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Methods/principles of Tests


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What 2 things measure specific gravity?
How does refractometer measure spcf gravity?
Dissolved solids alter refractive index of solution
How does multistix measure spcf gravity?
When ionic conc. is changed, the pKa of a poly-electrolyte changes and indicated by color.
What denotes high or low spcf gravity? values?
Hypersthenuria = 1.025
Hyposthenuria = 1.007
What causes hypersthenuria?

What causes hyposthenuria?
Hyper = diabetes mellitus or x-ray contrast mdia

Hypo = diabetes insipidus
What is isosthenuria?
What causes it?
-Usually 1.010
-Renal tubular damage
What 3 methods detect pH?
-Double indicator system
What 2 compounds are used as pH indicators?
Methyl red
Bromthymol blue
What color is an:
-Acid pH?
Acid = orange

Alkaline = blue
What is urine pH normally?
What is abnormal?
Normal = acid

Abnormal = neutral or alkaline
What is used to measure glucose?
What is the basic reaction principle in the tests?
Double-sequential enzymatic;
1.Glucose oxidase makes peroxide and gluconic acid.
2. peroxidase produces oxidized chromogen.
What chromagen is produced in:
Multistix = K-Iodide
Chemstrip = Terra methyl enzidine
What is the sensitivity in each strip's glucose test?
Multistix = .075 to .125 g/dl
Chemstrip = .04 g/dl
What can cause false reactions in the glucose tests?
Positives: hypochlorite
Negatives: ascorbic acid, 2+ ketones
What are 2 causes of glycosuria?
-Diabetes mellitus
-Renal glycosuria
What test is used to confirm glucose?
What is the principle of the clinitest?

What is its sensitivity?
CuSo4 is reduced to Cu2O

0.25 g/dl
What 8 sugars/acids will make the clinitest positive?
-Glu, lact, fruct, Galactose, pentose.
-Ascorbic acid, homogentisic acid.
What is used to measure ketones?
What is the multistix reaction for ketones?

What is the chemstix rxtn?
-Acetoacetic acid + NA Nitro-
prusside makes a maroon complex.

-Acetoacetic acid + acetone + Na nitroferricyanide + glycine in alkaline pH makes violet complex.
What is the sensitivity of the:
-Multistix rxtn?
-Chemstix rxtn?
Multi = 5-15 mg/dl diacetic

Chemstrips = 9 mg/dl diacetic OR 70 mg/dl acetone.
What ketone bodies are present in ketonuria?
Acetone .02
Acetoacetic acid .2
Beta-hydroxybutyric acid .78
What causes false positives in the ketone reactions?
cpd's containing sulfhydryls
How do the strips detect protein?
By protein error of indicators; buffered pH of 3.0
What is the protein indicator in
Multi = tetrabromphenol blue.
Chem = tetrachlorophenol-tetrabromosulfophthalein.
What is protein sensitivity in:
Multi = 15-30 mg/dl
Chem = 6 mg/dl
What can cause false positives in the protein tests?
-Highly buffered/alkaline urine
What is a limitation of the protein tests?
-Most sensitive to albumin; neg doesn't rule out mucoproteins, globulins, bence-jones.
What test confirms pos protein?
What is the principle of the SSA test?
3% Sulfosal. acid precips protein to make turbidity.
What is the sensitivity of the SSA method?
5-30 mg/dl
What can cause false positive SSA tests?

False neg?
-X-ray contrast media
-Bence jones

Neg: alk urine/highly buffered
What are the 6 causes of proteinuria?
1. Orthostatic
2. Physiologic
3. Glomerular nephritis
4. Nephrotic syndrome
5. Multiple myeloma
6. Renal tubular disorders
What are the rxtns for bili on:
Bilirubin + diazotized di-chloroanaline in acid pH to make purple-tan color.
What are the rxtns for bili on:
Bilirubin + dichlorobenzene- diazoniumtetraflouroborate in acid pH makes tan-pink color
What are the sensitivity for bilirubin on chem vs. multistix?
Multistix: .4-.8 mg/dl
Chemstrips: .5 mg/dl
What can cause false negatives for the bilirubin test?
Ascorbic acid.

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