New Urinary Test for Acute Pancreatitis
ABSTRACT & COMMENTARY
Synopsis: A new urinary test for detecting acute pancreatitis is better than blood or urinary amylase.
Source: Kemppainen EA, et al. N Engl J Med 1997;336: 1788-1793.
Severe acute pancreatitis is a common condition, especially at urban public hospitals. The differential diagnosis is large. The use of amylase and lipase blood and/or urine assays have sub-optimal test characteristics with frequent false-positives and -negatives. Contract-enhanced computer tomography is currently the most accurate, non-surgical test, but it is financially and labor intensive. A fast, accurate, and low-cost test would be a major advance.
Finnish investigators have reported their prospective evaluation of a new urinary assay that measures trypsinogen-2. Trypsinogen is a pancreatic proteinase with two isoenzymes. A small amount of the enzyme escapes from the biliary tree into the circulation where it is subsequently filtered by the renal glomeruli. The investigators developed a rapid dipstick test for detecting elevated trypsinogen-2 concentrations in urine and prospectively evaluated its utility at two large Finnish hospitals.
A total of 500 consecutive adult patients with acute abdominal pain were studied. No one was excluded. All patients had blood and urine amylase tests as well as trypsinogen-2 levels. Selected patients had abdominal CT. Acute pancreatitis and its severity were defined by international consensus criteria that did not include amylase levels. Fifty-three patients were diagnosed with acute pancreatitis; 50/53 (94% sensitivity) had a positive urinary trypsinogen-2 (> 50 ng/mL), and 21/447 had a false-positive test (95% specificity). The amylase testing at various thresholds never had a sensitivity exceeding 85%.
COMMENT BY BRUCE E. HILLNER, MD
This is a straightforward, uncomplicated evaluation of a new diagnostic test with no exclusions, dropouts, or obvious confounders. If this assay, when it becomes commercially available, is priced reasonably, it should randomly diffuse into routine practice.