ADLM 2025 Special Edition Summer Newsletter - Flipbook - Page 11
Summer 2025
b) Reagents and controls required for the FVIII assay
•
APTT reagents – the same reagents that are used for
baseline APTT testing are required for the intrinsic
pathway clotting factor, namely the APTT reagent (Actin
FS™) and calcium chloride.
•
Reference plasma – this reference plasma (Standard
Human Plasma™), which contains a known amount of
FVIII, is used to generate a standard curve (calibration
curve) against which the clotting time of the patient
sample is compared and converted into an absolute value
(%).
•
Factor VIII de昀椀cient plasma – this plasma contains normal
amounts of all coagulation factors but is completely
de昀椀cient in FVIII.
•
Normal and abnormal controls – Control Plasma N™ and
Control Plasma P™
c) Automated FVIII analysis on Sysmex analyzers
Individual clotting factor assays can be performed on select
Sysmex coagulation analyzers. The analyzer needs to be
calibrated using Standard Human Plasma whenever the lot
number of reagents changes. Please refer to the instructions
for use or consult your local Sysmex representative.
d) Results interpretation
The FVIII results are reported as a percentage value. The
normal reference range can be quite wide (~50 – 150%) but
this is not relevant for the diagnosis of hemophilia. A diagnosis
of hemophilia requires there to be an isolated FVIII level below
30% in a male patient. The level of factor will determine the
clinical severity and, consequently, the approach to treatment.
What is the role of the laboratory in hemophilia care?
Not only are factor assays essential to con昀椀rm the diagnosis
of hemophilia, but testing is also an essential component of
on-going hemophilia care. Hemophiliacs bleed because they
have a partial or complete absence of a single clotting factor;
namely FVIII or FIX; therefore, the main treatment for bleeding
episodes is to replace the missing clotting factor. In order for
hemostasis to be effectively restored, clotting factor levels
must reach a certain minimum level. It is therefore vital that
factor levels are checked at speci昀椀c time intervals after the
factor concentrate has been administered. Algorithms exist
which assist in determining how many units of FVIII for FIX
need to be infused based on the patient’s factor level and
the body weight. This is used to determine the starting dose
of factor concentrate, but the response to treatment must
be con昀椀rmed by repeating the factor assay post-infusion. If
the recovery of the factor level is sub-optimal, then a top up
dose must be given, especially if there are still clinical signs
of bleeding. If patients do not respond as expected or require
ever increasing doses to control bleeding in comparison to
previously, the possibility that inhibitors have developed must
be explored.
What are inhibitors?
One of the most serious complications that arise from
hemophilia treatment is the development of antibodies, or
inhibitors, against the infused factor concentrate. This tends
to occur only in patients with severe hemophilia where there
is less than 1% or a complete absence of factor. Because the
patient has virtually no endogenous FVIII (or FIX), any infused
exogenous factor is seen by the body as a foreign substance
against which antibodies are produced. These antibodies are
referred to as inhibitors as they bind to the infused factor and
prevent it from participating in the coagulation cascade. This
means that larger quantities of infused factor are required to
sustain coagulation. This occurs in approximately 5 to 10%
of patients with severe hemophilia A and 2 to 4% in patients
with severe hemophilia B.
Sysmex Testing Solutions
Hemophilia patients are at risk of bleeding (internally and
externally) due to reduced/absent functional factor VIII or
IX in their blood. While proper diagnosis of hemophilia is
crucial, management of hemophilia is equally important,
since this is a life-long disorder.
The testing for diagnosis of hemophilia A and treatment
monitoring of hemophilia A generally differ. Laboratories
utilizing Sysmex CS-Series and CN-Series analyzers*
have access to industry-leading reagents and advanced
technology to provide the accurate results required for the
management of these patients.
One-stage Factor VIII assay (primarily used in
diagnostic testing)
•
Requires the following reagent products (sold
separately):
•
•
•
Factor VIII de昀椀cient plasma
Actin FS or Actin FSL – APTT reagent
Calcium chloride
•
Owren’s Veronal Buffer (OVB) – for automatic sample
dilutions performed by the analyzer
•
Standard Human Plasma (SHP) – for calibration curve
generation
•
Control N - Normal level QC
•
Control P - Abnormal level QC
Factor VIII Chromogenic assay (primarily used in
management testing)
•
Requires the following reagent products (sold
separately):
•
Factor VIII Chromogenic kit
•
OVB – for automatic sample dilutions performed by the
analyzer
SHP – for calibration curve generation
Control N - Normal level QC
Control P - Abnormal level QC
•
•
•
*Analyzers not available in all markets.
NEWS |
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