Urine Hemoglobin

Sample for Urine Hemoglobin

1. It can be done with fresh, random urine.
2. A morning sample is preferred.
3. Examine immediately.
4. If examined later on say for one hour then refrigerate the urine in the fridge to avoid microbial growth.
5. Mix urine well before testing the urine for Hb.

Indications for Urine Hemoglobin

1. To find the cause of hemoglobinuria due to various conditions:
   1. Hemolytic anemia.
   2. Other conditions are given below.

Precautions for Urine Hemoglobin

1. Examine immediately.
2. Can refrigerate if delayed.
3. Mix well before testing.

Definition of urine hemoglobin (hemoglobinuria):

1. This is the presence of free hemoglobin in the urine, called hemoglobinuria.
2. When the level of free hemoglobin in the blood exceeds the renal excretion threshold, it results in hemoglobinuria.
3. This lysis of the RBCs takes place in dilute, alkaline urine.
4. The lysis of the RBCs in the urine usually shows a mixture of hemoglobinuria and hematuria.
5. Urine in hemoglobinuria and myoglobinuria is dark red or brown.

Mechanism of hemoglobinuria:

1. Erythrocytes lysis occurs at specific gravity <1.010.
2. This may occur as a result of lysis of RBCs in the urinary tract.
3. Intravascular hemolysis leads to hemoglobinuria. In such cases, no RBCs are seen.
4. This will occur when the reticuloendothelial system can not handle or metabolize the hemoglobin by the hemolysis of RBCs (intravascular).
5. Under normal conditions, there is a complex of haptoglobin-hemoglobin, which will not be filtered by the glomeruli.
6. When the hemoglobin exceeds the amount of haptoglobin in:
   1. Hemolytic anemias.
   2. Severe burns.
   3. Blood transfusion reactions.
   4. Strenuous exercise.
   5. Infections
7. The free hemoglobin can pass through the glomeruli.
8. The excess is absorbed in the proximal convoluted tubules.
9. The free hemoglobin can filter out and appears in the urine as hemoglobinuria.

10. This may also take place by the hemolysis in the urinary tract system.

Hematuria definition: When RBCs are present in the urine, the condition is called Hematuria.

Myoglobinuria definition: The presence of myoglobin is called myoglobinuria. This is due to myoglobin, a muscle protein.

Ammonium sulfate test to differentiate hemoglobinuria and myoglobinuria:

Detection of hemoglobinuria:

1. The small amount of hemoglobin in urine does not give visible color, which can be detected by the dipstick method.
2. O-toluidine gives a blue color to hemoglobin.
   1. This also detects myoglobin.
   2. The false-positive test is seen in the following:
      1. If the container contains hypochlorite, an oxidizing agent.
   3. The false-negative test is seen in the following:
      1. Vitamin C (ascorbic acid).
      2. Formaldehyde.
      3. Sensitivity is low when there are high specific gravity and a high concentration of nitrite.
3. Benzidine test is not used because this is a carcinogenic agent.

• In case of positive urine for occult blood but no RBCs are seen under the microscope, suspect myoglobinuria.

1. This occurs as a result of muscle injury, muscle disease disorder, and some poisoning.

This test detects:

1. RBCs.
2. Hemoglobin.
3. Myoglobin.

Blood in the urine indicates damage to the kidneys or the urinary tract.

The normal value of urine hemoglobin

Source 1

• Normally Hemoglobin is negative in the urine.
• <0.03 mg free Hb/dL.

Causes of Hemoglobinuria:

1. It is positive for all causes of hematuria e.g
   1. Renal calculi.
   2. Tumors.
   3. Exposure to toxic drugs.
2. Intravascular hemolysis.
   1. Pregnancy and in puerpera.
   2. Transfusion reaction.
   3. Kidney infarction.
   4. Extensive burns.
   5. Paroxysmal nocturnal hemoglobinuria.
   6. Drugs and poison, e.g., sulfonamides, quinine, phenylhydrazine, poisonous snake, and fava beans.
   7. Infections, e.g., malaria, blackwater fever, gas gangrene, yellow fever, and anthrax.
   8. Direct trauma to RBC like exercise, heart valve prosthesis.
   9. Microangiopathic hemolytic anemia.
   10. Disseminated intravascular coagulopathy.
   11. Hemolysis in the donor blood due to improper storage.

Urine differentiation between the presence of RBCs, Hemoglobin, and Myoglobin:

Questions and answers: