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567
positive LR (3.4, 95% CI 1.8–6.3). After excluding
seven women who were taking aspirin, the test proper-
ties of the various platelet cut-off points remained
essentially unchanged (data available upon request).
Notwithstanding the above limitations, these find-
ings do add to a scarce body of literature on the utility
of the platelet count in estimating, but not defining,
the risk for hemorrhage among women with hyperten-
sion in pregnancy before delivery. The CIs around the
estimates were quite narrow, and, assuming that the
high specificity and PPV test properties of a low
platelet count are only somewhat biased, it is likely that
these data can be of some practical use to clinicians.2 1
It has been demonstrated that a prolonged BT pre-
Discussion
Among a large prospective cohort of women with var-
ious forms of hypertension in pregnancy, we found
that fewer than 5% either underwent a BT analysis or
developed a thrombocytopenia below 75 x 109/L
prior to delivery. In a retrospective subgroup analysis
of women within this cohort who underwent a BT, a
platelet count below 75 x 109/L appeared to be mod-
erately insensitive, but very specific, for identifying
those with a prolonged BT.
The decision to also include pregnant women with
non-proteinuric forms of hypertension (i.e., chronic
and gestational hypertension)2 4 was made because we
did not know why these women had a BT ordered,
and thus, could not be certain that they were no more
hypertensive or ill than women with overt proteinuria
(i.e., preeclampsia). Similarly, the finding of non-pro-
teinuric hypertension and thrombocytopenia in a par-
turient may have represented a variant of preeclampsia
in advance of the manifestation of overt proteinuria,
which often develops only at a later stage.2 4
dicts a decline in the hematocrit value, and could be
33,34
indirect evidence of excess hemorrhage
.
However, this concept has been countered by the
observation that anemia itself, in the face of a normal
platelet count, can prolong the BT.1 7 Furthermore, it
is known that the BT may be prolonged due to a vari-
ety of conditions that are independent of platelet
quantity or function.1 7
We have observed that a platelet count of 75
x109/L or less may be quite specific for the presence
of an abnormal BT. When a woman’s platelet count is
below this value, it is unlikely that a BT measurement
can add much to the estimation of bleeding risk, since
our data suggest that the BT will likely be prolonged.
However, a platelet count of 100 x 109/L or greater
is less specific (80%), while remaining insensitive
(66%), for a prolonged BT. At this point, the clinician
may require another method to estimate the probabil-
ity that a bleeding diathesis is present, as well as to
evaluate the risk for a major hemorrhagic event.
Although the risk of traumatic neuraxial hemor-
rhage remains a major issue for the obstetrical anes-
thesiologist,8,9 there are few established risk factors for
this serious but rare event.8,9,35The development of a
spinal hematoma is not guaranteed in the face of a
prolonged BT and would likely remain a rare event
even in the presence of a bleeding diathesis. Increasing
experience and the use of more modern techniques for
neuraxial blockade, including the selective use of a sin-
gle spinal block instead of insertion of an epidural
catheter, could translate into a lower baseline risk for
traumatic hemorrhage. Although our data may aid in
clinical decision-making, we encourage further discus-
sion and the development of more precise estimates of
bleeding risk in this population.
There are several potential sources of bias within
our study that require comment.
First, this was a post hoc subgroup analysis from a
larger cohort study and, accordingly, we did not col-
lect data on or control for certain relevant factors,
such as the indication for the BT. Similarly, those who
ordered a BT were not masked to the patient’s platelet
count or severity of toxemia; the higher rate of throm-
bocytopenia and preeclampsia among the women who
underwent a BT supports this point. Finally, we did
not assess whether the BT was measured prior to or
during the first stage of labour; a condition of height-
ened anxiety which may slightly augment the BT.1 7
Accordingly, we must interpret our findings with cau-
tion, particularly the apparently high specificity and
PPV of the platelet count for a prolonged BT.
The absence of a normotensive pregnant control
group presents another limitation to our study, espe-
cially given the paucity of literature surrounding BT
variations during uncomplicated pregnancy.2,17 Thus,
our definition of an abnormal BT (i.e., greater or equal
to eight minutes) may have been inappropriately
applied, leading to another source of bias in our esti-
mation of the platelet count-BT test properties. Finally,
in the absence of data on hemorrhagic events in this
population, we cannot draw inferences about the pre-
dictive value of the platelet count for this outcome.
A large prospective cohort study might optimally
determine which risk factors and hematological mark-
ers are important predictors of bleeding risk among
both normotensive and hypertensive pregnant
women. By comparing these women to those with
gestational thrombocytopenia,3 6one may shed further
light on bleeding abnormalities peculiar to women
with preeclampsia. Finally, although spinal hematomas
Lesser
