Reagent Strip Interactions

Albumin + dye —> albumin-dye complex + H+

• causes color progression through green to blue

What interferes with reagent strip reactions?

• highly alkaline urine

• false positives

• false negatives for proteins other than albumin

What is Sulfosalicylic Acid Confirmation (SSA)

• screening or confirmation

• SSA precipitates proteins without heat 

• use centrifuged specimen 

• compare standards 

What are interferences for sulfosalicylic acid confirmation?

• radiographic dye

• antibiotics

What is the clinical significance of glucose?

• diabetes mellitus

• renal threshold: 160-180 mg/dL

• higher blood sugar

  • glycosuria 

What can glucose tests tell us? 

• gestational diabetes

• hormonal disorders

• renal glycosuria 

Glucose oxidase reaction

• specific for glucose 

Glucose + O2 → gluconic acid + H2O2

H2O2 + chromogen → oxidized chromogen + H2O peroxidase

False positive reaction interference in glucose reactions

• peroxide or oxidizing detergents 

False negative reaction interference in glucose reactions

• enzymatic reaction interferences

  • ascorbic acid

  • high ketone levels

  • high specific gravity

  • old specimen

Clinitest Procedural Notes

• not a specific test for glucose 

• copper sulfate reacts with reducing substances to form cuprous oxide 

  • causes color change

• tests for other sugars (galactose)

what are the 3 intermediate products of fat metabolism

• acetone

• acetoacetic acid

• beta-hydroxybytyric acid 

What is produced from acetoacetic acd

• acetone

• beta hydroxybutyric acid 

• both appear in urine when fat is broken down to glucose for energy

What is the clinical significance of ketones in urine

• diabetes melitus 

• vomiting 

• starvation, malabsorption, dieting 

all deal with loss of carbohydrates 

Reagent Strip Reaction for ketones

acetoacetic acid + NA nitroprusside → color change

Reaction Interferences for Ketones

• medication

• abnormal urine color

• only measures acetoacetate

• false positives

  • improper timing

• false negatives

  • old specimens 

Acetest Procedure

• tablet form 

• compare tablet color with color charge

• report negative, small, moderate, or large 

Why is a tablet used in acetest procedure

• provides better color and is more sensitive 

Blood

• reagent strip is more accurate than microscopic for detecting this 

Hematuria due to intact RBc produces red cloudy urine. this can indicate…

• renal calculi

• glomerulonephritis

• pyelonephritis

• tumors 

• trauma

• exposure to toxic chemicals

Hemoglobinuria produces red clear urine. this can indicate…

• transfusion reactions

• hemolyic anemias

• sever burns 

• infection/malaria

• strenuous exercise

• RBC trauma

• brown recluse spider bites 

Hemosiderin produces yellow brown granules in sediment. this can indicate…

• reabsorption of filtered hemoglobin

Myoglobinuria

• heme containing protein within muscle tissue

• produces red/brown, clear urine

Myoglobinuria causes

• muscular trauma

• prolonged coma

• convulsions

• muscular wasting diseases

• alcoholism/overdose

• drug abuse 

• cholesterol lowering statin medication 

Hematuria

• nephritis, trauma 

Hemoglobinuria

• hemolysis 

Myoglobinuria

• rhabdomyolysis

• burns 

Reagent strip reaction for blood

blood+ peroxide lysing agent = hemoglobin

hemoglobin + indicator = color change

What is shown on reagent strip reaction for blood?

• intact RBC in specked pattern

Reaction interference false positive  for blood

• strong oxidizing agents

• bacterial peroxidases

• menstrual contamination 

Reaction interference false negative  for blood

• high specific gravity 

• crenated cells 

• unmixed specimens

• medications 

• ascorbic acid > 25 mg/dl

Bilirubin

• degradation product of hemoglobin

• correlates with urobilinogen and serum bilirubin  

What is the clinical significance of bilirubin

• bile duct obstruction 

  • bilirubin backs up in circulation 

• liver disease

  • bilirubin leaks back into circulation from damaged liver

Reagent Strip reaction for bilirubin

bilirubin + diazo salt → azobilirubin

reaction interference for false positive bilirubin test

• urin pigments

reaction interference for false negative bilirubin test

• old specimen 

• increases ascorbic acid and nitrite

• exposure to light 

Ictotest

• confirmatory for bilirubin

• diazo salt reaction 

Urobilinogen

• bilirubin in intestine converted to urobilinogen and stercobilinogen

• reabsorbed into circulation 

Clinical significance of urobilinogen

• early detection of liver disease

• hemolytic disorders

• bile duct obstruction 

Reagent Strip Reaction for urobilinogen

urobilinogen + ehrlich reagent → colored complex 

Multistix false positive reaction interference for urobilinogen 

• ehrlich reactive compounds

• cold specimens

Chemstrip false negative reaction interference for urobilinogen

• high nitrite interferes 

Clinical significance of nitrite

• gram negative bacteria is most common

• UTI

• cystitis

• pyelonephritis

• evaluation of antibiotic therapy

• monitoring of patents at high risk for UTI

Nitrite reagent strip reaction

nitrite + p-arsenilic acid → diazo compound

diazo compound + tetra robenza quinolinol → colored complex 

• tests ability of bacteria to reduce nitrate to nitrite  

Reaction interference false negative for nitrite reagent strip

• other bacteria

• lack of urinary nitrate

• presence of antibiotics

• high concentration of ascorbic acid

• high specific gravity 

Reaction interference false positive for nitrite reagent strip

• old specimen

• highly pigmented urine

• pink edges or spotting on reagent strip

Leukocyte Esterase

• detection of leukocytes

• not considered a quantitative test

• detects presence of lysed leukocytes

Clinical significance of Leukocyte Esterase

• UTI

• acute inflammation

• renal calculus 

• seen in chlamydia, yeast, interstitial nephritis

Reagent strip reaction for Leukocyte Esterase

esterase + acid ester → acid + active alcohol

active alcohol + diazonium salt → color change 

Reagent strip reaction for Leukocyte Esterase: false positive reaction interference

• strong oxidizing agents

• highly pigmented urine

• menstrual contamination 

Reagent strip reaction for Leukocyte Esterase: false negative reaction interference

• high concentration of protein, glucose, ascorbic acid

• leukocyte crenation from high specific gravity 

Absorbic acid

• vitamin C

• common interference with different urine test 

• oxidizes certain compounds

• low levels = false negatives