What physical and chemical tests can you use, and what data do they provide in the analysis of urine?

Procedure

Consider this scenario. A theft was committed in the washroom of a community building. Forensic specialists collected a urine sample at the scene of the crime. The police have four suspects in custody. Your task is to find out who committed the crime.

You will start by interpreting the results of each test. Record data in the table in the lab document as you go through each test.

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Test 1—Colour, Odour, Clarity: Normal urine is a clear, straw-coloured liquid. Urine may be cloudy because it contains red or white blood cells, bacteria, or pus from a bladder or kidney infection. Normal urine has a slight odour. Foul-smelling urine is a common symptom of a urinary tract infection. A fruity odour is associated with diabetes mellitus.

Control: Urine is yellow. Smell is normal. Looks cloudy.

Crime suspect: Urine is yellow. Smell is fruity. Looks clear.

Suspect 1: Urine is yellow. Smell is fruity. Looks clear.

Suspect 2: Urine is yellow. Smell is normal. Looks clear.

Suspect 3: Urine is yellow. Smell is normal. Looks cloudy.

Suspect 4: Urine is yellow. Smell is fruity. Looks clear.

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Test 2—Protein: One sign of kidney damage is the presence of protein in urine. To test for protein, a portion of each sample is placed in a hot water bath. If the sample becomes cloudy or is cloudier than the original sample, it contains protein.

After a few minutes, the test tube from the hot water bath is removed and compared to the original sample.

If the heated sample is cloudier, it contains protein. The test is positive.

Use the following descriptions of the urine samples to fill in your chart

Control: positive

Crime Suspect: negative

Suspect 1: negative

Suspect 2: negative

Suspect 3: positive

Suspect 4: negative

Test 3—pH: The wide range of pH values (pH 4.7 to 8.5) makes this the least useful parameter for a diagnosis of kidney disorders. Kidney stones are less likely to form and some antibiotics are more effective in alkaline urine. There may be times when acidic urine may help prevent some kinds of kidney stones. Bacterial infections also increase alkalinity, producing a urine pH in the higher 7-8 range.

A clean medicine dropper is used to place a drop of each sample of urine on small pieces of universal indicator (pH) paper. They are left for about 30 seconds. The pH paper can turn several different shades, depending on pH. pH can be determined by comparing the indicator to a colour chart.

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Use the following descriptions of the urine samples to fill in the chart. To determine pH, use this indicator colour chart.

Control: yellow green

Crime Suspect: yellow/green

Suspect 1: orange

Suspect 2: green/blue

Suspect 3: green

Suspect 4: yellow/green

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Test 4—Glucose: One sign that a person has diabetes mellitus is the presence of glucose in the urine.

To test for glucose, a glucose test strip is dipped into each sample of unheated urine and immediately taken out.

The strip is compared to a colour chart. The chart shows a colour gradient from light blue to dark brown. Intermediate colours are greens and browns. Blue indicates no sugar, while dark brown indicates high glucose levels. Intermediate colours indicate the presence of glucose in varying concentrations.

Use the following descriptions of the urine samples to fill in your chart

Control: dark brown

Crime Suspect: dark brown

Suspect 1: light blue

Suspect 2: green

Suspect 3: light blue

Suspect 4: dark brown

From the results of the urine analysis, you should be able to tell which suspect committed the crime, or at the very least left his or her urine at the crime scene.

MODULE 8 LESSON 9 LAB

Lab: Urinalysis

Urinalysis is the physical, chemical, and sometimes microscopic examination of urine. Many diseases with no obvious symptoms can be revealed during urinalysis. Historically, appearance, odour, and even taste have been used to make inferences about a person's health. In this investigation you will interpret urinalysis results from four different tests. You will record your results from the urine analysis outlined

Test Control Tests Crime Scene Suspect 1 Suspect 2 Suspect 3 Suspect 4

Colour

/Odour/Clarity

Protein

pH

Glucose

Analysis:

1.

Who is the thief? Explain how you arrived at your conclusion.

                     Answer:

2.

Based on your urinalysis, identify the disease that Suspect 4 might have. Explain.

                     Answer:

3.

List at least three other characteristics of urine that you would expect to observe (or not) in a healthy urine sample.

                     Answer:

4.

In what ways were the data that you collected in this urinalysis limited? What additional data would provide a more comprehensive picture of a urine sample?

                     Answer:

5.

Explain why you would not expect to find evidence of glucose or protein in a urine sample from someone whose kidneys are healthy. (Use details of nephron anatomy in your answer.)

                     Answer:

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