Body Fluid Testing - Reference Interval and Clinical Indications

OpenAlbumin

Pericardial Fluid

  • There is generally limited clinical utility. Measurement of total protein is preferred.

Peritoneal Fluid

  • Can be used as a marker of portal hypertension
  • High SAAG (serum-ascites albumin gradient) of greater or equal to 11 g/L occurs with
    • Cirrhosis
    • Fulminant hepatic failure
    • Fatty Lier
    • Alcoholic hepatitis
    • Portal vein thrombosis
    • Venoocclusive disease
  • Low SAAG of less than 11 g/L occurs with
    • Peritoneal carcinomatosis
    • Tuberculosis
    • Pancreatic
    • Connective tissue disease
    • Nephrotic syndrome
    • Biliary (without cirrhosis)
  • Reference:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

Pleural Fluid

  • Can be used to differentiate transudates vs exudates
  • Transudates should have a serum to pleural fluid albumin gradient (serum albumin – pleural fluid albumin) greater than 1.2 g/dL
  • Reference:
    • Block DR and Florkowski CM.  "Body Fluids" in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc. 2018.

OpenAmylase

Cyst Fluid

  • Typically used to determine if the fluid may be of pancreatic origin.
  • Results should be interpreted with clinical context.

Drain

  • May aid in the identification of pancreatic fistulas.  Result should be interpreted with serum or plasma amylase activity. 
  • Reference:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

Peritoneal Fluid

  • Normal peritoneal fluid amylase activity is comparable to serum or plasma amylase activity.
  • Greater than 5-fold elevation compared to serum or plasma supports pancreatic ascites.
  • Not recommended for routine evaluation of ascites due to low prevalence of pancreatic ascites. 
  • Elevation may be seen in patients with small bowel perforation, ischemia, or mesenteric thrombosis.   
  • References:
    • Karcher DS and McPherson RA. “Cerebrospinal, Synovial, Serous Body Fluids, and Alternative Specimens” in Henry’s Clinical Diagnosis and Management by Laboratory Methods. 23rd Edition. By Elsevier Inc. 2017.
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018
    • Block DR and Ranke DDH. “Body Fluid Testing”.  AACC Inc. 2015.

Pleural Fluid

  • Aid in the diagnosis of pancreatitis
  • High amylase level typically occurs with
    • Pancreatitis
    • Esophageal rupture
    • Malignancy
    • Pneumonia
    • Liver cirrhosis
  • Reference:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

OpenBilirubin

Drain

  • Aids in the determination of bile leakage
  • Bilirubin concentration fluid-to-serum ratio > 5 is indicative of bile leaks.
  • Reference:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

Peritoneal Fluid

  • Aids in the determination of bile leakage
  • Bilirubin concentration fluid-to-serum ratio > 5 is indicative of bile leaks.
  • Reference:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

OpenCEA

Cyst Fluid

  • High concentration of CEA in cyst fluid is suggestive of malignancy.
  • Results should be interpreted with clinical context and reviewed with cytology finding.
  • Reference:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

OpenCholesterol

Pleural fluid

  • Often use to aid in the evaluation of Chylothorax and pseudochylothorax
    • Triglyceride greater than 110 mg/dL and cholesterol less than 200 mg/dL is diagnostic of chylothorax
    • Triglyceride less than 50 mg/dL and cholesterol greater than 200 mg/dL is diagnostic of pseudochylothorax
  • Reference:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

OpenCreatinine

Drain

  • Can aid in determining whether sudden drain fluid increase is a result of fistula formation or other renal issue
  • Reference:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

Peritoneal Dialysate

  • Serves as a marker of dialysis adequacy
  • Ratio of creatinine in dialysate to plasma or serum vs time is often used in the peritoneal equilibration test (PET).
  • Reference:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

Peritoneal Fluid

  • Identify specimens contaminated with urine
  • Body fluid creatinine to serum creatinine concentrations greater than 1.0 may suggest specimen is contaminated with urine
  • References:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018
    • Block DR and Ranke DDH. “Body Fluid Testing”.  AACC Inc. 2015

OpenGlucose

Amniotic Fluid

  • Amniotic fluid glucose less than 16 mg/dL is suggestive of infection.
  • Reference:
    • Block DR and Ranke DDH. “Body Fluid Testing”. AACC Inc. 2015.

Drain

  • Aids in the evaluation of infection or malignancy.  Result should be interpreted with serum or plasma glucose result.

Pericardial Fluid

  • Pericardial to serum glucose ratio of less than 1.0 may be helpful in differentiating exudate and transudate.
  • Pericardial glucose less than 40 mg/dL is common in bacterial, tuberculous, rheumatic, or malignant effusions.
  • References:
    • Karcher DS and McPherson RA. “Cerebrospinal, Synovial, Serous Body Fluids, and Alternative Specimens” in Henry’s Clinical Diagnosis and Management by Laboratory Methods. 23rd Edition. By Elsevier Inc. 2017.
    • Block DR and Ranke DDH. “Body Fluid Testing”.  AACC Inc. 2015

Peritoneal Dialysate

  • Serves as a marker of dialysis adequacy.
  • Ratio of glucose in dialysate to plasma or serum vs time is often used in the peritoneal equilibration test (PET).
  • Reference:
    • Block DR and Ranke DH.  “Body Fluid testing” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

Peritoneal Fluid

  • There is generally limited clinical utility.
  • Decreased concentration compared to serum or plasma, in the appropriate clinical context, supports tuberculous peritonitis, peritoneal carcinomatosis or spontaneous bacterial peritonitis.
  • References:
    • Karcher DS and McPherson RA. “Cerebrospinal, Synovial, Serous Body Fluids, and Alternative Specimens” in Henry’s Clinical Diagnosis and Management by Laboratory Methods. 23rd Edition. By Elsevier Inc. 2017.
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

Pleural Fluid

  • Normal pleural fluid has similar glucose concentrations as serum.
  • High pleural fluid glucose (compared to serum) can occur with
    • Esophageal rupture
    • Peritoneal dialysis
  • Reference:
    • Block DR and Florkowski CM.  "Body Fluids&rdquo" in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

Synovial Fluid

  • Sometimes use to aid in the evaluation of joint inflammation and septic arthritis
  • Clear cutoff has not been established and should be reviewed with serum glucose results
  • Reference:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

OpenLactate

Synovial Fluid

  • Can aid in the evaluation of joint inflammation and septic arthritis
  • Clear cutoff has not been established
  • Only L-lactate is measured and not the D-isoform, which may limit the clinical utility of the test.
  • Reference:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

OpenLD

CSF

  • Reference interval: 0-23.5 units/L
  • Non-specific marker of cell necrosis
  • Increase of CSF LDH can occur:
    • Meningitis, with higher increase in bacterial vs viral
    • Primary brain tumors / metastases
    • Hydrocephalus
    • Seizures
    • Hypoxia
    • Cerebral ischemia
  • Reference:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

Pericardial Fluid

  • Helps differentiate transudates from exudates in patients with moderate to large effusions (100 - >500 mL) of unknown origins that do not respond to therapy.  Results are not directly diagnostic and have poor sensitivity.
  • Application of Light’s Criteria to pericardial fluid suggests exudate when one or more of the following criteria are met:
    • Protein: >3.0 g/dL or pericardial fluid to serum ratio greater than 0.5
    • LDH:  >200 mg/dL or pericardial fluid to serum ratio greater than 0.6
  • References:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018
    • Karcher DS and McPherson RA. “Cerebrospinal, Synovial, Serous Body Fluids, and Alternative Specimens” in Henry’s Clinical Diagnosis and Management by Laboratory Methods. 23rd Edition. By Elsevier Inc. 2017.

Peritoneal Fluid

  • Differentiating between transudate and exudate.  No ideal biochemical markers allow for complete discrimination in ascites.  There are no cutoffs.
  • Differentiating secondary bacterial infections from spontaneous bacterial peritonitis
  • Secondary infection is supported when two of the three criteria are met:
    • Total protein greater than 1.0 g/dL
    • Glucose less than 50 mg/dL
    • LDH greater than upper reference limit for serum
  • References:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018
    • Block DR and Ranke DDH. “Body Fluid Testing”.  AACC Inc. 2015
    • Karcher DS and McPherson RA. “Cerebrospinal, Synovial, Serous Body Fluids, and Alternative Specimens” in Henry’s Clinical Diagnosis and Management by Laboratory Methods. 23rd Edition. By Elsevier Inc. 2017

Pleural Fluid

  • Can be used to differentiate transudates vs exudates
  • Based on Light's Criteria, exudates have at least one of the following criteria:
    • pleural fluid to serum protein ratio greater than 0.5
    • pleural fluid to serum LDH ratio greater than 0.6
    • pleural fluid LDH activity greater than 2/3 the upper limit of a normal serum LDH activity
  • References:
    • Block DR and Florkowski CM.  "Body Fluids" in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018.
    • Karcher DS and McPherson RA. “Cerebrospinal, Synovial, Serous Body Fluids, and Alternative Specimens” in Henry’s Clinical Diagnosis and Management by Laboratory Methods. 23rd Edition. By Elsevier Inc. 2017.

Synovial Fluid

  • Can aid in the evaluation of joint inflammation and septic arthritis
  • Clear cutoff has not been established
  • Reference:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

OpenpH

Pleural Fluid

  • Reference interval: 7.60 – 7.66
  • Effusions: < 7.6
  • Transudates: 7.45-7.55 vs exudates 7.30-7.40
  • Acidosis (pH < 7.2) typically occurs with
    • Complicated parapneumonic effusion
    • Esophageal rupture
    • Tuberculosis
    • Rheumatoid disease
    • Haemothroax
    • Urinothorax
    • System acidosis
  • References:
    • Block DR and Florkowski CM. "Body Fluids" in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th Edition. By Elsevier Inc. 2018.
    • Chris Higgins. Clinical aspects of pleural fluid pH. 2009. www.acutecaretesting.org. Accessed 3/8/19.
    • Sobhey KE and Naglaa BA. Diagnostic significance of pleural fluid pH and pCO2. Egyptian J of chest disease and tuberculosis. 2015: 64:877-885.

OpenProtein

Drain

  • There is generally limited clinical utility for the measurement of total protein in drain fluid.
  • Reference:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

Pericardial Fluid

  • Helps differentiate transudates from exudates in patients with moderate to large effusions (100 - >500 mL) of unknown origins that do not respond to therapy.  Results are not directly diagnostic and have poor sensitivity.
  • Application of Light’s Criteria to pericardial fluid suggests exudate when one or more of the following criteria are met:
    • Protein: >3.0 g/dL or pericardial fluid to serum ratio greater than 0.5
    • LDH:  >200 mg/dL or pericardial fluid to serum ratio greater than 0.6
  • Reference:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

Peritoneal Fluid

  • Was traditionally used to differentiate transudates vs exudates
  • However, SAAG (serum ascites albumin gradient) is a more widely accepted use as marker of portal hypertension.
  • Reference:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

Pleural Fluid

  • Can be used to differentiate transudates vs exudates
  • Based on Light’s Criteria, exudates have at least one of the following criteria:
    • pleural fluid to serum protein ratio greater than 0.5
    • pleural fluid to serum LDH ratio greater than 0.6
    • pleural fluid LDH activity greater than 2/3 the upper limit of a normal serum LDH activity
  • Transudates should have a serum to pleural fluid protein gradient (serum protein – pleural fluid protein) greater than 3.1 g/dL
  • Reference:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

Synovial Fluid

  • Can aid in the evaluation of joint inflammation and septic arthritis
  • Clear cutoff has not been established
  • Reference:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

OpenPTH

FNA Needle Washout

  • Often used in conjunction with FNA biopsy to diagnose and localize parathyroid adenomas.
    • FNA-PTH level higher than serum PTH is considered diagnostic of parathyroid adenoma
  • Reference:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

OpenTriglyceride

Pleural Fluid

  • Often use to aid in the evaluation of Chylothorax
    • Triglyceride greater than 110 mg/dL and cholesterol less than 200 mg/dL is diagnostic of chylothorax
    • Triglyceride less than 50 mg/dL and cholesterol greater than 200 mg/dL is diagnostic of pseudochylothorax
  • Reference:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

OpenUrea Nitrogen

Peritoneal Dialysate

  • Serves as a marker of dialysis adequacy.
  • Ratio of urea in dialysate to plasma or serum vs time is often used in the peritoneal equilibration test (PET).
  • Reference:
    • Block DR and Florkowski CM.  “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.  6th Edition.  By Elsevier Inc.  2018

Devised by: Hoi-Ying Elsie Yu, PhD, DABCC; Sheng-Ying (Margaret) Lo, PhD, DABCC;  and Stacy Kenyon, PhD, DABCC; 3/20/2019

Revised: 8/13/2020
Reviewed 12/24/2020

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