Chemical Examination Flashcards
What are some of the medically significant tests reagent strips perform? (10)
- pH
- protein
- glucose
- ketones
- blood
- bilirubin
- urobilinogen
- nitrite
- leukocytes
- Specific gravity
Two major type of reagent strips are manufactured under the trade names?
- Multistix
- Chemstrip
Describe Improper Technique Errors with reagent strips? (5)
- Unmixed specimen: form elements like RBCs & WBCs sink to bottom, not moxed remain undetected
- Refridgerated samples must return to room temp; enzymatic reactions temp. dependent on strips.
- Excess urine remaining on strip after removal can cause chemical run over between pads and distort colors.
- Not following manufacturers stated timing. (Leukocyte eserase reaction is 2 mins (120s))
How are reagent strips stored and protected? (4)
- Opaque container (light)
- stored at room temp (<30 degrees)
- Not touch chemical pads when removing strips
- visually inspect each time for detoriation.
Quality control of reagent strips: When are reagent strips checked? (4)
- with positive and negative controls every 24 hrs
- beginning of each shift in labs
- New bottle opened
- questionable results
- strip integrtity concern
Why is distilled water not recommended as a negative control?
Because strip chemical reations are desined to perform at ionic concentrations similar to urine.
Basically it will react with water
T/F all negative controls must be negative and all positive controls must agree with published value +/- 1 color block.
Give an example of reagent strip interference?
- orange pigment in urine caused by medication phenazopyridine masks color reactions.
What is secondary testing?
Test using different reagents / methods to detect same substances by reagent strip with similar or greater sensitivity and specificity.
What is the secondary test for protein?
Sulfosalycylic Acid (SSA)
What is the secondary test for Galactose, Glucose?
Clintest
What is the secondary test for ketones?
Acetest
This is the secondary test and primary confirmatory test for Bilirubin?
Ictotest
What is the pH of the first morning specimen? When is it alkaline?
- slightly acidic 5.0 - 6.0
- more alkaline (alkaline tide) after meals
What is the pH range of normal random samples?
4.5 - 8.0
No normal values are assigned to urine pH, what other patient information must be considered in conjuction with pH?
- acid-base content of blood
- renal funtion
- prescence of a UTI
- dietary intake
- age of specimen
Above what pH is considered improperly preserved?
8.5
Persons with high protein and high meat diets tend to produce what urine pH?
and vegetarians?
What is an exception to the above?
- Acidic
- Alkaline
- cranberry juice - home remedy to treat UTI as it inhibits colonization of some urinary pathogens.
Maintaining acidic urine can be vaulable in treating?
UTI
Reagent strip reactions
- Methly red produces what color change at what pH?
- Bromothymol blue produces what color change at what pH?
- red to yellow at 4 - 6 pH
- green to blue at 5 - 9 pH
How much protein is in normal urine?
<10 mg/dL or 100 mg per 24hrs excreted
Uromodulin also known as what is produced where?
Tamm-Horsfall protien is produced in the distal convoluted tubule
Proteinuria is a common early indicator of what?
Clinical protienuria is indicated at? (#)
- early renal disease
- 30 mg/dL or 300 mg per 24hrs
What are the three major categories of protienuria?
- prerenal
- renal
- postrenal
What causes prerenal proteinuria?
- conditions affecting plasma before it reaches the kidney, not indicative of renal disease.
- usually transient condition
- caused by increases in lmw plasma proteins like Hgb and acute phase reactants associated with infection and inflammation.
- this in NOT discovered in routine urinalysis
A primiary example of protienuria is?
Bence Jones Protein due to multiple myloma.
How is BJP tested?
- Boil Piss
- BJP coagulates between 40 - 60 oC
- dissolves at 100oC
Protienuria associated with true renal disease may be the result of? (3)
- glomerular damage
- tubular damage
- diabetic nephropathy
What are two major causes of proteinuria due to glomerular damage?
- erythmatosus
- streptococcal glomerularnephritis
Protienuria in the latter months of pregnancy may indicate?
pre-eclampsia
Microabumminuria is an early preductor of renal complications and common in people with? and also indicative of?
type 2 and type 2 diabetes mellitus and is also indicative of carsiovascular disease.
What is a benign proteinuria that occurs in young adults?
Orthostatic proteinuria occurs when too much time spent in verticle position
Causes of postrenal protienuria? (3)
- protein can be added to urine as it passes through lower urinary tract structures (bladder, ureters, urethra, prostate, vag)
- bacterial and fungal infectiond produce exudates contaning protein
- Blood from injury or mentral contamination or prostatic fluis and large amounts of spermatozoa
reagent strip (multistix) test for protein contains tetrabromophenol blue color turns from yellow to blue.
reagent strip (multistix) test for protein
causes of interference?
- alkaline urine ovveriding acis-buffer system cause unrelated color change
- false positive if not done under acidic conditions
- highly pigmented urine, ammonium compunds, detergents and antiseptics cause false positives
- false positive with high specific gravity
What is the Sulfosalycylic Acid (SSA) Test?
A cold precipitation test that reacts with all forms of protein.
What is the clinical significance of an SSA test?
Renal Diseases
What is the most frequently performed checmical analysis on urine?
Glucose Test
What is the level at which tubular reabsorbtion of glucose stops?
160 - 180 mg/dL
The glucose oxidase test is specific to glucose.
What is the first and second step of this reaction?
- glucose oxidase catalyses reaction between glucose + air ==> gluconic acid
- perosidase catalyses reaction between peroxise+chromogen ===> oxidized color compound proportional to glucose concentration.
Interfering substance: glucose oxidase test
- False +ve - peroxide and strong oxidizing agents
- False -ve - Enzyme reaction interference - asorbic acid
- High ketones at low glucose concentrations affect test
- High specific gravity can reduce sensitivity
What is the Copper reduction method (Clinitest)?
What do clinitest tablets contain?
What is the color change? and what is ‘pass through’
- glucouse reduce copper sulphate to cuprous oxide in the prescence of alkali and heat.
- copper sulphate, sodium carbonate, sodium citrate, and sodium hydroxide
- Orange/brown
- color change to orange brown and back to green-brown, if not observed can be reported as negative
What can interfere with Clinitest?
- other reducing sugars - galactose, fructose, lactose, pentose etc.
- drug metabolites
- antibiotics
What is the clinical significance of clinitest?
- inborn error of metabolism in neborns
- Diabetes mellitus
Ketones represent what intermediates of fat products?
- acetone 2%
- acetoacetic acid 20%
- beta-hydroxybutyrate 78%
Clinical significance of Keytones in urine?
- Diabetes mellitus
- inability to metabolize carbs
- carb loss from vomiting
- inadequate carb intake
- malabsorbtion
Reagent strip: Ketones
What is the reaction and color change?
Acetoacetic acid + sodium nitroprusside ===> purple color change
What is the clinical significance of hematuria (RBC in pee)?
- renal or genitourinary bleeding
- renal calculi
- glomerula diseases
- trauma
- pyelonephritis
- toxic chemicals
- anticoag therapy
What is the clinical significance of hemoglobinuria (Hgb in pee)? (7)
- lysis of RBCs in urianary tract from alkaline pee
- intravascular hemolysis
- hemolytic anemias
- severe burns
- brown recluse spider bites
- infections
- strenuous exercise
What is the clinical significance of myeoglobinuria (RBC in pee)?
- muscle destruction (rhabdomyolysis)
- high conc of myeglobin toxic to renal tubules and can cause acute renal failure
Appearance of bilirubin in urine is an early indicator of?
What type of bilirubin can appear in urine?
- liver disease
- conjugated bilirubin causing bilirubinuria due to hepatitis / cirrhosis
Reagent strip reaction for bilirubin?
color change?
- Diazo ===> azodye
- pink to voilet
What is the confirmatory test for bilirubin?
Ictotest
reagent strip reaction for urobilniogen?
- Erlich reaction (multistix)
- Normal 0.2 - 1.0 EU
- Abnormal 2. 4. 8 EU
- Diazo reaction(Chemstrip)
- more specific than erlich reaction
Nitrite tests indicate?
UTI
Clinical significance of Nitrite? (3)
- Initial bladder infection (cystitis)
- Pyelonephritis
- evaluate success of antibiotic therapy
Nitrite is detected by what reaction?
Greiss reaction, nitrite at acidic pH reacts w/ aromatic amine to make diazonium compund ====> pink azodye
