3. Chemical Exam Flashcards by Samantha Boyer

QC of reagent test strips happens when?

every 24 hours
new bottle opened
questionable results
concern about integrity

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Why can’t the = control for reagent test strips be DI?

Needs to have a similar ionic concentration to urine.

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confirmatory testing

use of different reagents or methodologies to detec the same subtances with the same or greater sensitivity or specificity

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importance of pH on test srip

determining existence of systemic acid-base disorders
management of urinary conditions that require urine to be monitored at specific pH

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2 major regulators of body pH

lungs
kidneys

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how do the kidneys help regulate pH?

secrete H+ and ammonium ions
reabsorbing bicaronate ions

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typical pH of first morning specimen

normal random sample pH range

5.0-6.0

4.5-8.0
(pH outside this range is physiologically impossible)

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physiological causes of acidic urine (9)

respiratory acidosis (emphysema)
DM
starvation
dehydration
diarrhea (base out the bottom)
acid-producing bacteria
high-protein diet
cranberry juice
medications

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physiological causes of alkaline urine (6)

respiratory alkalosis (hyperventilation)
vomiting
renal tubular acidosis
vegetarian diet
urease-producing bacteria
old specimen

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principle of pH reaction

double indicator system
methyl red + bromthymol blue
yellow—acid; blue—alkaline

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protein is most indicative of…

early renal disease

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normal urine protein

< 10 mg/dL
100 mg/24 hours

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proteinuria indicated at —- mg/dL

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categories of proteinuria causes

prerenal
renal
postrenal

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proteins found in prerenal proteinuria

hemoglobins
myoglobins
acute phase proteins (infection, inflammation)

usually not detected by routine urinalysis, which detect primarily albumin

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Bence Jones proteins are free ——-, and indicates….

monoclonal Ig light chains
multiple myeloma

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method used to dx Bence Jones proteins

serum electrophoresis + immunoelectrophoresis

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2 types of proteinuria of renal origin

glomerular damage
tubular dysfunction

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most serious and most common type of proteinuria

glomerular damage

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tubular dysfuntion leading to proteinuria is caused by less (filtration/reabsorption/secretion) of low MW proteins

reabsorption

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examples of tubular proteinuria

Fanconi’s syndrome
heavy metal poisoning
severe viral infections

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explain microalbuminuria

development of diabetic nephropathy leading to reduced glomerular filtration and eventual renal failure

type 1 and 2 DM

first predicts onset of renal DM complications

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explain orthostatic proteinuria

increased pressure on the renal vein when in the vertical position causes proteinuria that goes away when you lay down

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prinicple of protein reaction

principle of protein error of indicators
reagent pad is at pH 3, and proteins cause release of H+
H+ turn indicator blue-green

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confirmatory test for protein

sulfosalicylic acid precipitation test (SSA)

principle of SSA

- acid will precipitate proteins out of a solution, making the solution **cloudy** - reacts equally with all forms of protein

most frequently performed chemical analysis on urine

glucose

renal threshold for glucose

160-180 mg/dL

2 types of causes of glycosuria

- hyperglycemia-associated - renal-associated

examples of hyperglycemia-associated glycosuria

Diabetes mellitus Pancreatitis Pancreatic Cancer Acromegaly Cushing Syndrome Hyperthyroidism Pheochromocytoma Central nervous system damage Stress Gestational diabetes

examples of renal-associated glycosuria

Fanconi Syndrome Advanced renal disease Osteomalacia Pregnancy

failure to thrive

galactose in urine lack **galactose-1-phosphate uridyl transferase**

principle of glucose reaction

- double sequential enzyme reaction - includes glucose oxidase, peroxidase, chromogen, and buffer - detects only glucose

vitamin C causes false ---- glucose, blood, and bilirubin

negative

confirmatory test for glucose

copper reduction test clinitest benedict's test

clinitest principle

- detects all reducing substances/sugars - sugars reduce copper sulfate to cuprous oxide, colored green/red

pass through phenomenon

clinitest high glucose levels

why don't ketones normally show up in urine?

all the metabolized fat is completely broken down into carbon dioxide and water

3 ketones and percentages

- Beta-hydroxybutyrate (78%) - Acetoacetic Acid (20%) - Acetone (2%)

why does DM lead to ketoacidosis even when blood glucose is high?

without functioning insulin, the body cannot use the glucose that is available

clinical significance of ketonuria

Diabetic acidosis Insulin dosage monitoring Malabsorption/pancreatic disorders Strenuous exercise Vomiting Eating disorders Inborn errors of amino acid metabolism

principle of ketone reaction

- at an alkaline pH, acetoacetate reacts with **sodium nitroprusside** to produce a **purple** color - only detects acetoacetic acid unless **glycine** is included, and then detects acetone also

confirmatory test for ketones

acetest

acetest principle

- tablet includes sodium nitroprusside and glycine - turns purple with ketones

Reabsorption of filtered hemoglobin also results in the appearance of large yellow-brown granules of denatured ----- called ------ in the renal tubular epithelial cells and in the urine sediment.

ferritin hemosiderin

brown recluse spider bites

hemoglobinuria

muscle destruction

rhabdomyolysis

statin medications

rhabdo myoglobinuria

blood reaction principle

- **pseudoperoxidase** activity of hemoglobin to oxidize chromogen - **green-blue** color - reacts with RBCs, hemoglobin and myoglobin

------ cells can give false negative blood

crenated

2 types of bilirubin

- **unconjugated**/indirect: water insoluble, bound to albumin in blood stream - NOT in urine - **conjugated**/direct: water soluble, can be found in urine

In the liver, bilirubin is conjugated with -------- by ----------- to form -------------, commonly called conjugated bilirubin.

glucuronic acid glucuronyl transferase bilirubin diglucuronide

Bacteria in the intestines reduces the conjugated bilirubin to ----------- and -------------.

urobilinogen stercobilinogen

----bilinogen can be reabsorbed or excreted in urine, and ----bilinogen cannot be reabsorbed and remain in intestine

urobilinogen stercobilinogen

give stool its color

urobilin and stercobilin

clinical significance of bilirubinuria

Hepatitis Cirrhosis Other liver disorders Biliary obstruction (gallstones, carcinoma)

bilirubin reaction principle

- **diazo** reaction - conjugated bilirubin combines with diazonium salt to form **azodyte**

confirmatory test for bilirubin

ictotest

ictotest for bilirubin

----% of urobilinogen is reabsorbed

2-5%

urobilinogen is quickly converted to ------ on standing

urobilin

peak levels of urobilinogen

2-4 PM

normal urobilinogen

< 1 mg/dL

clinical significance of urobilinogen

Early detection of liver disease Liver disorders, hepatitis, cirrhosis, carcinoma Hemolytic disorders Constipation

urobilinogen reaction principle

1. MULTISTIX - **Ehrlich's** aldehyde reaction - **pink** 2. CHEMSTRIP - **diazo** reaction - **red**

limitation of urobilinogen test

cannot determine absence of urobilinogen

preservative that interferes with urobilinogen

formalin

# Pre-Hepatic unconjugated bilirubin conjugated bilirubin urine bilirubin urine UBG fecal UBG

unconjugated bilirubin ↑ conjugated bilirubin normal urine bilirubin = urine UBG ↑ fecal UBG ↑

# Post-Hepatic unconjugated bilirubin conjugated bilirubin urine bilirubin urine UBG fecal UBG

unconjugated bilirubin normal conjugated bilirubin ↑ urine bilirubin + urine UBG = fecal UBG =, white color

why is the nitrite test important?

detecting initial bladder infection, because patients are often asymptomatic or have vague symptoms

nitrite reaction principle

- **Greiss** reaction - nitrite + aromatic amine --> diazonium salt - diazonium salt + tetrahydrobenzoquinolin --> **pink** azo dye

how to provide sufficient contact time for nitrite test

take first morning specimen

lack leukocyte esterase

lymphocytes

LE reaction principle

- acid ester + LE --> indoxyl aromatic compound - aromatic compound + diazonium salt --> **purple** azo dye

trace amounts of LE are insignificant in ------

women vaginal contamination

LE false positives with esterases found in...

histiocytes trichomonas

helps us determine unsatisfactory specimens

↑ SG = --- pH change ↓SG = ---- pH change

↓ pH ↑pH

reagent strip SG only detects...

ionic solutes

principle metabolite of ascorbic acid

oxalate

ascorbic acid is a strong ----- because of its ene-diol group

reducing substance (H+ donator)

reagent tests that use --------- or ------- are subject to vitamin C interference

H2O2 diazonium salt

4 test interfered with by vitamin C

- blood (H2O2) - bilirubin (diazonium) - nitrite (diazonium) - glucose (H2O2)

ascorbic acid reaction principle

- action of ascorbic acid to reduce a dye - blue to **orange**