engleski

Interlaboratory study of the proficiency of butyrylcholinesterase activity measurements

To assess the ability of laboratories to measure reliably the activity of human serum butyrylcholinesterase (EC 3.1.1.8), a Cholinesterase Proficiency Programme was organised by the Cholinesterase Investigation Unit (Head: Dr. R. T. Evans) of St. James’s University Hospital, Leeds, UK. The project ran from January 1993 until August 1998. Initially, thirty-six laboratories from the United Kingdom, Canada, Croatia, and New Zealand joined the programme. On average fifteen participating laboratories used benzoylcholine as substrate and other used either acetyl-, butyryl-, or propionyl-thiocholine. Activities were measured at 25 0C, 37 0C, or at the room temperature. Samples were distributed to the participants every three months. Because of the wide variation in methodology they were sent in a series of eight. One had a high and one a low activity. The remaining six were mixtures of the two ends in different proportions. The expected results for the six mixtures were calculated for each laboratory from the results reported on the high and low activity sera. The results were presented on a graph on an arbitrary scale from 0 to 10 in which the low activity end sample occupied position 0 and the high end sample position 10. Perfect results for the six mixtures would lie on a straight line which joins end points. The difference between calculated and observed figures was determined and expressed as a percentage of the expected figure. During the programme, 4973 samples were distributed and 596 reports returned (95% of the samples were analysed). In 170 reports the spread of the results was within 5% of the expected figures while 211 had at least one activity exceeding the spread by more than 10 %. For benzoylcholine activities mean values were calculated ; between laboratories, coefficients of variation ranged from 3.8 to 23 %.

human serum butyrylcholinesterase; measurement reliability

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