The Biochemical Genetics Laboratory, established in 1978, was the first such laboratory in the Gulf South and remains the most comprehensive biochemical laboratory in the region. The Biochemical Genetics Laboratory has been the referral laboratory for the Louisiana State Genetics Disease Program for confirmatory analysis of newborn screening in inborn errors of metabolism for over 20 years. Our laboratories are committed to quality and timely performance of testing. The Human Genetics Program is unique in providing the most comprehensive spectrum of genetic services to the medical communities of Louisiana and the Mississippi Gulf Coast. The interpretation of the diagnostic testing is always performed by board-certified Biochemical Genetics specialists. A laboratory test order form can be found at the end of this page.

Quality Assurance
The Biochemical Genetics Diagnosis laboratory is accredited by CAP (College of American Pathologists) and certified by CLIA (Clinical Laboratory Improvement Act 1988), and regularly participates in the National Tay-Sachs Disease proficiency testing program. The laboratories participate in regular internal and external quality assurance programs, including sample exchanges and proficiency testing.

Skilled Analysis and Cost-Effective Results
The clinical staff of the Human Genetics Program is available for telephone consultation regarding utilization of the services provided by our facility. Assistance in choosing the proper test, questions about appropriate specimens, testing procedures, and the interpretation of results, is available. Our faculty and staff can help you choose the best, most cost-effective test or tests, sometimes avoiding unnecessary, inappropriate, or repetitive testing. The Human Genetics telephone number is 504-988-5229; hours are 8:30 am to 5:00 PM Central Time. After hours, Biochemical Genetics Paging is available at 504-501-6011.

Urgent Contact
The services of the Human Genetics Program Diagnostic Laboratories are available 24 hours a day, 7 days per week. A staff member is always available on-call for urgent physician consultations and lab analyses on pager 504-501-6011.

Metabolic studies are indicated in patients suspected of having inborn errors of amino acid metabolism, urea cycle defects, inborn errors of organic acid metabolism, and in patients suspected of mitochondrial or peroxisomal dysfunctions.

One of the major problems facing the physician in attempting to diagnose an inborn error of metabolism is the lack of a specific phenotypic presentation because of clinical variability. Patients will usually be referred for evaluation with one of the following presentations: infants admitted to "rule-out sepsis", infants or children presenting with failure to thrive, developmental delay, mental retardation, or seizures, and sudden infant death syndrome (SIDS). School-age children with loss of developmental milestones (regression) may be tested for a broad spectrum of neurodegenrative disorders. Additionally, children with unusual stature who may have a skeletal dysplasia may be evaluated for metabolic causes of inherited bone disease.

A. Quantitative Amino Acids
Approximately forty ninhydrin reactive compounds including all physiological amino acids are quantitated in physiological fluids in our laboratory (plasma amino acids, urine amino acids, plasma phenylalanine and tyrosine only, and cerebrospinal fluid amino acids). Automated high performance liquid column chromatography methodology is used.

B. Quantitative Organic Acids
Approximately 200 organic acids of interest in human metabolism are searched for and quantitated by gas chromatography/mass spectrophotometry. Organic acids are performed in our laboratory on urine specimens.

C. Carnitine and Acyl Carnitine
L-carnitine is essential for the transport of fatty acids across the mitochondrial membranes. As part of the diagnostic work-up of patients with inborn errors of organic acid metabolism (or in patients with idiopathic cardiomyopathy suspected of having primary carnitine defiency), free carnitine and acylcarnitine can be evaluated in both plasma and urine. Carnitine supplementation in these patients often leads to remarkable clinical improvement.

D. Urine Thin Layer Chromatographies
Although these are qualitative and not quantitative procedures, the expertise generated in our lab over the past 20 years makes them invaluable screening assays for these three groups of disorders.

1. Thin Layer Chromatography for Mucopolysaccharides
Mucopolysaccharides spot test is performed initially on all urine specimens sent for MPS chromatography. If the spot test is positive, a thin layer chromatography is performed. This enables a distinct separation of the abnormal mucopolysaccharides in the urine (dermatan, heparan, and keratan sulfate) from chondroitin sulfate that can be found in some control urines.

2. Thin Layer Chromatography for Oligosaccharides
This diagnostic procedure is recommended for patients suspected of having sialidosis, fucosidosis, or mannosidosis.

3. Thin Layer Chromatography for Mono and Di-Sugars
This assay is performed in our lab to identify mono and di-sugars in the urine of patients suspected of having galactosuria, lactosuria, fructosuria, etc. The sugar can be identified in the urine only if the patient's dietary intake includes the sugar. It is important to remember that if the sugar was eliminated from the diet, it cannot be detected in the urine.

E. Enzyme Studies These assays were designed to confirm or rule-out the deficient or decreased activity of a specific enzyme leading to the inherited disorder. For many of the assays, the carrier state for this enzyme defect can also be determined. The enzyme activity can also be assayed in various tissues, but the most commonly used are: serum, peripheral blood white cells, cultured fibroblasts, and for prenatal diagnosis (available for some assays, please contact the laboratory), amniocytes. The assays are performed using either spectrophotometric or fluormetric synthetic substrates or with radioisotope labeled substrates using the natural substrate.

1. Lysosomal Enzyme Studies This is a large group of lysosomal enzymes in which a deficient or decreased activity of the specific enzyme leads to lysosomal storage disorder. Clinically, they are all characterized by physical and/or neurological regression in an individual that was apparently healthy. The age of onset varies from early infancy to late adulthood. In all of the lysosomal storage disorders, multiple tissue or organ involvement is apparent. The three major groups within this entity are the sphingolipidosis, mucopolysaccharidosis, and mucolipidosis. The assays are performed on either serum, white blood cells, fibroblast tissue, and amniocytes.

2. Serum Biotinidase Biotinidase deficiency was described as a distinct clinical entity several years ago. Since then, many new patients with this disorder have been detected, including several in Louisiana. Recently biotinidase screening has been added to the newborn screening programs in several sates. The presenting symptoms can include one or more of the following: seizures, failure to thrive, skin rashes, alopecia, and hearing loss. As this inherited disorder is ammendable to a simple treatment by supplementing biotin, it is important to evaluate biotinidase activity in all patients suspected of having this disorder.

3. Galactose-1-Phosphate Uridyltransferase The measurement of galactose-1-phosphate uridyltransferase activity in red blood cells is essential for the diagnosis of galactosemia in newborns. This diagnostic test is indicated whenever the possibility of galactosemia is considered. The activity of the enzyme in the red cells is assayed on whole blood.

Please contact the department for sample specifications before shipping. To view the lab form and all tests, please open the Lab Test Form.