This policy provides limited coverage for molecular phenotyping of blood
product antigens as part of the pre-transfusion evaluation for patients who
may require or are expected to require a blood product transfusion(s) (Red
Blood Cells [RBCs], Platelets or Leukocytes) when at least one of the
following criteria is met:

  * Long term, frequent transfusions anticipated to prevent the development of alloantibodies (e.g., sickle cell anemia, thalassemia, chronic transfusion dependent hematologic disorders or other reasons); OR
  * Autoantibodies or other serologic reactivity that impedes the exclusion of clinically significant alloantibodies (e.g. autoimmune hemolytic anemia, warm autoantibodies, patient recently transfused with a positive DAT, high-titer low avidity antibodies, patients about to receive or on daratumumab therapy, other reactivity of no apparent cause); OR
  * Suspected antibody against an antigen for which typing sera is not available; OR
  * Laboratory discrepancies on serologic typing (e.g., rare Rh D antigen variants)

Laboratory developed tests (LDTs) that perform molecular phenotyping of blood
product antigens may be considered covered for the same indications if the
test demonstrates validity and clinical utility equivalent to or better than
covered tests as demonstrated in a technical assessment.

Medicare does not expect molecular testing to be performed on patients
undergoing surgical procedures such as bypass or other cardiac procedures, hip
or knee replacements or revisions, or patients with alloantibodies
identifiable by serologic testing that are not expected to require long term
frequent transfusions. The medical necessity for molecular blood product
phenotyping must be documented in the patient's medical record.

Blood product molecular antigen typing tests are considered germline tests and
thus must comply with relevant Medicare or Contractor policies regarding
germline testing.

As molecular genotyping includes a review of many genes that code for cellular
antigens that must be evaluated for proper patient care, single gene tests are
not reasonable and necessary.

If there is a rare instance that a single blood product antigen is reasonable
and necessary, its utility must be appropriately documented in the patient's
medical record for validation by medical review.

For patients who require a blood product transfusion, an important step taken
prior to the transfusion of any blood product is compatibility testing between
the recipient's serum and the blood product being transfused. In addition to
the ABO and Rh system there are 34 other recognized blood group antigen
systems by the International Society of Blood Transfusion.1 Identifying the
blood product antigens to which the transfusion recipient will have an immune
reaction is a critical component of this compatibility testing, though for
most patients identification of ABO and Rh compatibility is sufficient.2
However, for patients who have alloantibodies or patients who have a
predisposition to develop alloimmunization (e.g., patients with sickle cell
disease and others who are chronically transfused), compatibility testing of
additional systems may be needed.2,3 Hemagglutination has traditionally been
the most common serologic method of determining a blood product phenotype. In
this technique, the patient's RBCs are tested with antisera specific for the
antigens of interest.2,4 However, this method has limitations. It requires
direct agglutination typing sera for the antigen, and hemagglutination testing
results are not meaningful if a patient has a positive direct antiglobulin
test (DAT).3,4 In addition, serologic phenotyping is likely to be erroneous in
the transfused patient who may have persistent donor blood products in
circulation, such as patients getting chronic frequent transfusions, and it
has been suggested that chronically transfused patients or patients who have
had a massive transfusion should not receive phenotyping using serological
methods, or that if serological methods are used, they should be confirmed
with molecular techniques.3,5

Because molecular genotyping is not subject to the limitations of conventional
serologic testing, the transfusion community has recognized molecular typing
as a potential tool to aid in the determination of immune compatibility
between donated blood products and the transfusion recipient in a number of
circumstances where conventional methods may not be adequate, such as in
patients who have a positive direct antigen test, in patients who have been
recently transfused or those who are chronically transfused,6 in patients
where a distinction between autoantibodies and alloantibodies is needed, or in
situations where the presence of a weakly reactive anti-body is
suspected.2,3,7,8

Prior to broad clinical availability of molecular genotyping in the United
States, a number of studies demonstrated both the feasibility of this
technique and the incremental information it could provide over serologic
typing in limited clinical contexts.

As early as 1999, a study from Germany in patients receiving chronic
transfusions demonstrated disparate molecular Rh phenotyping in 7 of 27
patients compared to serologic typing.9 Soon afterwards, Reid et al6
demonstrated that Deoxyribonucleic acid (DNA) from blood samples could be used
to genotype patients who had recently been transfused. Castilho et al10
confirmed the unreliability of serologic testing when they showed that 6 of 40
molecular genotypes differed from serologic phenotypes in multiply transfused
sickle cell anemia (SCA) patients10, and in 9 of 10 alloimmunized thalassemic
patients.11 A number of investigators have replicated these findings, most
notably Bakanay et al12 when they demonstrated genotypic and phenotypic
discrepancies in 19 or 37 multi-transfused patients in multiple alleles. The
discrepancies aided in the selection of antigen-matched blood products and
improved RBC survival, ultimately improving patient care. A recent case report
by Wagner5 highlighted the practical utility of molecular testing over
serologic testing for chronically transfused patients.

In a prospective observational study, Klapper et al13 used the HEA BeadChipTM
to provide extended human erythrocyte antigen (xHEA) phenotyped donor units
and recipient patient samples. XHEA-typed units were assigned to pending
transfusion requests using a web-based inventory management system to simulate
blood order processing at four hospital transfusion services. The fraction of
requests filled (FF) in 3 of 4 sites was > 95% when matching for ABO, D and
known alloantibodies, with a FF of > 90% when additional matching for C, c, E,
e, and K antigens. The most challenging requests came from the fourth site
where the FF was 62 and 51% respectively, even with a limited donor pool. A
small prospective observational study by Da Costa et al 14 found that 21 of 35
sickle cell anemia (SCA) patients had discrepancies or mismatches, mainly in
the Rh, Duffy, Jk and MNS blood groups, between the genotype profile and the
serologically-matched blood unit for multiple antigens. These authors report
that their genotype-matching program resulted in elevated hemoglobin levels,
increased time between transfusions and prevented the development of new
alloantibodies.

Two papers showed the feasibility of routinely applying molecular blood
banking techniques in a hospital transfusion service. Routine RBC testing has
been implemented in a large tertiary care hospital in Los Angeles, CA to
maximize efficient use of blood units.15 Patients with warm or cold reacting
autoantibodies, patients with SCA and patients with antibodies that could not
be identified were molecularly genotyped and received molecularly matched
blood from the hospital's genotyped donor inventory. The practical
implementation of molecular erythrocyte antigen typing was described for a
large hospital in Cleveland, OH;16 pre-transfusion molecular typing is
performed on chronically transfused patients, patients with autoantibodies,
multiple antibodies, when no antigen specific antibody is available for
testing and to solve laboratory discrepancies. The authors note that the major
benefit of molecular typing is its application for patients who cannot be
typed by serology due to an unsuitable sample. Valid results can be obtained
even when they have been transfused within a few days of testing or have been
massively transfused. Samples selected for molecular testing were based on an
algorithm.  
  
The emergence of novel medications, particularly monoclonal antibodies, has
also created challenges for serologic phenotyping methods. Two recent research
studies have demonstrated that treatment with daratumumab, a CD38 monoclonal
antibody, can bind to CD38 expressed on the surface of RBCs and interferes
with serologic testing, thereby preventing cross match.17 More recent evidence
suggests that treatment with Hu5F9-G4, an IgG4 monoclonal antibody targeting
CD47 also interferes with pretransfusion testing.18

Numerous prior Medicare coverage decisions have considered the evidence in the
hierarchical framework of Fryback and Thornbury22 where Level 2 addresses
diagnostic accuracy, sensitivity, and specificity of the test; Level 3 focuses
on whether the information produces change in the physician's diagnostic
thinking; Level 4 concerns the effect on the patient management plan and Level
5 measures the effect of the diagnostic information on patient outcomes. To
apply this same hierarchical framework to analyze an in vitro diagnostic test,
we utilized the ACCE Model Process for Evaluating Genetic Tests.23 The
practical value of a diagnostic test can only be assessed by taking into
account subsequent health outcomes. When a proven, well established
association or pathway is available, intermediate health outcomes may also be
considered. For example, if a particular diagnostic test result can be shown
to change patient management and other evidence has demonstrated that those
patient management changes improve health outcomes, then those separate
sources of evidence may be sufficient to demonstrate positive health outcomes
from the diagnostic test.

It has long been recognized that immunohematologic compatibility is critical
to a successful blood product transfusion. It has also long been recognized
that serologic methods of determining compatibility, while useful in many
cases have limitations for particular groups of patients. Molecular methods
for blood product antigen determination are not subject to the same
limitations, and Food and Drug Administration (FDA)-approved tests using
molecular methods have been developed and validated to detect particular
alleles within particular blood group systems. As such, FDA-approved tests are
reasonable and necessary for blood product antigen typing in patients for whom
a transfusion is needed when conventional serologic testing methods are
inadequate or at a high risk of producing unreliable or misleading results.

The evidence reviewed here did not seek to identify laboratory-developed tests
intended to be used for the same purpose. However, since FDA-approved tests to
detect all clinically significant alleles are not available at this time as
the position statement from Association for the Advancement of Blood &
Biotherapies (AABB), America's Blood Centers, and American Red Cross24 notes,
laboratory developed tests (LDTs) remain important to allow for the
identification of unusual alleles unlikely to be readily available on FDA-
approved platforms. LDTs may be considered reasonable and necessary if peer-
reviewed evidence demonstrates that a rigorous validation has been done to
show that they accurately predict/identify the blood product antigens.