Age of Blood in Sickle Cell Transfusion

The Investigators assembled a multidisciplinary investigative team to examine the potential
effects of older red cell units in adults with Sickle Cell Disease(SCD). Study staff have
preliminary data that show: 1) there is equipoise among blood bank directors about the
effects of older units in adults with SCD, 2) in our institution, many adults are
administered older units, 3) older units activate macrophages and 4) this physiology promoted
by older units is associated with an increased risk of infection. Our team is now poised to
take the next investigative step: a prospective, randomized study.

In Milwaukee, 1/3 of units transfused to adults with SCD are >30 days old, but nation-wide
some restrict the transfusion of older units. About four hundred adults receive care in the
Adult Sickle Cell Clinic at Froedtert Hospital in Milwaukee, about 23 of who receive chronic
outpatient transfusions for chronic pain or stroke prophylaxis. Transfusions are administered
to adults regardless of storage age, except in the case of red cell exchange, for which there
is a policy to use less than 14 day old units. In a 3-year retrospective review of
transfusions administered to adults with SCD, 627 units were given via simple transfusion
over 281 outpatient encounters. The overall median unit storage age was 22 days (range: 2-42
days), and 25% of the units transfused were stored 33 days or longer.

To determine the opinions and policies of other hospital blood bank directors about the use
of older red cell units for patients with SCD, study staff conducted a nation-wide survey
(n=90). While only 23% of respondents had a storage age restriction policy for patients with
SCD, 31% thought that older units were not as effective as younger units, and 65% believed
that evidence-based policies were needed

Adults with SCD may be susceptible to the effects of an older unit's physiology because they
are prone to infection, inflamed, and poorly equipped to handle excess iron. In a cohort of
40 steady-state adults with SCD, we specifically measured markers of inflammation and iron
excess. High sensitivity C-reactive protein, a marker of systemic inflammation, was found to
be markedly elevated (median 5.6 mg/L, range 0.4-60 mg/L; reference range <1.0 mg/L), as was
ferritin, a marker of iron stores (median 2,969 ng/ml, range 20-12,300 ng/ml; reference range
13-400 ng/ml).

Forty chronically-transfused adults with SCD will be randomized in a double-blind fashion to
receive ≥30 day-old or ≤10 day-old units for 3 months. Subjects will be randomized in blocks
of 5 and stratified by age: at least 10 subjects from each of the age ranges 18-30 and 31-45
years will be enrolled. Pre-transfusion, sterile samples will be extracted from red cell
units. Patient peripheral blood will be also obtained 1 month before randomization,
immediately pre-transfusion, and 2 and 24 hours post-transfusion. Hemoglobin will be measured
pre-transfusion, 2 and 24 hours post-transfusion, and 2 weeks post transfusion. Participants
will complete standardized diaries daily to document symptoms of infection, SCD pain,
medications and Emergency Department(ED) or hospital use. Diaries will be collected and
participants will be assessed with each transfusion encounter and 4 weeks after the last
transfusion. To ensure compliance, coordinators will contact subjects weekly to complete the
diaries.

Study staff will evaluate red cells pre- and post-transfusion for Phosphatidylserine(PE),
Phosphatidylethanolamine(PS), and microparticles as above for all blood samples. White cells
will be isolated with established separation techniques. The white cell populations of
interest will be defined by their location on a forward scatter/side scatter plot and their
positivity using key fluorochrome-labeled identity markers (macrophages: CD14, neutrophils:
CD16). Once the cell populations of interest are identified, the cells will be evaluated for
various markers of activation. The plasma fraction from each patient and red cell unit will
be diverted to determine concentrations of free heme/hemoglobin, cytokines, and NTBI,
respectively.

Inclusion Criteria:

1. age 18 to 45 years

2. Hemoglobin SS/Hemoglobin Sβ-thalassemia0

3. on chronic red cell transfusion therapy

4. outpatient at the time of transfusion

Exclusion criteria:

1. history of reactions to transfusion therapy that cannot be adequately managed by
antihistamines

2. ≥2 red cell alloantibodies

3. participation in another therapeutic trial for SCD

4. pregnant

5. HIV positive

6. uncontrolled inter-current illness, or psychiatric illness/social situations that
would limit compliance with study requirements.