A-125 Difference Between the Results of Vitros® Dry Biochemistry and Wet Biochemistry with Kinetic Method in Diagnosing the Comorbidity of Lung Adenocarcinoma and Aacroamylasemia: Case Report

Abstract Background Amylase (AMY) is a biomarker that comes mainly from the pancreas and salivary glands. Macroamylasemia is a condition often accompanied by malignant tumors and clinical features that include: (i) recurrent abdominal pain, no abnormality in the salivary glands, serum amylase (AMY) level ≥2 to 3 times higher than the normal value and poor patient response to treatments for pancreatitis; (ii) normal serum creatinine and urea levels, increased serum AMY level, and urine AMY level within the normal range or slightly lower. Because macroamylasemia may cause abnormally increased serum AMY levels for a long period of time, misdiagnosis of pancreatitis and delayed diagnosis/treatment of the disease may occur. We report a case of lung adenocarcinoma with macroamylasemia that was co-diagnosed using wet chemistry with kinetic method and dry chemistry to measure AMY. Methods A 47-year-old male patient was previously diagnosed with “acute pancreatitis and lung infection” after initial admission to a local hospital with paroxysmal cough and abdominal pain without obvious cause. To further diagnose the patient, we determined the blood AMY level by using the wet chemistry with kinetic method and the Vitros® dry chemistry test, in addition to conducting a physical exam, abdominal and chest computed tomography (CT), and other lab tests. Two methods, calculation of amylase/creatinine clearance ratio (Cam/Ccr ratio) and protein precipitation by polyethylene glycol (PEG), were also performed to validate assumed interference by serum macroamylase (MAMS) in the wet chemistry method compared to the dry chemistry method, which has technology to capture large molecules and minimize the impact of interferents. MAMS is a high-molecular-weight AMY complex that is synthesized by normal serum AMY bound with macromolecular substances (eg, immunoglobulins and carbohydrates). Results The final diagnosis was a stage IIB cT3N0M0 adenocarcinoma of the upper lobe of the right lung and macroamylasemia. Symptoms and radiologic findings were atypical in terms of pancreatitis. Serum AMY was 2,178U/L when measured with the wet chemistry with kinetic method. When the specimen was re-tested with Vitros dry chemistry, the AMY level was 369 U/L. After precipitation with 25% PEG 6000 solution, the blood AMY level from wet chemistry decreased from 2395.1 U/L to 246.7 U/L, yielding a precipitation rate of 89.7%. Cam/Ccr ratio was calculated as 0.23% (1%). The calculated PEG precipitation rate and Cam/Ccr ratio from this study were consistent with the ranges considered for macroamylasemia, which are ≥73% and Cam/Ccr ratio 1%, respectively. Conclusions High serum AMY levels do not necessarily indicate pancreatitis or parotitis; wet chemistry results can be impacted by the presence of serum macroamylase. Instead of relying solely on blood AMY in diagnosing acute pancreatitis, clinicians should also consider the correlations of blood AMY with urine AMY and blood lipase. In patients with prolonged blood AMY elevation but normal lipase and urine AMY, re-testing of AMY with a more interference-resistant methodology (e.g. Vitros dry chemistry) may be requested. Accordingly, Cam/Ccr ratio calculation and PEG precipitation can be performed to validate the diagnosis of macroamylasemia.