Urine protein 24 hours sample, Classification of Proteinuria

March 22, 2021Lab TestsUrine Analysis

Sample

1. Collect a random sample of urine to rule out the presence of protein.
2. 24 hours of urine is collected in a sterile container.
   1. Discard the first sample then collect all other samples for 24 hours.
   2. Add the last sample in the container.
3. Add a few ml of HCL into the container.
4. Also, refrigerate the sample during collection.
5. Centrifuge and adjust to pH 7.0.
   1. Analyze a fresh sample.

Precautions

1. Avoid dehydration due to the lake of fluid intake.
2. Avoid the contamination of urine from the vaginal secretions.
3. Not adequate collection during urinary tract infections (UTI).
4. Use of contrast media in radiology within the last three days.
5. Avoid strenuous exercise.
6. Avoid emotional stress.

Indications

1. The presence of protein in urine is an indicator of renal diseases.
2. This may be done to evaluate the edema.

Pathophysiology

1. Proteins are found in:
   1. Blood.
   2. urine.
   3. CSF.
   4. Amniotic fluid.
   5. Saliva.
   6. Feces.
2. In a healthy individual with normal renal function, there will be no proteins in the urine or may find only traces.
3. Urine protein sources are:
   1. From the blood.
   2. From kidneys.
   3. From the urinary tract.
   4. From vagina and prostate.

Proteinuria classification

Proteinuria classification

Classification of the proteinuria on the basis of the amount of protein excreted in the urine:

Mechanism of protein in the urine:

1. Urine is formed by the ultrafiltration of plasma across the glomeruli.
2. Plasma protein with molecular weight >40,000 is retained in the plasma.
3. Normally glomerular membrane does not allow filtration of protein into the urine because of narrow spaces in the glomerular membrane.
4. In glomerulonephritis, the glomerular membrane is injured and there are larger spaces from where the protein particularly albumin (smaller in size) can easily pass in the urine.

Etiology of Proteinuria

Kidney role in protein excretion

5. Albumin is 1/3 of the urinary protein.
   1. Albumin filtered through glomeruli very easily in comparison to plasma globulin.
6. In pathologic conditions Albumin is abundant.
7. Urine Albumin is used as the protein marker of glomerular permeability.
8. The term proteinuria is often used synonymously for Albuminuria.
9. Protein is the single most important parameter for renal dysfunction.
10. If more than a trace of protein found in urine then advise 24 hours urinary protein.

Normal

Source 1

• 1 to 14 mg/dL
• At rest = 50 to 80 mg/day
• After intense excercise = <250 mg/day

Other sources

• The normal albumin excretion rate is <20 µg/minutes.
  • Or <30 mg/day
• Adult male = 10 to 140 mg /L OR = 1 to 14 mg/dL
  • Adult female = 30 to 100 mg/L OR 3 to 10 mg/dL
• Child < 10 years = 10 to 100 mg/L OR 1 to 10 mg/dL.
• < 150 mg/24 hours.
• Qualitative = normally negative.
  • Significant proteinuria is > 300 mg / 24 hours.

Lab Diagnosis

1. Usually, 24 hours urine sample is needed.
2. Urine protein assays are sensitive to all types of proteins like albumin, globulins, and Bence-Jones protein.
3. Most of the assay can detect a minimum of 3 mg/dL of protein in the urine.
4. Urine dipstick is most commonly used. This is most sensitive to albumin.
   1. The dipstick can detect albumin when it is about 18 mg/dL

Increased proteinuria is seen in:

1. Glomerular diseases : 
   1. Acute and chronic glomerulonephritis.
   2. Nephrotic syndrome.
   3. Polycystic kidney
   4. Amyloidosis.
   5. Autoimmune diseases like SLE.
   6. Diabetes mellitus.
   7. Malignant hypertension.
2. Decreased tubular reabsorption :
   1. Acute and chronic pyelonephritis.
   2. Renal tubular diseases.
   3. Wilson’s disease.
   4. Fanconi’s syndrome.
   5. Interstitial nephritis.
   6. Cystinosis.
3. Other causes are :
   1. Congestive heart failure.
   2. Multiple Myeloma.
   3. Malignant Lymphoma.
   4. Waldenstrom’s macroglobulinemia.
   5. Trauma and stress.
   6. Acute infections like septicemia.
   7. Toxemia of pregnancy.
   8. Hyperthyroidism.
   9. Poisoning from phosphorus, gold, mercury, lead, and phenol.
   10. Drugs like opiates and etc.
   11. Hypertension.
   12. Postural proteinuria.