- There is generally limited clinical utility. Measurement of total protein is preferred.
- Reference:
- Block DR and Florkowski CM. “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th Edition. By Elsevier Inc. 2018
- 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
- 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.
- Typically used to determine if the fluid may be of pancreatic origin.
- Results should be interpreted with clinical context.
- 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.
- 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
- 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
- High concentration of CEA in cyst fluid is suggestive of malignancy.
- High concentration of CEA in pancreactic cyst fluid is suggestive of mucinous lesions.
- Results should be interpreted with clinical context and reviewed with cytology finding.
- References:
- Block DR and Florkowski CM. “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th Edition. By Elsevier Inc. 2018
- McCarty TR et al. Pancreatic cyst fluid glucose in differentiating mucinous from non-mucinous pancreatic cysts: a systemic review and meta-analysis. Gastrointest Endosc. 2021;94:698-712.
- 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
- 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
- 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
- Amniotic fluid glucose less than 16 mg/dL is suggestive of infection.
- Reference:
- Block DR and Ranke DDH. “Body Fluid Testing” . AACC Inc. 2015.
- Low pancreatic cyst fluid glucose is associated with mucinous lesions.
- Reference:
- McCarty TR et al. Pancreatic cyst fluid glucose in differentiating mucinous from non-mucinous pancreatic cysts: a systemic review and meta-analysis. Gastrointest Endosc. 2021;94:698-712.
- 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
- 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
- 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
- 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” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th Edition. By Elsevier Inc. 2018
- 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
- Can aid in the differentiation of bacterial from aseptic meningitis
- CSF lactate >3.9 mmol/L displays 99% specificity and 93% sensitivity for bacterial meningitis
- CSF lactate may also be increased in states of cerebral hypoxia, ischemia, seizures, or sub-arachnoid hemorrhage
- Reference:
- Block DR and Florkowski CM. “Body Fluids” in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 7th Edition. By Elsevier Inc. 2023
- Huy NT et al. Cerebrospinal fluid lactate concentration to distinguish bacterial from aseptic meningitis: a systemic review and meta-analysis. Crit Care. 2010. doi: 10.1186/cc9395
- Sakushima K et al. Diagnostic accuracy of cerebrospinal fluid lactate for differentiating bacterial meningitis from aseptic meningitis: A meta-analysis. J Infect. 2011. doi: 10.1016/j.jinf.2011.02.010
- 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
- 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
- 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.
- 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
- 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.
- 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
- 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.
- 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
- 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
- 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
- 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
- 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
- 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
- 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 by: Benjamin Andress, PhD, DABCC; 2/21/2025
Reviewed by: Benjamin Andress, PhD, DABCC; 2/21/2025