4.6 BLOOD Flashcards
The presence of intact red blood cells (RBCs) in the urine.
hematuria
The presence of hemoglobin in the urine due to RBC destruction.
hemoglobinuria
How does hematuria differ in appearance from hemoglobinuria in urine?
Hematuria produces cloudy red urine, while hemoglobinuria produces clear red urine.
What are the common causes of hematuria
Renal calculi,
glomerulonephritis,
pyelonephritis,
tumors,
trauma,
exposure to toxic chemicals,
anticoagulants, and
strenuous exercise.
What causes hemoglobinuria to occur?
Intravascular hemolysis,
lysis of RBCs in the urinary tract,
and conditions like
hemolytic anemias,
transfusion reactions,
severe burns, and
infections
is the presence of myoglobin in urine, often caused by muscular trauma, crush injuries, prolonged coma, convulsions, muscle-wasting diseases, or statin use.
Myoglobinuria
Which reagent strip reaction is used to detect blood in urine?
pseudoperoxidase activity
The pseudoperoxidase activity of hemoglobin and myoglobin catalyzes a reaction with what compound in the reagent strip
tetramethylbenzidine
to produce a green-blue color
What clinical conditions are associated with myoglobinuria?
Rhabdomyolysis, trauma, drug abuse, extensive exertion, and statin-induced muscle damage
What are possible causes of false positives for blood in urine
Strong oxidizing agents,
bacterial peroxidases, and
menstrual contamination
What are possible causes of false negatives for blood in urine
High specific gravity,
crenated cells,
formalin,
captopril,
high nitrite levels, and
ascorbic acid
How do reagent strip tests distinguish between hematuria and hemoglobinuria?
Hematuria shows a speckled pattern due to lysed RBCs, while hemoglobinuria shows a uniform green-blue color.
What is the sensitivity of Multistix and Chemstrip for detecting blood in urine?
Multistix: 5–20 RBCs/mL or 0.015–0.062 mg/dL hemoglobin.
Chemstrip: 5 RBCs/mL, hemoglobin corresponding to 10 RBCs/mL.
How does high specific gravity affect the detection of blood in urine?
It can crenate RBCs, preventing them from lysing and leading to false-negative results.
What historical method was used to differentiate between hemoglobinuria and myoglobinuria?
Ammonium sulfate precipitation, where hemoglobin precipitates and myoglobin remains in the supernatant.
Why must urine specimens be mixed before testing for blood?
RBCs can settle to the bottom, leading to falsely decreased readings if the specimen is not mixed.
How does rhabdomyolysis contribute to acute renal failure?
The heme portion of myoglobin is toxic to renal tubules, and high concentrations can cause kidney damage.
is denatured ferritin found in renal tubular cells and urine sediment during hemoglobin reabsorption.
Hemosiderin
What specific medication-related side effect can lead to myoglobinuria?
Statin-induced rhabdomyolysis
How do reagent strips address the interference of ascorbic acid in blood detection?
Multistix uses a less reducible peroxide, and Chemstrip overlays the pad with iodate to oxidize ascorbic acid.
Identify the condition that results from the presence of intact red blood cells (RBCs) in urine.
Hematuria
Identify the substance that produces a clear red urine due to its presence when RBCs are destroyed.
Hemoglobin (hemoglobinuria
Identify the clinical significance of a positive reagent strip test for blood.
The presence of RBCs, hemoglobin, or myoglobin.
Identify the major causes of hematuria related to renal or genitourinary disorders.
Renal calculi, glomerular diseases, tumors, trauma, pyelonephritis, exposure to toxic chemicals, and anticoagulant therapy
