I have broken the zinc results I have measured this year down by centre and
run some simple stats on them. The differences of mean and variance between
centres are very significant. The centres information on primary sample
collection container are listed below together with the mean and SD. Centres
that had sent fewer than 20 samples in the period were excluded from the
analysis. Everyone will draw their own conclusions but the 'Sarstedt' tubes
seem to be the cleanest.
Mean SD Centre Tube
0.642 0.273 A Sarstedt
0.730 0.187 B Sarstedt
0.799 0.240 C Becton Dickinson
0.804 0.501 D Becton Dickinson trace element
0.848 0.111 E LabCo
0.867 0.451 F LabCo
0.906 0.310 G Becton Dickinson
0.947 0.467 H Becton Dickinson
1.066 0.857 I Becton Dickinson
1.604 1.591 J Becton Dickinson
0.911 0.658 All
I M House
Medical Toxicology Unit
Guy's and St Thomas NHS Trust
Avonley Road
London
SE14 5ER
Tel 020 7771 5372
Fax 020 7771 5373
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