It's finger lickin' blood! an artefactual cause of raised amylase

摘要

Pre-analytical factors affecting test results are well recognised. We observed a number of cases of significantly increased serum amylase results in children that decreased to normal faster than would have been expected given its known circulating half life. In the majority of cases the results were considered to be random errors and patients were sent home without follow-up investigation. One patient, a two-year old with complex medical problems, presented with unexplained variable increases in serum amylase activity ranging from 206 to 3055 U/L over a six-week period. On questioning it was established that all samples had been obtained from finger prick (capillary) collection and that the child was known to habitually suck his fingers and chew his hands. It was therefore suspected that the high amylase results may have been due to contamination from saliva on the skin. A repeat venous sample, taken two days after the peak amylase result of 3055 U/L had been reported, was normal (78 U/L). Subsequent weekly venous samples have also all been within normal limits. Electrophoresis on a sample with raised amylase from the same child showed it to be predominantly salivary amylase and no macro-amylase was detected.