223 Long Term Follow-up of Patients With Suspected Early Chronic Pancreatitis to Determine the Diagnostic Accuracy of the Secretin Pancreatic Stimulation Test

Background: The diagnosis of chronic pancreatitis in patients with characteristic symptoms but normal pancreatic imaging is challenging. Assessment of pancreatic function through collection of duodenal fluid following secretin stimulation testing (SST) has been advocated in this setting. The diagnostic accuracy of SST in detecting early chronic pancreatitis is not fully known. Aim: To determine if subjects with suspected chronic pancreatitis and abnormal SST subsequently develop histologic or radiographic changes of chronic pancreatitis compared with those with normal SST. Methods: We performed a retrospective review of subjects who received SST at our institution between January 1995 and December 2007 for suspected chronic pancreatitis. All had normal cross sectional and endoscopic imaging of the pancreas prior to SST. A positive test was defined as a peak bicarbonate level of <75mEq/L in duodenal fluid collected over 1 hr following administration of IV secretin. For all subjects, medical records were reviewed for evidence of subsequent development of chronic pancreatitis by imaging and/or pathology from surgical specimens. Subjects were contacted by phone if there was insufficient follow-up by medical records. Patients were then categorized as a ‘true positive', or a ‘true negative' for chronic pancreatitis based on follow-up evidence, allowing for the calculation of sensitivities, specificities, negative predictive value (NPV) and positive predictive value (PPV). Results: 87 subjects with suspected early chronic pancreatitis who underwent SST were reviewed. 60 tested negative and 27 tested positive. Of the 27 patients who tested positive (76% female, average age of 46.6 years), 4 were lost to follow-up. Of the remaining 23 SST positive subjects, 11(48%) developed radiologic or histologic evidence of chronic pancreatitis after a median of 3 years (1-9 years). There was no difference in average or median peak bicarbonate levels (60 mEq/L and 65 mEq/L, respectively) between the group of subjects that developed imaging or histologic evidence of chronic pancreatitis and the group that did not. Of the 60 subjects who tested negative (67% female, average age of 45 years), 13 were lost to follow-up. Of the remaining 47, only one subject was eventually diagnosed with chronic pancreatitis based on subsequent imaging (p<0.001) after a median follow-up period of 6 years (3-11 years). The sensitivity of the SST in diagnosing chronic pancreatitis was 92% with a specificity of 79%; PPV of chronic pancreatitis was 47.8% with a NPV of 97.8%. Conclusions: In imaging-negative patients with suspected chronic pancreatitis, SST is a sensitive predictor of early chronic pancreatitis as well as a highly accurate test for ruling out early chronic pancreatitis with a NPV of 97.8%.