Dear Peter
1) There is an obscure association between primary
hyperparathyroidism and polycythemia (either PRV or secondary).
PTH is also involved somehow in erthropoiesis and possibly
erythropoietin secretion, and does change with venesection. I
forget how it works.
2) Spin the sample and do a serum ionised calcium (keeping it as
anaerobic as possible).
3) I tend to disbelieve ionised calcium results in any case
unless there is good reason to know that the setup is validated
and the system is used routinely rather than as a neglected
bolt-on to a blood gas analyser (where is the reference interval
from, is there EQA, what type of heparin was used in the
syringe?).
4) What is his acid base status.
Aubrey Blumsohn
PS> Biochemists usually sit up when they find a young person with
PS> hypercalcaemia.This 31-year old man has Calciums , adjusted
PS> for albumin consistently between 2.7 and 2.8 mmol/l.
PS> Unadjusted 2.75 to 2.90.The complication is that he has
PS> Eisenmenger's syndrome ( cyanotic congenital heart disease )
PS> which ,in his case is not amenable to surgical correction.In
PS> recent years he has been polycythaemic and has had a stroke
PS> but thankfully made a complete recovery.His polycythaemia is
PS> controlled by venesections and he takes aspirin,pholcodeine,
PS> mebeverine and a short acting nitrate. Today his Haemoglobin
PS> is 14.6 with a PCV of 50%.Ionised calcium ,using the Bayer
PS> 865 is 1.17 mmol/l which is at the quoted lower limit of
PS> normal.I took him to the machine in ITU and collected the
PS> sample myself.I saw him today to collect a PTH sample but
PS> think it is most likely due to a matrix efect.Does anyone
PS> have anything to say about this?
Regards
Aubrey Blumsohn
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