Pancreatic cancer versus chronic pancreatitis: diagnosis with CA 19-9 assessment, US, CT, and CT-guided fine-needle biopsy. The authors prospectively performed serum CA 19-9 assessment, ultrasound (US), computed tomography (CT), and CT-guided fine-needle aspiration biopsy (FNAB) of the pancreas in 81 consecutive patients with suspected chronic pancreatitis or pancreatic neoplasm. The final diagnosis was pancreatic cancer in 54 patients and chronic pancreatitis in 27 patients. CA 19-9 assessment, US, CT, and FNAB were considered nondiagnostic, respectively, in 0%, 25%, 19%, and 6% of cases. When a definite diagnosis was rendered, the positive predictive value was 90% for CA 19-9 assessment, 95% for US, 98% for CT, and 100% for FNAB; the negative predictive value was, respectively, 69%, 95%, 86%, and 100%. The accuracy of all diagnostic and nondiagnostic studies was 81% for CA 19-9 assessment, 72% for US, 77% for CT, and 94% for FNAB. It is concluded that CT-guided pancreatic FNAB is the most reliable examination for enabling differential diagnosis of pancreatic cancer and chronic pancreatitis. When the pancreas is well visualized at US, the negative predictive value for pancreatic cancer is more accurate than that of CA 19-9 assessment and CT. 