Blood Work Questions

Posted by cj on July 19, 2006 at 12:51:57:
In Reply to: blood work question?? posted by jeff

Lab Studies:
Blood tests
**Elevations of serum amylase and lipase are found only during acute attacks of pancreatitis, usually early in the course of the disease**In the later stages of chronic pancreatitis, atrophy of the pancreatic parenchyma can result in serum
enzyme levels within the reference range, even during acute attacks of pain.
While low concentrations of serum trypsin are relatively specific for advanced chronic pancreatitis, they are not sensitive enough to be helpful in most patients with mild-to-moderate disease.
Laboratory studies to identify causative factors include serum calcium and triglyceride levels.
When common etiologies are not found, research protocols are available to test for genetic mutations in cationic trypsinogen and CFTR.
Fecal tests
Because maldigestion and malabsorption do not occur until more than 90% of the pancreas has been destroyed, steatorrhea is a manifestation of advanced chronic pancreatitis, and neither qualitative nor quantitative fecal fat analysis can detect early disease.
Assays of fecal chymotrypsin and human pancreatic elastase 1 have the same limitations but are useful in confirming advanced chronic pancreatitis with exocrine insufficiency.
Pancreatic function tests
Direct tests: These tests are the most sensitive and can be used to detect chronic pancreatitis at its earliest stage; however, they are somewhat invasive, labor intensive, and expensive.

Determination in duodenal aspirates: Intubation of the duodenum usually is performed with a Dreiling tube, which allows for separate aspiration of gastric and duodenal contents. The methodology varies depending on the specific laboratory; however, the authors generally use exogenous secretin with cerulein or cholecystokinin to achieve maximal stimulation of the pancreas. The output of pancreatic bicarbonate, protease, amylase, and lipase then is measured in the duodenal aspirates. This test currently only is available in specialized centers. While the greatest sensitivity can be obtained in prolonged infusions of secretagogue to uncover a decreased pancreatic secretory reserve, it is impractical for general clinical use.

Determination in pancreatic juice: This test generally is performed in conjunction with an endoscopic retrograde cholangiopancreatography (ERCP). The pancreatic duct is freely cannulated, an exogenous secretagogue is administered as above, and the pancreatic juice then is aspirated out of the duct as it is produced. The output of pancreatic bicarbonate, protease, amylase, and lipase are measured. This test is gaining popularity because most patients undergo ERCP at some point in their evaluation.
Indirect tests: Noninvasive tests of pancreatic function have been developed for detecting chronic pancreatitis. In principle, these tests work via oral administration of a complex substance that is hydrolyzed by a specific pancreatic enzyme to release a marker substance. The intestine absorbs the marker, which then is measured in the serum or urine. These tests are capable of detecting moderate-to-severe chronic pancreatitis. The presence of renal, intestinal, and liver disease may interfere with the accuracy of these tests. Neither currently is freely available in the United States.
http://www.emedicine.com/med/topic1721.htm