Urine Hemoglobin (Hemoglobinuria)
Sample for Urine Hemoglobin
- It can be done with fresh, random urine.
- A morning sample is preferred.
- Examine immediately.
- If examined later on say for one hour then refrigerate the urine in the fridge to avoid microbial growth.
- Mix urine well before testing the urine for Hb.
Indications for Urine Hemoglobin
- To find the cause of hemoglobinuria due to various conditions:
- Hemolytic anemia.
- Other conditions are given below.
Precautions for Urine Hemoglobin
- Examine immediately.
- Can refrigerate if delayed.
- Mix well before testing.
Definition of urine hemoglobin (hemoglobinuria):
- This is the presence of free hemoglobin in the urine, called hemoglobinuria.
- When the level of free hemoglobin in the blood exceeds the renal excretion threshold, it results in hemoglobinuria.
- This lysis of the RBCs takes place in dilute, alkaline urine.
- The lysis of the RBCs in the urine usually shows a mixture of hemoglobinuria and hematuria.
- Urine in hemoglobinuria and myoglobinuria is dark red or brown.
Mechanism of hemoglobinuria:
- Erythrocytes lysis occurs at specific gravity <1.010.
- This may occur as a result of lysis of RBCs in the urinary tract.
- Intravascular hemolysis leads to hemoglobinuria. In such cases, no RBCs are seen.
- This will occur when the reticuloendothelial system can not handle or metabolize the hemoglobin by the hemolysis of RBCs (intravascular).
- Under normal conditions, there is a complex of haptoglobin-hemoglobin, which will not be filtered by the glomeruli.
- When the hemoglobin exceeds the amount of haptoglobin in:
- Hemolytic anemias.
- Severe burns.
- Blood transfusion reactions.
- Strenuous exercise.
- The free hemoglobin can pass through the glomeruli.
- The excess is absorbed in the proximal convoluted tubules.
- The free hemoglobin can filter out and appears in the urine as hemoglobinuria.
- 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:
- The small amount of hemoglobin in urine does not give visible color, which can be detected by the dipstick method.
- O-toluidine gives a blue color to hemoglobin.
- This also detects myoglobin.
- The false-positive test is seen in the following:
- If the container contains hypochlorite, an oxidizing agent.
- The false-negative test is seen in the following:
- Vitamin C (ascorbic acid).
- Sensitivity is low when there are high specific gravity and a high concentration of nitrite.
- Benzidine test is not used because this is a carcinogenic agent.
|Characteristics||Orthotolidine method||Benzidine method
- In case of positive urine for occult blood but no RBCs are seen under the microscope, suspect myoglobinuria.
- This occurs as a result of muscle injury, muscle disease disorder, and some poisoning.
This test detects:
Blood in the urine indicates damage to the kidneys or the urinary tract.
The normal value of urine hemoglobin
- Normally Hemoglobin is negative in the urine.
- <0.03 mg free Hb/dL.
Causes of Hemoglobinuria:
- It is positive for all causes of hematuria e.g
- Renal calculi.
- Exposure to toxic drugs.
- Intravascular hemolysis.
- Pregnancy and in puerpera.
- Transfusion reaction.
- Kidney infarction.
- Extensive burns.
- Paroxysmal nocturnal hemoglobinuria.
- Drugs and poison, e.g., sulfonamides, quinine, phenylhydrazine, poisonous snake, and fava beans.
- Infections, e.g., malaria, blackwater fever, gas gangrene, yellow fever, and anthrax.
- Direct trauma to RBC like exercise, heart valve prosthesis.
- Microangiopathic hemolytic anemia.
- Disseminated intravascular coagulopathy.
- Hemolysis in the donor blood due to improper storage.
Urine differentiation between the presence of RBCs, Hemoglobin, and Myoglobin:
|Reagent strip for blood||Positive||Positive||Positive|
|Urine color||Cloudy red||Red, clear||Clear, red-brown|
|Plasma color||Normal||Pink to red||Normal|
|Presence of RBCs||Present||Absent (± few)||Absent (± few)|
|LD4 and LD5||Normal||Normal||Raised|
|LD1 and LD2||Normal||Raised||Normal|
|Total CK||Normal||A slight increase (10 times the normal)||Markedly increased (40 times the normal)|