A patient actively vomiting is wheeled into your ED. Within minutes IV access is obtained, and your nurse asks what tests and medicines are wanted. A liter of normal saline, ondansetron, and an H2 blocker are easy, but what labs to order? I think we can all agree on a metabolic profile to look at electrolytes and liver function tests, and a lipase level to assess for pancreatitis. But what about an amylase level?
Originally from Clinical Monster blog
It is known to increase in pancreatitis, but we are already ordering a lipase level. Are we just ordering two tests for the same purpose? Which is better and does it help to order both?
Sensitivity of Amylase For Pancreatitis
In one study , among patients diagnosed with alcohol pancreatitis, 32% had a NORMAL amylase level!
A second paper by Clavien et al , found that 20% of people with pancreatitis on CT had normal initial amylase levels in the ED upon their arrival. However of those 20%, 88% had an elevated lipase. Here, amylase levels were much less sensitive if the patient presented with:
- A longer duration of symptoms
- Alcoholic pancreatitis
- Chronic pancreatitis
More studies have supported the above findings. Amylase  levels returned to normal much faster than lipase levels in acute pancreatitis, some within 24 hours. Amylase  levels rise less high and less often, and return to normal sooner in alcohol pancreatitis compared to gallstone pancreatitis. Amylase  levels are often spuriously normal in cases of hypertriglyceridemia induced pancreatitis. Lastly, one study  found a 91% decrease in amylase production vs a 26% decrease in lipase production in patients with chronic pancreatitis.
Conclusion: Amylase does not have a high sensitivity in pancreatitis, except in the specific case of gallstone pancreatitis presenting less than 24 hours after symptom onset.
Specificity of Amylase for Pancreatitis
According to a review article , serum amylase is elevated often in:
- Celiac disease
- Ulcerative colitis
- Rheumatoid arthritis
- Monoclonal gammopathy
- Renal failure
- Ectopic pregnancy
- Bowel obstruction/infarction
- Tumors involving/inflitrating the salivary glands
- Amylase producing tumors
Unfortunately in comparison lipase is also elevated in HIV, diabetic ketoacidosis, bowel obstruction/infarction, and renal failure – a shorter list, but still not 100% specific. In the review, the specificity of lipase was quite different across all the papers reviewed. Possible sources of this difference may have been the cut-off used for an abnormal value, the type of assay used, and other differences possibly related to the pancreatitis’ etiology.
Conclusion: Specificity is not great for amylase. It may not be great for lipase either. Lipase is at least as specific, possibly more so.
Comparison of Amylase Versus Lipase
A retrospective chart review  examined 1,000 pancreatitis patients. Receiver operator curves showed improved diagnostic accuracy of lipase over amylase using lipase >208 U/L, (normal< 190 U/L). 20% of patients did not have elevated amylase on their initial ED visit, while only 3% did not have an elevated lipase.
A review compared various papers’ sensitivities of lipase vs amylase – 95% vs 79%, 100% vs 72%, 100% vs 55%. And concluded that:
“The cumulative literature supports the replacement of amylase with lipase .”
So lipase is better than amylase. But are both better than lipase alone?
One study  that validated lipase’s increased sensitivity compared to amylase also discovered that evaluating the amylase level in addition to the lipase level “does not enhance discrimination of acute pancreatitis”.
A review  declared that 6 different papers have concluded that there is no benefit to adding amylase to lipase and declare that “the obtaining of both serum amylase and lipase levels is not warranted.”
So… STOP ORDERING AMYLASE
This information is apparently so common knowledge that there is actually a paper  published on the best way to stop EM doctors from ordering amylase. One analysis showed 93% of patients with lipase ordered had amylase ordered as well pre-intervention. An educational intervention was unsuccessful at decreasing the concomitant ordering of amylase! Only by removing amylase from the order sets, did they find a significant decrease in amylase orders – down to 25%. Removing it from the pre-set “trauma labs” labs lowered it even more – to 14%.
Stop ordering an amylase level. Of the two tests for pancreatitis, lipase is better. Adding an amylase to the lipase does not help. Education interventions such as lectures (or writing a blog about it), does not seem to reduce ED physicians ordering amylase. A more effective stratagem seems to involve removing from the electronic medical order sets.
Reprinted with permission from clinicalmonster.com/blog
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