A Critical Evaluation of Laboratory Tests in Acute Pancreatitis Dhiraj Yadav, M.D., N. Agarwal, M.D., F.R.C.S., and C. S. Pitchumoni, M.D., M.A.C.G. Division of Gastroenterology and Department of Surgery, Our Lady of Mercy University Medical Center, New York Medical College, Bronx, New York ABSTRACT An ideal laboratory test in the evaluation of a patient with acute pancreatitis (AP) should, in addition to accurately establishing the diagnosis of AP, provide early assessment of its severity and identify the etiology. None of the tests available today meet all these criteria, and presently there is no biochemical test that can be considered the “gold stan- dard” for the diagnosis and assessment of severity of AP. In the diagnosis of AP, serum amylase and lipase remain important tests. Advantages of amylase estimation are its technical simplicity, easy availability, and high sensitivity. However, its greatest disadvantage is its low specificity. A normal amylase would usually exclude the diagnosis of AP, with the exception of AP secondary to hyperlipidemia, acute exacerbation of chronic pancreatitis, and when the estima- tion of amylase is delayed in the course of the disease. The major advantage of lipase is an increased sensitivity in acute alcoholic pancreatitis and in patients who initially present to the emergency room days after the onset of the disease, as lipase remains elevated longer than amylase. Although once considered to be specific for AP, nonspecific elevations of lipase have been reported in almost as many disorders as amylase, thus decreasing its specificity. Simultaneous esti- mation of amylase and lipase does not improve the accu- racy. Other enzymes for the diagnosis of AP—pancreatic isoamylase, immunoreactive trypsin, and elastase—are more cumbersome and expensive and have no clear role in the diagnosis of AP. No enzyme assay has a predictive role in determining the severity or etiology of AP. Once the diagnosis of AP is established, daily measurements of en- zymes have no value in assessing the clinical progress of the patient or ultimate prognosis and should be discouraged. A host of new serological and urinary markers have been investigated in the last few years. Their main use is in predicting the severity of AP. At present, serum C-reactive protein at 48 h is the best available laboratory marker of severity. Urinary trypsinogen activation peptides within 12–24 h of onset of AP are able to predict the severity but are not widely available. Serum interleukins 6 and 8 seem promising but remain experimental. (Am J Gastroenterol 2002;97:1309 –1318. © 2002 by Am. Coll. of Gastroenter- ology) INTRODUCTION The diagnostic tests in the evaluation of a patient with suspected acute pancreatitis (AP) must answer three ques- tions sufficiently early in the course of the disease: first and foremost, the tests should establish the diagnosis accurately, excluding other conditions that mimic AP with or without hyperamylasemia. Second, at the earliest they should pro- vide an assessment of severity of AP to provide appropriate treatment in the required setting: intensive care unit versus a regular floor or by an internist alone versus a team of medical specialists that includes a surgeon, radiologist, and gastroenterologist trained in therapeutic endoscopy. Third, tests should also help in establishing the etiology for AP, so as to offer a definitive treatment such as cholecystectomy and/or to prevent recurrences of AP, as in the case of a patient with hyperlipidemic AP. The tests should be easily available, cost-effective, and easily repeatable. Obviously, every patient should not undergo all tests. This article, an extension of a number of recent reviews on the topic, including ours published in 1990 in this journal (1), critically evaluates the standard serum and urine tests and discusses the advances in laboratory technology that may have new diagnostic possibilities. In addition to our previous article on this topic (1), we have included relevant articles after 1990, using a broad-based MEDLINE search using the terms acute pancreatitis, diagnosis, laboratory tests, and severity. Relevant articles as well as their refer- ences were reviewed. SERUM TESTS FOR DIAGNOSIS OF AP A host of serum enzymes such as amylase, lipase, trypsino- gen, elastase, phospholipase A 2 , ribonuclease, etc are avail- able to diagnose AP and/or to assess the severity, but ele- vated amylase levels continue to be the “gold standard” among the serum markers. Serum Amylase In AP, serum amylase rises as a result of both increased release and, to some extent, reduced catabolism. The most familiar units of expression are the Somogyi unit (SU) and the international unit (IU). One SU per 100 ml is equivalent to 1.85 IU/L. The normal values are 60 –160 SU/100 ml or THE AMERICAN JOURNAL OF GASTROENTEROLOGY Vol. 97, No. 6, 2002 © 2002 by Am. Coll. of Gastroenterology ISSN 0002-9270/02/$22.00 Published by Elsevier Science Inc. PII S0002-9270(02)04122-9