Skip to main content

Chemistry

Result Interpretation

Interpreting protein and nitrogen compound test results is a key aspect of clinical diagnostics. These results often reflect the status of the liver, kidneys, nutritional status, and presence of certain diseases. Here’s a guide

  • Total Protein
  • Albumin
  • Prealbumin (Transthyretin)
  • Globulins
  • Albumin/Globulin (A/G) Ratio
  • Blood Urea Nitrogen (BUN)
  • Creatinine
  • Blood Urea Nitrogen/Creatinine Ratio
  • Uric Acid
  • Ammonia
  • Cerebrospinal Fluid (CSF) Protein
  • Urine Protein
  • Protein Electrophoresis (Serum and Urine)
  • Immunofixation Electrophoresis (IFE)
  • Tumor Markers (PSA, AFP, CEA, CA-125, etc.)

Total Protein

  • Reference Interval: 6.0-8.3 g/dL
  • Interpretation
    • Elevated Total Protein (Hyperproteinemia)
      • Dehydration (hemoconcentration)
      • Multiple Myeloma (increased globulins)
      • Chronic Inflammation
    • Decreased Total Protein (Hypoproteinemia)
      • Malnutrition
      • Liver Disease (decreased albumin synthesis)
      • Kidney Disease (protein loss)
      • Inflammation (acute phase response)
  • Clinical Significance
    • Provides a general assessment of protein status
    • Useful in evaluating malnutrition, liver disease, kidney disease, and inflammatory conditions

Albumin

  • Reference Interval: 3.5-5.0 g/dL
  • Interpretation
    • Elevated Albumin
      • Dehydration
    • Decreased Albumin (Hypoalbuminemia)
      • Liver Disease (decreased synthesis)
      • Kidney Disease (protein loss)
      • Malnutrition (decreased protein intake)
      • Inflammation (acute phase response)
      • Protein-Losing Enteropathy (loss of protein from the GI tract)
      • Edema and Ascites: Due to decreased oncotic pressure
  • Clinical Significance
    • Major indicator of liver function
    • Marker of nutritional status
    • Indicator of kidney function and protein loss

Prealbumin (Transthyretin)

  • Reference Interval: 15-36 mg/dL
  • Interpretation
    • Elevated Prealbumin: Not commonly seen
    • Decreased Prealbumin
      • Malnutrition (early indicator)
      • Liver Disease
      • Inflammation (acute phase response)
      • Tissue Damage or Neoplasia: Can falsely increase or decrease prealbumin
  • Clinical Significance
    • More sensitive marker of nutritional status than albumin due to its shorter half-life
    • Useful for monitoring nutritional support

Globulins

  • Calculation: Globulins = Total Protein - Albumin
  • Interpretation
    • Elevated Globulins
      • Chronic Infections
      • Autoimmune Disorders
      • Liver Disease (e.g., cirrhosis)
      • Multiple Myeloma (monoclonal gammopathy)
    • Decreased Globulins
      • Genetic Immunodeficiency Disorders
      • Acquired Immunodeficiency (e.g., HIV/AIDS)
  • Clinical Significance
    • Provide information about immune function and inflammatory processes
    • Important in diagnosing monoclonal gammopathies and immunodeficiency disorders

Albumin/Globulin (A/G) Ratio

  • Calculation: A/G Ratio = Albumin / Globulins
  • Reference Interval: Typically > 1 (1.0-2.0)
  • Interpretation
    • Decreased A/G Ratio (< 1)
      • Liver Disease: Decreased albumin synthesis and increased globulin production
      • Nephrotic Syndrome: Increased albumin loss in urine
      • Multiple Myeloma: Increased globulin production
  • Clinical Significance
    • Helpful in differentiating the causes of abnormal protein levels

Blood Urea Nitrogen (BUN)

  • Reference Interval: 6-20 mg/dL
  • Interpretation
    • Elevated BUN (Azotemia)
      • Kidney Disease (decreased urea excretion)
      • Dehydration (increased urea concentration)
      • High-Protein Diet (increased urea production)
      • Gastrointestinal Bleeding (increased protein breakdown)
      • Heart Failure (decreased renal perfusion)
    • Decreased BUN
      • Liver Disease (decreased urea synthesis)
      • Malnutrition (decreased protein intake)
      • Overhydration
  • Clinical Significance
    • Assessment of kidney function
    • Evaluation of hydration status
    • Useful in diagnosing liver disease and gastrointestinal bleeding

Creatinine

  • Reference Interval: 0.6-1.2 mg/dL (males), 0.5-1.1 mg/dL (females)
  • Interpretation
    • Elevated Creatinine
      • Kidney Disease (decreased creatinine excretion)
      • Dehydration (increased creatinine concentration)
      • Muscle Breakdown (increased creatinine production)
      • Certain Medications (e.g., NSAIDs, ACE inhibitors)
    • Decreased Creatinine
      • Decreased Muscle Mass
      • Pregnancy
      • Malnutrition
  • Clinical Significance
    • Major Indicator of kidney function
    • Useful for staging chronic kidney disease
    • Used to calculate estimated glomerular filtration rate (eGFR)

Blood Urea Nitrogen/Creatinine Ratio

  • Calculation: BUN/Creatinine Ratio = BUN (mg/dL) / Creatinine (mg/dL)
  • Reference Interval: 10:1 to 20:1
  • Interpretation
    • Increased BUN/Creatinine Ratio
      • Pre-Renal Azotemia: Dehydration, heart failure, gastrointestinal bleeding
      • Post-Renal Azotemia: Urinary tract obstruction
    • Decreased BUN/Creatinine Ratio
      • Liver Disease
      • Malnutrition
      • Low-Protein Diet
      • Acute Tubular Necrosis: In early stages
  • Clinical Significance
    • Helps differentiate between the causes of elevated BUN and creatinine

Uric Acid

  • Reference Interval
    • Males: 3.5-7.2 mg/dL
    • Females: 2.6-6.0 mg/dL
  • Interpretation
    • Elevated Uric Acid (Hyperuricemia)
      • Gout
      • Kidney Disease (decreased uric acid excretion)
      • High-Purine Diet (increased uric acid production)
      • Tumor Lysis Syndrome (rapid cell breakdown)
      • Certain Medications (e.g., diuretics)
    • Decreased Uric Acid (Hypouricemia)
      • Certain Medications (e.g., allopurinol)
      • Liver Disease
      • Xanthine Oxidase Deficiency
  • Clinical Significance
    • Diagnosis and management of gout
    • Assessment of kidney function
    • Monitoring of tumor lysis syndrome

Ammonia

  • Reference Interval: 10-80 μg/dL
  • Interpretation
    • Elevated Ammonia (Hyperammonemia)
      • Liver Failure
      • Urea Cycle Disorders
      • Reye’s Syndrome
      • Hepatic Encephalopathy
    • Decreased Ammonia: Not clinically significant
  • Clinical Significance
    • Assessment of liver function
    • Diagnosis of urea cycle disorders
    • Monitoring of hepatic encephalopathy

Cerebrospinal Fluid (CSF) Protein

  • Reference Interval: 15-45 mg/dL
  • Interpretation
    • Elevated CSF Protein
      • Meningitis
      • Encephalitis
      • Multiple Sclerosis
      • Guillain-Barré Syndrome
      • Tumors
  • Clinical Significance
    • Indicates inflammation or damage to the central nervous system

Urine Protein

  • Reference Interval: < 150 mg/24 hours
  • Interpretation
    • Elevated Urine Protein (Proteinuria)
      • Kidney Disease (e.g., glomerulonephritis, nephrotic syndrome)
      • Diabetes
      • Hypertension
      • Multiple Myeloma
  • Clinical Significance
    • Indicates kidney damage and dysfunction
    • Used to assess the severity of kidney disease

Protein Electrophoresis (Serum and Urine)

  • Interpretation
    • Abnormal patterns in protein electrophoresis can indicate various conditions
    • Monoclonal Spike: Suggests multiple myeloma or other monoclonal gammopathy
    • Decreased Albumin: Suggests liver disease, kidney disease, or malnutrition
    • Increased Alpha-1 Globulins: Suggests acute inflammation
    • Increased Alpha-2 Globulins: Suggests nephrotic syndrome or acute inflammation
    • Increased Gamma Globulins: Suggests chronic infections, autoimmune disorders, or liver disease
  • Clinical Significance
    • Useful for diagnosing monoclonal gammopathies, liver disease, kidney disease, and inflammatory conditions

Immunofixation Electrophoresis (IFE)

  • Interpretation
    • Identifies monoclonal proteins in serum and urine
  • Clinical Significance
    • Confirms the presence of monoclonal proteins suspected by serum protein electrophoresis
    • Essential for diagnosing multiple myeloma and other plasma cell disorders

Tumor Markers (PSA, AFP, CEA, CA-125, etc.)

  • Interpretation
    • Elevated levels suggest the presence of cancer
    • However, tumor markers are not always specific for cancer and can be elevated in benign conditions
  • Clinical Significance
    • Screening: Limited use for screening due to low sensitivity and specificity
    • Diagnosis: Used to support the diagnosis of cancer
    • Prognosis: Can provide information about the prognosis of cancer
    • Monitoring: Used to monitor treatment response and detect disease recurrence

Key Terms

  • Hyperproteinemia: Elevated total protein levels in blood
  • Hypoproteinemia: Abnormally low levels of protein in the blood
  • Proteinuria: Presence of excess protein in urine
  • Albumin: A major protein in the blood
  • Globulin: A group of proteins in the blood
  • BUN: Blood Urea Nitrogen, a measure of urea in the blood
  • Creatinine: A waste product of muscle metabolism
  • Uric Acid: A waste product of purine metabolism
  • Ammonia: A toxic nitrogen-containing compound
  • Glomerulonephritis: Inflammation of the glomeruli, the filtering units in the kidneys
  • Nephrotic Syndrome: A kidney disorder characterized by proteinuria, hypoalbuminemia, and edema
  • Myeloma: A cancer of plasma cells
  • IFE (Immunofixation Electrophoresis): A method to identify monoclonal proteins
  • Tumor Marker: A substance produced by cancer cells or other cells in response to cancer
  • Cardiac Marker: A substance released into the blood when the heart is damaged