an SG = 1.040, what value is the final specific gravity?

Responses:

  1. Negative leukocytes could result from any or all three of the following. 1) Alkalinity 2) >3g/dL glucose 3) High specific gravity.
  2. Alkaline pH can cause a false positive protein; also, the blood that is missing in the supernatant for the SSA could account for the 2+ SSA.
  3. Because pH is ≥ 6.5, then add .005 to the dip strip value. Strip SG = 1.035. (Multistix only)
  4. Because of the ≥ 100 protein, then run on the refractometer. (Total Solid (TS) meter/Refractometer.)
  5. Subtract 0.003 for every 1 g/dl protein; subtract 0.004 for every 1 g/dl glucose. Report SG: 1.026.

Case 3

Physical Examination Observed Result
Color Yellow-green
Chemical Examination Observed Result
Glucose Neg
Bilirubin Neg
Ketone Neg
Specific Gravity 1.010
Blood Trace
pH 8.5
Protein 300
Urobilinogen 0.2
Nitrite Neg
Leukocytes Large
Confirmatory Tests  
Protein (SSA) 1+
Ketones (Acetest®)  
Bilirubin (Ictotest®)  

 

  1. What could explain the disagreement that exists within the chemical reactions?
  2. Explain the correlation between chemical reactions and the SSA?
  3. What are the two specific adjustments needed for the specific gravity?
  4. What is the final strip specific gravity?

Responses:

  1. A non-nitrite reducing microbe such as Trichomonas or Chlamydia. Or postrenal trauma. (Other nitrite negative possibilities. Also, if not for the trace protein, ascorbic acid is suspect.)
    Best observation: Yellow-Green ~ Biliverdin. False-negative bilirubin. Hence, the need for a recollection and run on a fresh sample to ascertain the true values.
  2. Expected the SSA to be greater. Alkaline pH can cause a false positive protein, or in this case, falsely increase the value.
  3. Because pH is ≥ 6.5, then add .005 to the dip strip value. Because of the ≥ 100 protein, then run on the refractometer. TS (Total Solid) meter/Refractometer. (Multistix only)
  4. Strip SG = 1.015.

Responses to the open lab concept, despite significantly more than usual time commitment on behalf of all involved, and reagents, the sacrifices were met with positive feedback from the students on superseding their learning outcomes. The learning outcomes summarized is critical thinking applied to urinalysis case studies.

Reference:
Brunzel, N. A., MS, MLS(ASCP)CM. Fundamentals of Urine and Body Fluid Analysis, 4th Edition

Gerald D. Redwine is an associate professor at Texas State University Clinical Laboratory Science Program in San Marcos, Texas.