We encountered a problem, but less extreme in a patient who presented with
myeloma 18 months ago. Total calcium was 3.19mmol/l, Adjusted Calcium
3.47mmol/l. The patient was asymptomatic which our (astute) Haematologist
believed was out of keeping with the calcium results. Ionised calcium was
normal at 1.27mmol/l. The patient had a large IgA kappa paraprotein (65g/l)
and still has this abnormality on her latest results this month(TCa 3.02,
AdjCa 3.22, ICa 1.17, M-Protein 59g/l). Following treatment last year when
her paraprotein level dropped to 12g/l her calcium returned to normal (TCa
2.26, AdjCa 2.22) but it has progressively crept back up since then as the
paraprotein level has increased. I'd be interested to know how common these
are. Obviously everyone should demand to have ionised calcium available for
confirmation of true hypercalcaemia before embarking on treatment in
asymptomatic hypercalcaemic patients.
-----Original Message-----
From: Mohammad Al-Jubouri [mailto:[log in to unmask]]
Sent: 17 April 2000 04:07
To: [log in to unmask]
Subject: Spurious hypercalcaemia
Dear all
I wish to share this interesting case with you. Last
week, a high serum calcium of 4.11 mmol/L was brought
to me to deal with. The result belongs to a
66-year-old gentleman who was admitted to a surgical
ward because of right upper quadrant pain. The
surgical Spr told me that the patient is fully
conscious, orientated, has no polyuria or polydipsia
with no clinical evidence of malignancy and is feeling
well in himself. Despite this, I told him that he
should be managed as a hypercalcaemic crisis which is
probably due to underlying malignancy. Meanwhile, a
serum protein electrophoresis was performed which
showed an intense paraprotein band (57 g/L)which
immunofixed as IgG lambda. A random urine sample
showed heavy Bence-Jones proteinuria (3.5 g/L). The
patient received 90 mg pamidronate infusion and his
repeat calcium 24 hours late was 4.23 mmol/L!! To
investigate the possibility of spurious hypercalcamia,
the immunoglobulins were precipitated from the sample
by PEG and calcium was re-measured in the supernatant
which gave a result of 2.34 mmol/L. It became obvious
that this hypercalcaemia was spurious due to binding
of the calcium to the paraprotein molecules. The other
clues which point to this phenomenon are the absence
of clinical features of severe hypercalcaemia and
failure of response to pamidronate infusion. Ionised
calcium measurement would have picked up this
instataneously, but we do not have this assay. So far,
I have seen at least 3 such cases associated with
paraproteinaemia, yet this phenomenon is not widely
described in the literature. Comments regarding
similar experience are welcome.
Regards.
=====
Dr. M A Al-Jubouri
Consultant Chemical Pathologist
Whiston Hospital
Prescot
Merseyside L35 5DR
UK
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