Red-top tube, gel-barrier tube, or green-top (heparin) tube
Separate serum or plasma from cells within 45 minutes of collection.
Maintain specimen at room temperature.
Causes for Rejection:
Diagnose pancreatitis, more specific for pancreatitis than is serum amylase; diagnose peritonitis, strangulated or infarcted bowel, pancreatic cyst
Urine specimens are inappropriate for lipase. Lipase activity is usually absent in urine, possibly from inactivation of the enzyme.
Serum lipase is usually normal in patients with elevated serum amylase, without pancreatitis, who have peptic ulcer, salivary adenitis, inflammatory bowel disease, intestinal obstruction, and macroamylasemia. Coexistence of increased serum amylase with normal lipase may be a helpful clue to the presence of macroamylasemia.1 Lipase is elevated with amylase in acute pancreatitis, but the elevation of lipase is more prolonged.
In work-up of pancreatitis, in addition to serum lipase and amylase, the 2-hour urine amylase is of value. Electrolytes, serum calcium, glucose, and acetone are also often needed. Immunoreactive trypsin is technically more difficult than lipase and probably no better.2 The serum lipase:amylase ratio may help distinguish alcoholic from nonalcoholic pancreatitis. Ratios >2 (expressed as multiples of the upper limits of normal) suggest an alcoholic etiology.3 Lipase isoform or isoenzymes have been studied.4
1. Andrews PA, Thomas PA, “Macroamylasaemia as a Cause of Persistently Raised Serum Amylase,” Br J Surg, 1988, 75(10):1035. PubMed 2464398
2. Lott JA, Speicher CE, Nemesánszky E, “Is Serum Amylase an Obsolete Test in the Diagnosis of Acute Pancreatitis?” Arch Pathol Lab Med, 1985, 109(4):314-5. PubMed 2580500
3. Gumaste VV, Dave PB, Weissman D, et al, “Lipase:Amylase Ratio. A New Index That Distinguishes Acute Episodes of Alcoholic From Nonalcoholic Acute Pancreatitis,” Gastroenterology, 1991, 101(6):1361-6. PubMed 1718808
4. Lott JA, Lu CJ, “Lipase Isoforms and Amylase Isoenzymes: Assays and Application in the Diagnosis of Acute Pancreatitis,” Clin Chem, 1991, 37(3):361-8.PubMed 1706232