Methods/principles of Tests
Terms
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- What 2 things measure specific gravity?
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-Refractometer
-Multistix - 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?
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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?
-
-Multistix
-Chemistrip
-Double indicator system - What 2 compounds are used as pH indicators?
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Methyl red
Bromthymol blue -
What color is an:
-Acid pH?
-Alkaline? -
Acid = orange
Alkaline = blue -
What is urine pH normally?
What is abnormal? -
Normal = acid
Abnormal = neutral or alkaline - What is used to measure glucose?
-
-multistix
-chemistrips - 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
-Chemstrip -
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?
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Positives: hypochlorite
Negatives: ascorbic acid, 2+ ketones - What are 2 causes of glycosuria?
-
-Diabetes mellitus
-Renal glycosuria - What test is used to confirm glucose?
- Clinitest
-
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?
-
-Multistix
-Chemstrips -
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?
-
L-dopa
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
-Multistix
-Chemstrips -
Multi = tetrabromphenol blue.
Chem = tetrachlorophenol-tetrabromosulfophthalein. -
What is protein sensitivity in:
-Multistix
-Chemstrips -
Multi = 15-30 mg/dl
Chem = 6 mg/dl - What can cause false positives in the protein tests?
-
-Highly buffered/alkaline urine
-Chlorohexidine. - 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?
- SSA
- 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
-Drugs
-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:
-Multistix - Bilirubin + diazotized di-chloroanaline in acid pH to make purple-tan color.
-
What are the rxtns for bili on:
-Chemstrips - 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.