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Editor,—I read with interest a recent study by Löser et al (Gut 1996; 39:580–6). This detailed and well designed study compares a new tubeless test of pancreatic function, faecal pancreatic elastase 1 (FPE1) assay, against the secretin test which is the accepted gold standard pancreatic function test. It had very good sensitivity and specificity for pancreatic insufficiency, confirmed by the secretin test and the presence of steatorrhoea. The FPE1 assay in mild chronic pancreatitis, abnormal function but no steatorrhoea, had a much lower sensitivity of 63%. These results are not entirely different from our pilot study.1 The majority (nine of 14) of our chronic pancreatitis subjects were diagnosed by the secretin test and not anatomical/radiographic criteria only. The other five subjects without a secretin test had chronic pancreatitis based on ERP, pancreatic calcifications and postpancreatic surgery. We did not have mild, moderate and severe categories. We chose to separate our patients with chronic pancreatitis into two groups, severe and moderate, based on an abnormal secretin test and the presence or absence of steatorrhoea or maldigestion. We found that in those with chronic pancreatits and no evidence of maldigestion (our moderate group) the FPE1 was normal in four of seven subjects and no values were in the range 100–200 μg/g of stool, the proposed concentration of FPE1 for moderate chronic pancreatitis. In our disease control group (steatorrhoea from non-pancreatic aetiologies), four of seven subjects had abnormal FPE1 concentrations. This group was chosen as a key clinical decision point is to decide whether or not steatorrhoea results from pancreatic insufficiency. In the study by Löser et al, false positive results were also detected in the control group (gastrointestinal diseases of non-pancreatic origin). We wonder whether these subjects had steatorrhoea?
The characteristics of pancreatic elastase 1, as well as the simplicity of using the FPE1 assay (ScheBo Tech), do support the clinical usefulness of this assay. Indeed, Löser et al’s larger and well designed study shows that the test works well overall, but in the group most difficult to diagnose, it may be less sensitive. This group of patients with chronic pancreatitis present primarily with pain but without steatorrhoea. They typically have normal pancreatic ducts on ERP, and are best diagnosed using the secretin test. We believe the secretin test is easy to use and is not significantly more invasive than a nasogastric tube. It is devoid of any real complications2 and correlates very well with the true gold standard, histology.3
Editor,—The clinical relevance of a pancreatic function test is strongly related to its sensitivity and specificity in mild and moderate cases of exocrine pancreatic insufficiency, as severe cases with progressive steatorrhoea are rarely a challenge in clinical practice. In our study all 14 patients with moderate exocrine insufficiency, defined as decreased ecbolic and hydrokinetic function in the secretin-caerulein test, but no steatorrhoea, had significantly decreased feacal elastase 1 concentrations, giving 100% sensitivity in moderate cases. In patients with a partial decrease in ecbolic pancreatic function but no disturbance of hydrokinetic function and no steatorrhoea, the sensitivity was 63%. Though this is a limited sensitivity for mild cases, it is by far the highest sensitivity reported to date for an indirect pancreatic function test. These data are actually confirmed by the results of further studies (see references 13–16, 26, 28).
We agree with Drs Amann and Toskes that the secretin test is not as difficult to use as thought by many clinicians, but there is no doubt that the FPE1 assay is more practical and easier to use. The secretin test is invasive, time consuming, uncomfortable for the patient, is not an international standard (this test procedure is uncommon in Europe), and is more expensive than the FPE1 assay. Despite certain limitations in very mild cases of exocrine pancreatic insufficiency, measurement of the faecal elastase 1 concentration is actually the most sensitive and most specific indirect pancreatic function test available.
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