|
LIST OF BIOCHEMICAL TESTS OFFERED:
|
|
|
BIOTINIDASE
(SERUM) |
This enzyme assay is carried out in serum and is used for the detection of biotinidase
deficiency. Carriers for this disorder can be identified through family studies.
|
|
GALACTOKINASE
(BLOOD) |
The test is used to rule out galactokinase deficiency, a very rare
disorder of galactose metabolism. The major clinical presentation is cataracts. The enzyme is very
unstable. Therefore, it is very important to adhere to sample preparation instructions. The test
method is radiochemical. Carriers can be identified by family studies. If the test includes blood
galactose determinations, provided the newborn has been on lactose-containing formula or breast
feedings, affected newborns can be suspected by newborn screening procedures (NBS). |
|
GALACTOSE
(PLASMA & URINE) |
The galactose level is determined by an enzymatic method. Elevated
levels can be suggestive of abnormalities in galactose metabolism or liver disease. |
|
GALACTOSE-1-PHOSPHATE
(RBC) |
An enzyme coupling method is used to determine the level of
galactose-1-phosphate in red blood cells. High levels are found in new patients diagnosed with
galactose-1-phosphate uridyltransferase deficiency (galactosemia) or UDPgalactose-4-epimerase
deficiency. Often newborns that are Duarte-galactosemia compound heterozygotes (DG) and are on
lactose-containing diets have high values. The test is used for monitoring dietary management of
these patients. |
|
GALACTOSE-1-PHOSPHATE
URIDYLTRANSFERASE
(BLOOD) |
We perform both quantitative and electrophoretic analyses for the
enzyme in red blood cell hemolysates. The quantitative assay is based on a radiochemical method
using C14-labeled galactose-1-phosphate. Labeled product, UDPGal-C14, is separated from labeled
galactose-1-phosphate by ion exchange paper chromatography. Agarose electrophoresis is employed to
resolve Duarte and Los Angeles variants from normal. The combined activity and electrophoretic
pattern determine whether the patient is affected or a carrier of galactosemia. These assays are
used to confirm the diagnosis of galactosemia in patients identified through the NBS programs.
Galactosemic patients usually present with failure to thrive, susceptibility to infection,
hepatomegaly, jaundice, mental retardation, and cataracts. Laboratory findings include galactosuria,
proteinuria and amino aciduria. |
|
|
L-LACTATE/PYRUVATE
(BLOOD & CSF) |
Lactate and pyruvate are determined by an enzymatic method utilizing
the COBAS MIRA chemistry analyzer. Since lactate is continually produced in stored specimen, blood
sample preparation must be handled with great care. Samples
must be prepared according to instructions. An elevated ratio of lactate/pyruvate usually
suggestive of a mitochondrial disturbance. Elevated lactate and pyruvate are found in
patients with pyruvate dehydrogenase deficiency. Elevated lactate is found in other diseases
such as glycogen storage disease type 1, pyruvate carboxylase deficiency, fructose-1,
6-diphosphatase deficiency, and severely ill patients with organic acidemias. Elevated lactate is
also found in patients without a metabolic disorder such as hypoxia. |
|
LYSOSOMAL STORAGE
DISEASE SCREENING
(PLASMA & URINE REQUIRED) |
The objective of this test is to diagnose patients with lysosomal storage disease accompanied by
one or more of the following clinical features: mental retardation, coarse facies, skeletal
abnormalities, short stature, progressive neurodegeneration, cherry red spot, cloudy cornea, and
organomegaly. The test requires both plasma and urine specimen. The following assays are
performed:
- Urine glycosaminoglycan analysis by thin layer chromatography (TLC) and cellulose acetate
electrophoresis.
- Urine oligosaccharide analysis by TLC.
- Urine arylsulfatase A assay.
- Plasma B-Hexosaminidase A assay.
- Plasma B-glucuronidase assay.
The combined studies will diagnose all known types of mucopolysaccharidoses, GM 1 Gangliosidosis,
Alpha-fucosidosis, Alpha-mannosidosis, Sialidosis, Galactosidosis, Mucolipidosis II & III, GM 2
gangliosidosis and Metachromatic leukodystrophy. However, we can not diagnose Krabbe, Gaucher, Fabry,
Niemann-Pick, Farber, B-mannosidosis and Sialic acid storage disease.
|
|
GLYCOSAMINOGLYCANS
(URINE) |
We perform qualitative analyses by TLC and cellulose acetate
electrophoresis of isolated mucopolysaccharides by cetylpyridinium chloride precipitation. The
testing procedures identify abnormally high levels of dermatan sulfate, heparan sulfate and keratan
sulfate in addition to normal chondroitin A/C sulfates. The pattern suggests whether the patient is
affected with Hurler, Scheie, Hunter, Sanfilippo, Maroteaux-Lamy or Morquio syndromes. |
|
OLIGOSACCHARIDES
(URINE) |
Oligosaccharides result from glycoprotein degradation and are excreted
into urine. Characteristic patterns are observed in patients with metabolic abnormality of these
substances. The oligosaccharide pattern is analyzed using TLC & compared to specific patterns
seen in known lysosomal storage disease. The test can rule out Mucolipidosis I, II, III, GM 1
gangliosidosis, Alpha-fucosidosis, and Alpha-mannosidosis. |
|
ARYLSULFATASE A
(URINE) |
The arylsulfatase A test will detect metachromatic leukodystrophy by
measuring enzyme activity at three different pH ranges after dialysis. The combination of low
activity and an abnormal pH activity pattern confirms the diagnosis. |
|
BETA-GLUCURONIDASE
(PLASMA) |
This enzyme assay is performed on plasma and is used for diagnosis of B-glucuronidase
deficiency (MPS VII). Extremely high enzyme activity (> 10 x normal) can be found in patients
with mucolipidosis II & III. |
|
BETA-HEXOSAMINIDASE A
(PLASMA) |
This enzyme assay is performed on plasma and is for the diagnosis of
Tay-Sachs or Sandhoff disease. The substrate used is
4-methylumbelliferyl-2-acetamido-2-deoxy-B-D-glucopyranosyl-6-sulfate. Whenever a very low enzyme
activity is detected, unsulfated substrate is used to differentiate the diagnosis between Tay-Sachs
and Sandhoff disease. Extremely high enzyme activity (> 10 x normal) can be found in patients
with mucolipidosis II & III. |
|
UDPGALACTOSE-4'-EPIMERASE DEFICIENCY
(RBC) |
The enzyme assay is based on coupling reaction. The substrate used is
UDPgalactose. The product formed, UDPglucose, is converted to UDPglucuronic acid by UDPglucose
dehydrogenase changing NAD to NADH. NADH is quantitated by fluorometry. The enzyme is very unstable,
therefore, it is very important to adhere to sample preparation instructions.
There are two forms of epimerase deficiency. One is clinically severe and the symptoms are similar
to classical galactosemia and the other is clinically benign. The severe form of epimerase
deficiency is rare and the enzyme deficiency occurs in all tissues. In the benign form, the enzyme
deficiency appears to be confined to RBC & WBC's. This condition is relatively common among
African Americans. Elevated blood galactose-1-phosphate is usually found in affected patients and
detected by newborn screenings. |
|
| |
|
