Factors affecting measurement of urinary amylase after bladder‐drained pancreas transplantation

Abstract: Urinary amylase activity (UA) was evaluated in 14 diabetic patients receiving bladder‐drained whole pancreas transplants. Amylase was dependent upon pH with optimal activity at pH 7. Increasing acidity led to a substantial loss of measured UA (45% remaining at pH 4, 73% at pH 5, 86% at pH 6, p < 0.001); however, UA was stable at room temperature if the pH was kept constant. On the day after transplantation, a transient peak in UA was followed by a trough lasting a median of 3 days. Thereafter the UA rose steadily, with the rate of rise being faster if the pancreas donor was less than 30 years of age (p < 0.05). Maximal UA values were observed between 3‐6 months after transplantation. High protein and fat liquid test meals, designed to stimulate exocrine secretion, produced an 83% rise in UA (p = 0.02), which was not observed when water was given (n = 8, p = 0.007, differences at 1 hour). Fasting for 17.6 ± 2.1 h (mean ± SEM) produced a 29 ± 6% fall in 24‐h UA, without any measurable change in other parameters of renal or pancreatic function. A fall of 50% in 24‐h UA over 7 d was compared with pancreas biopsy (n = 40) for predicting rejection, and showed a sensitivity of 60% and a specificity of 93%. In 3 patients a false‐negative result occurred in the first few days after transplantation at a time when the UA failed to rise as normally expected. Understanding and eliminating some of the factors which cause variability in UA may improve the interpretation of 24‐h UA measurements in bladder‐drained pancreas allografts.