Chemical Examination of Urine (Principles and Specific Gravity) Flashcards
What reagent strip parameters require 60 seconds before reading?
Protein, pH, Blood, Urobilinogen, Nitrite
What reagent strip parameters are read at 30 seconds?
Glucose and Bilirubin
After how many seconds are ketones read in reagent strips?
40 seconds
How long should you wait to read specific gravity in reagent strips?
45 seconds
What is the time for reading leukocytes in reagent strips?
120 seconds
What is the principle for glucose detection in reagent strips?
Double sequential enzyme reaction
What is the principle of bilirubin detection in reagent strips?
Diazo reaction
What is the principle for ketones detection in reagent strips?
Sodium nitroprusside reaction
What principle is used for specific gravity in reagent strips?
pKa change of a polyelectrolyte
What is the principle for protein detection in reagent strips?
Protein error of indicators
How does the protein strip change its reaction?
When albumin binds to a dye, it releases hydrogen ions (H+) and changes the pH, causing the dye to change color.
What is the principle of pH detection in urine strips?
Double indicator system
What is the principle of blood detection in urine strips?
Pseudoperoxidase activity of hemoglobin
What is the principle of urobilinogen detection in reagent strips?
Erlich reaction
What is the principle for nitrite detection in urine reagent strips?
Greiss reaction
What is the principle of leukocyte detection in reagent strips?
Leukocyte esterase
What is the positive color for glucose in reagent strips?
Green to brown (KI chromogen - potassium iodide)
What is the positive color for bilirubin in reagent strips?
Tan or pink to violet
What is the positive reaction color for ketones in reagent strips?
Purple
What is the color change for specific gravity in reagent strips?
Blue (1.000) to yellow (1.030)
What is the positive color for protein in reagent strips?
Blue green
What is the color change for pH in reagent strips?
Orange (pH 5.0) to blue (pH 9.0)
What color change is observed for blood in reagent strips?
Uniform green/blue (myoglobin/hemoglobin), speckled/spotted (intact RBCs)
What is the positive color for urobilinogen in reagent strips?
Red
What is the positive color for nitrite in reagent strips?
Uniform pink
What is the positive color for leukocytes in reagent strips?
Purple
What happens if the reagent strip technique is prolonged for more than 1 second?
Leach/fading
How should excess urine be removed from a reagent strip?
Touching the edge of the strip to the container as it is withdrawn
How should the urine reagent strip be blotted?
Blot the edge on a disposable absorbent pad
How should reagent strips be held to compare color reactions?
Horizontally
How should reagent strips be stored?
Store with desiccant in an opaque, tightly closed container, below 30°C, and use within 6 months once opened
What is the principle of automated reagent strips?
Reflectance photometry
What happens to light reflection from the test pads in automated reagent strips?
It decreases in proportion to the intensity of color produced by the concentration of the test substance
What happens if the color of the reagent pad is darker in automated reagent strips?
It reflects less light
What is measured to determine the amount of dissolved substances in a solution?
Specific gravity
What influences specific gravity?
Number and size of particles in a solution
What is the reference range for specific gravity in random urine?
1.003 to 1.035
What is the reference range for specific gravity in first morning urine?
> 1.020
What is the reference range for specific gravity in 24-hour urine?
1.016 to 1.022
What does a specific gravity of <1.003 indicate?
Not urine, except in Diabetes Insipidus (1.001)
What is the specific gravity of water?
1
What does a specific gravity of >1.040 indicate?
Radiographic dye is present (if refractometer is used)
What does a specific gravity of 1.010 indicate?
Isothenuria
What is the specific gravity of hyposthenuria?
<1.010
What is the specific gravity of hypersthenuria?
> 1.010
What is the glomerular filtration rate specific gravity?
1.01
What is the calibration temperature for a urinometer/hydrometer?
20°C
What is the temperature correction for a urinometer for every 3°C below the calibration temperature?
-0.001
What is the temperature correction for a urinometer for every 3°C above the calibration temperature?
0.001
What is the correction for glucose in a hydrometer/urinometer for 1 g/dL?
-0.004
What is the correction for protein in a hydrometer/urinometer for 1 g/dL?
-0.003
What is the required urine volume for a urinometer?
10-15 mL
What is the calibration solution for a urinometer?
Potassium sulfate (K2SO4) solution (20.29 g K2SO3 to 1L H2O)
What is the specific gravity reading used to calibrate a urinometer?
1.015
When using a urinometer
how should urine be poured into the container?
Where should the scale reading be taken on a urinometer?
At the bottom of the urine meniscus
What are the steps in using a refractometer?
1) Put 1 or 2 drops of sample on the prism, 2) Close the daylight plate gently, 3) Sample must spread all over the prism surface, 4) Look at the scale through the eyepiece, 5) Read scale where the boundary line intercepts it, 6) Wipe the sample from the prism clean with tissue and water
What is the indirect method formula based on refractive index (RI)?
RI = Light velocity in air / Light velocity in solution
What is the temperature range for refractometry compensation?
15-38°C
Does refractometry require temperature correction?
No, but it needs correction for glucose and protein
What is the calibration refractometry value for distilled/deionized water?
1
What is the calibration refractometry value for 3% NaCl?
1.015 +/- 0.001
What is the calibration refractometry value for 5% NaCl?
1.022 +/- 0.001
What is the calibration refractometry value for 7% NaCl?
1.035 +/- 0.001
What is the calibration refractometry value for 9% sucrose?
1.034 +/- 0.001
What requires correction for glucose and protein in both refractometer and urinometer?
Refractometer and urinometer
How much lower is the refractometer reading than the urinometer reading?
0.002 (Refractometer is lower by 0.002)
What is the specific gravity dilution formula?
Decimal portion x dilution factor
What is the obsolete method for specific gravity (S.G) measurement based on the frequency of sound waves changing in proportion to solution density?
Harmonic Oscillation Densitometry
What is an example of Harmonic Oscillation Densitometry?
Yellow IRIS (International Remote Imaging System)
What is the required urine volume for IRIS diagnostics?
6 mL
What is the required urine volume for the IRIS slideless microscope?
4 mL
What is the required urine volume for the IRIS mass gravity meter?
2 mL