Measuring activity of the MCAD enzyme
the diagnosis of MCAD deficiency is suspected some tests can be done to
see what level of activity of the MCAD enzyme can still be detected.
the one hand this can confirm that the MCAD enzyme indeed does not
function (properly) and that we can speak of a deficiency. This
confirms the diagnosis.
On the other hand this test will indicate
how much residual activity of the enzyme is still present and we could
estimate the patients tolerance towards for example fasting. There are
different varieties of MCAD deficiency, serious kinds, but also milder
The test to measure enzymatic activity can be done in 2 kinds of cells: lymphocytes and fibroblasts.
A lymphocyt is a kind of white blood cell. So lymphocytes can be found in a blood sample.
are the most important cells of the connective tissue, and help among
others with the construction of the skin tissue. So fibroblasts can be
found in skin tissue.
test on lymphocytes requires only a blood sample and can be done quite
quickly (a few weeks). So this is the most obvious test to confirm the
diagnosis in a neonate. The
test on fibroblasts requires a skin biopsie. A small piece of the skin
is cut from a not too visible location (eg under the upper arm). Then
these skin cells have to be cultured in a laboratory before the test
can be done. This takes a whole lot longer (a few months or even a
year).Both tests are done in a
similar way, the MCAD enzyme is present in both kinds of cells. In a
specialized laboratory a specific substance (called a substrate) is
added to the cells. This substance is specifically chosen because it
will only react with the MCAD enzyme. By checking to what extend the
enzym can act on this substance, we get an idea of how much residual
activity is present.
Patients with a severe kind of MCAD deficiency have a residual activity of (far) less than 10%
If the residual activity is between 10 and 20 % of normal activity, then the MCAD deficiency is considered to be mild.
Genetic research can be done on the DNA of the patient in order to identify the specific mutation(s).Read further about genetic research >