Body Fluid Analysis Exam 2

Lipid-soluble pigment in plasma excreted in urine that gives it a yellow color

urochrome

What color is concentrated urine?

dark yellow

What color is dilute urine?

pale yellow

What are the substances that change color in urine?

blood or myoglobin, bilibubin, porphyrins, melanin, indican, homogentisic acid

Ingested substances that change color in urine

medications, dyes, vitamins, pigmented foods

Test for melanoma

Melanin

Tryptophan metabolite

Indican

Alkaptonuria (black urine disease,) is a very rare inherited disorder that prevents the body fully breaking down two amino acids, tyrosine and phenylalanine

Homogentisic acid

Normal urine when shaken will produce what color foam that rapidly dissipates?

white

Stable white foam indicates large amounts of what?

albumin in urine

What is not normally included on report forms?

foam

What is caused by increased bilirubin?

yellow foam

What describes cloudiness of urine caused by suspended particulate matter that scatters light?

clarity

Normal specimens are supposed to be what?

clear

What are the causes of cloudiness?

Contamination from skin or vaginal secretions, bacterial growth, or fecal material, precipitation of dissolved solutes, x-ray contrast media, RBCs, WBCs, epithelial cells, clots, bacteria casts

Normal urine has what?

odor

Urine on standing becomes odorous due to what?

bacterial conversion of urea to ammonia

Ingestion of certain foods or drugs do what?

change odor

What are unusual odors of some metabolic disorders?

Ketones produce sweet or fruity smell, and amino acid disorders often produce odd odors

What refers to the amount of solutes present in volume of water excreted?

concentration

Urine normally consists of what?

94% of water and 6% solutes

Solute types vary with what?

patient's diet, physical activity and health

What has fewer solute particles per volume of urine?

Dilute urine

What is a crude indicator of concentration?

color

What refers to an expression of concentration in terms of density? (Mass of solutes present per volume of solution)

Specific gravity (SG)

What two components affect SG?

# of solute particles and molecular size

The greater the density.....

the greater the SG

What is the lowest possible urine SG?

Is about 1.002 and highest about 1.035-1.040

Methods of measurement can be what?

direct or indirect

Indirect method based on refractive index of light

Refractometry

What happens when light passes from air into a solution at an angl?

it refracts and slows direction of beam

The ratio of light refraction in two differing media is called

refractive index

What happens as number of solutes increase?

Light velocity decreases and light angle decreases

The three factors that affect the refractive index of a solution is?

Wavelength of light used, temperature of solution, and concentration of solution

What does refractometry measure?

all solutes present including protein and glucose

What is the most. common wavelength used?

589 nm

With refractometry a small sample size is what?

1 to 2 drops

Automatic temperature compensations are between what?

15 and 38 degrees C

Indirect colorimetric estimation of urine density based on amount of ionic or charged solutes present (sodium [Na],potassium [K], chloride [Cl], ammonium [NH4]) and is the only method that eliminates effect of nonionic large-molecular weight solutes on specific gravity

Reagent strip method

What happens during the reagent strip method?

Reagent strip pad impregnated with polyelectrolyte and pH indicator at an alkaline pH, when strip immersed in urine, protons released from polyelectrolyte in proportion to ionic concentration, released protons change pH of test pad, resulting in a color change of pad

Concentration of a solution expressed in terms of osmoles of solute particles per kilogram (kg) of water

Osmolality

Often used for convenience due to low osmolality of biological solutions

Milliosmoles

What are normal urine values?

275 to 900 mOsm/kg

What are normal serum values?

275 to 300 mOsm/kg

What are the principal uses of osmolarity?

Evaluate renal concentrating ability of kidneys, Monitor renal disease, Monitor fluid and electrolyte balance, Differentially diagnose cause of polyuria

What is osmolality determined by?

Measuring a colligative property of solution such as freezing point depression or vapor pressure depression

What is able to detect presence of volatile solutes and have accurate results even with lipemic samples?

freezing point osmometry

Pure water freezes at what?

0 degrees C

By adding 1 osmole of solute particles to 1 kg of pure water, what happens?

Decreases freezing point by 1.86 degrees C

The osmometer reads freezing point of sample and converts to a direct readout in what?

milliosmoles

What is not as common as freezing point osmometry but small in sample size and has inability to measure volatile solutes limiting its clinical applicability relative to freezing point depression method?

Vapor pressure osmometry

Vapor pressure osmometry indirectly measures what?

decrease in vapor pressure caused by solutes in a sample by measuring decrease in dew point temperature

What is normal volume?

600 to 1800 mL per day

The amount of solutes excreted increases as water...

required to excrete them increases

Isosthenuria

Inability of kidneys to change specific gravity of plasma ultrafiltrate (which is 1.010)

Polyuria

Excretion of greater than 3 L/day

Oliguria

Excretion of less than 400 mL/day

Anuria

Complete lack of urine excretion

What is the most common method for chemical testing?

Reagent strips

What should strips be protected from?

moisture, heat, chemicals, and light with tight-fitting lids and desiccant in container

Should be stored in original container that is below what?

30 degrees C

Products are susceptible to light, heat, and moisture and should be checked for what?

deterioration before each use

Room conditions for appropriate testing should have what?

good lighting, preferably flourescent, avoid direct sunlight

Urine specimen

at room temperature

What are some reasons to use tablet/liquid tests?

Confirm results obtained by reagent strip testing, alternative method for highly pigmented urine that may make reagent strip result interpretation more difficult, some tests are more sensitive than strip testing, tests specificity differs from strip method

Normal pH varies from what?

4.5 to 8.0, usually slightly acidic but more alkaline after meals

What can pH affect?

stability of formed elements

The principle of pH is based on what?

double indicator system, uses bromothymol blue and methyl red

pH produces a color change from

orange (pH 5.0) to green (pH 7.0) to blue (pH 9.0)

Hematuria

Red blood cells (RBCs) in urine

Hemoglobinuria

Free hemoglobin in urine

What detects hemoglobin heme moiety, so reagent strip also detects myoglobin

Blood

Pad has

chromogen and peroxide

Pseudoperoxidase activity of heme reduces

peroxide, and chromogen is oxidized, causing color change from yellow to green

Ascorbic acid is known to interfere with reaction and can cause a

false-negative reaction

Positive microscopic findings but a

negative reagent strip result

Normally, few white blood cells (WBCs) seen in urine; equivalent to 0 to 8 per high-power field or approximately 10WBCs per microliter

leukocyte esterase

Greater than 20/μL is an indication of

pathologic process

WBCs susceptible to lysis, so may not be seen but will release enzyme causing a

positive reagent strip result

Principle based on action of leukocyte esterase to then

cleave an ester in pad

Cleavage forms an aromatic compound which couples with a

diazonium salt in test pad

End result is azo dye and color change from

beige to violet

Able to detect

10 to 25 WBCs/ul

Nitrate-reducing bacteria in urine can form

nitrate

Nitrate requirements include

Bacteria present must be nitrate reducers, Adequate time in bladder to be reduced (4 hours), Adequate dietary nitrate intake

Principle based on diazotization reaction of nitrite with an aromatic amine in pad which

Forms a diazonium salt, which couples with an aromatic compound in pad to produce azo dye and color change white to pink

What amounts of small-molecular-weight proteins are in urine?

normally very small

Urine protein is often first sign of

kidney damage

Strip test most sensitive to

albumin

Principle based on the protein error of indicators

When buffers in pad hold pH constant, certain indicator dyes release H ions due to proteins present, Hydrogen (H) ions combine with protein, causing a color change, intensity of the color proportional to protein amount

Low levels of albumin

microalbumin

Route strip tests are unable to detect albumin in urine that is

less than 1 to 2 mg/dL

Sensitive albumin tests detect

low-level albuminuria

Variety of test methodologies

Monoclonal antibodies and Chemical reactions with dye binding

What is NOT seen in normal urine?

glucose

Will appear if plasma level in urine is over threshold level of

160 to 180 mg/dL

Principle of glucose is based on a double sequential

enzyme reaction that is specific for glucose

Glucose oxidase in pad oxidizes glucose to form

hydrogen peroxide and gluconic acid

Peroxidase in pad catalyzes formed hydrogen peroxide to oxidize chromogen in pad resulting in a

color change

Test for reducing substances

Clinitest tablets