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Klinisk Biokemi i Norden · 2 2019
Hemolysis interference studies – the method used
in the preparation of hemolyzed samples has
impact on the test results
Gro Gidske
1
, Una Ørvim Sølvik
2
, Sverre Sandberg
1
, Gunn Berit Berge Kristensen
1
1
Norwegian Organization for Quality Improvement of Laboratory Examinations (Noklus)
2
Department of Global Public Health and Primary Care, Faculty of Medicine, University of Bergen
What is known on this topic?
• There is limited knowledge if the method used for
preparation of hemolyzed samples for interference
studies can affect the test results.
• Studies have shown that interference caused by hemo-
lysis on ammonia measurement depends on the met-
hod used in the preparation of hemolyzed samples.
What this paper adds
• This is the first study that compares three different
methods often used in the preparation of hemoly-
zed samples in interference studies:
Osmotic shock-,
Freeze-
and
Shear
methods.
• The same degree of hemolysis affects the measure-
ments of several measurands differently, especially
lactate dehydrogenase (LDH), depending on the
method used in the preparation of the hemolysate.
• For the Shear method, there was a considerable
between-donor difference in hemoglobin concen-
trations after aspiration of whole blood through a
thin needle.
What we recommend
• We recommend that the
Freeze
method, which
is practical and easy to perform, should be used
in the preparation of hemolysate since it includes
lysis of leukocytes, platelets and erythrocytes, and
therefore best mimics the hemolysis that may occur
in patient samples.
Hemolysis in blood samples is a major challenge in
medical laboratories, and the most common reason
for sample rejection (1). How, and to what extent,
hemolysis may affect test results, depends on the
measured analyte and the measurement principle
of the instrument used. Most instruments used in
clinical chemistry laboratories today can measure the
amount of hemolysis, i.e. free hemoglobin (Hb), pre-
sent in each patient sample and transfer the result to
the laboratory information system (LIS). Thereby test
results can automatically be rejected or commented
upon at predefined Hb cut-off points (2).
Interference studies are performed to establish
instrument specific cut-off points for when a test
result should be rejected or commented upon due to
hemolysis. Cut-off points are commonly recommen-
ded by the manufacturers of in vitro diagnostic (IVD)
analytical systems. If laboratories use these cut-off
points, they should verify their intended usefulness,
strengths and limitations (3). Verification may be
challenging since manufacturers’ package inserts
often lack information about experiment design and
how cut-off points were defined (2, 4, 5). Discrepan-
cies between manufacturers’ Hb cut-off points and
cut-off points from local interference studies have
been observed (5-7). This could be due to differences
in acceptance criteria or the methods used in the pre-
paration of hemolyzed samples for testing.
Some define in vitro hemolysis as the abnormal
breakdown of erythrocytes (2), while others define
hemolysis as the abnormal breakdown of eryth-
rocytes, leukocytes and platelets (8). The different
definitions of hemolysis in various publications may
explain why hemolyzed samples are prepared diffe-
rently. The methods often used in the preparation of
hemolyzed samples in interference studies are (9): 1)
