Advice please.
We have a case of a 19 year old male; at baseline PTH 65.3 pmol/L and
adjusted calcium 3.56 mmol/L (RR 2.15 - 2.50; Integra 800). Parathyroid
adenoma removed, intra-op PTH 29, 3 days later 11.1 pmol/L, where it has
stayed since. Ca(adj) fell to 2.17, Ca(ionised) 1.20 (1.12 - 1.32mmol/L). We
use Elecsys 2010 for PTH (RR 1.5 - 6.5) and EDTA plasma samples.
On the PTH result being queried the sample was re-assayed by Immulite 2000,
which gave 2.0 pmol/L. On a new sample both assays gave results similar to
their results on the original sample. In the Elecsys assay the PTH diluted
parallel to a control patient's sample. Dilution on the Immulite gave the
expected result, ruling out the possibility of excess EDTA from an
underfilled tube interfering in the alk phos signal system (so I am told).
Adding the specimen to heterophilic antibody binding tubes (Scantibodies)
did not alter the PTH result that we obtained on the Elecsys (difference was
3%).
Is anyone aware of such discrepancies between Elecsys and Immulite PTH
results?
Thanks
Paul Chubb
Fremantle Hospital
Western Australia
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