A comparison of serum amylase isoenzyme determination and serum carotene for the evaluation of exocrine pancreatic insufficiency in cystic fibrosis

A new, specific, and quantitative method for determination of serum pancreatic amylase (P) isoenzymes has been described, and has been shown to be an accurate indicator of pancreatic insufficiency when compared to standard tests of absorption. Since a major advantage of serum P isoenzyme measurement is the ease with which samples can be obtained (venipuncture), a comparison of this method with other, easily performed screening tests for malabsorption seemed warranted. We therefore retrospectively compared serum P isoenzyme determination to serum carotene levels. All but one of the serum pairs for comparison of these tests were obtained within three months of each other. All patients were on a regular diet. In six of seven patients there was a high degree of correlation (r=0.96) between serum P isoenzyme levels and serum carotene values. The seventh patient, a 19 year old college student being evaluated for recent onset of abdominal pain, had a low serum carotene (39μg/dl; nl=50-300), but an elevated P isoenzyme (21.5 units/1; nl=2.7-9.4). The latter is consistent with acute pancreatitis. Since that time, he has not manifested any symptoms of clinical pancreatic insufficiency, with a normal stool pattern and no requirement for pancreatic enzyme replacement therapy. His abdominal pain resolved spontaneously. On the basis of his clinical course, and the serum P amylase isoenzyme, it was felt that he had undergone an episode of acute pancreatitis. We conclude that in most CF patients, there is a good correlation between P isoenzyme levels and serum carotene, but that in some patients whose clinical picture is ambiguous serum P isoenzyme may provide diagnostic information not available with serum carotene determinations.