THE
CASANOVA TEST IN HYPERPARATHYROIDISM
In
patients with a forearm parathyroid autograft (following total parathyroidectomy
for diffuse parathyroid hyperplasia) the so-called ‘Casanova test’ may be
useful in determining recurrence of hyperparathyroidism (HPT) in the forearm
autograft. Initially, a baseline parathormone (PTH) value is drawn from the
non-grafted (usually the dominant) hand. The grafted hand is then rendered
ischemic for 10 min using an elastic bandage, before another blood sample is drawn
from the non-grafted arm. Comparison of the two PTH values is then performed.
1.ARM
RECURRENCE: It is observed in 3 – 67 % of patients (most commonly in inherited HPT
patients [45 – 50 %]) and is indicated by a drop in PTH levels > 50 % after
10 min of grafted arm ischemia
2.NEGATIVE
FOR ARM RECURRENCE: It is indicated by PTH values which remain unchanged or
decrease < 20 % after 10 min of grafter arm ischemia. The negative test suggests
that the source of recurrent HPT is not in the arm and therefore presumed to be
in the neck
3.INDETERMINATE:
Results of the Casanova test are considered as inconclusive when in patients who
have a PTH drop between 20 and 50 %. In this case, additional imaging studies
are necessary to localize the hyperfunctioning parathyroid tissue which may be
in the neck, in the forearm autograft or both
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