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Biotinidase deficiency

Biotinidase deficiency is an inherited disorder in which the body is not able to process the vitamin biotin properly. Biotin, sometimes called vitamin H, is an important water-soluble vitamin that aids in the metabolism of fats, carbohydrates and proteins. more...

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Approximately 1 in 60,000 newborns are affected by profound (less than 10 percent of normal enzyme activity) or partial (10-30 percent of normal enzyme activity) biotinidase deficiency.


Mutations in the BTD gene cause biotinidase deficiency. Biotinidase is the enzyme that is made by the BTD gene. Many mutations that cause the enzyme to be nonfunctional or to be made at extremely low levels have been identified. Biotin is a vitamin that is chemically bound to proteins. (Most vitamins are only loosely associated with proteins.) Without biotinidase activity, the vitamin biotin cannot be separated from foods and therefore cannot be used by the body. Another function of the biotinidase enzyme is to recycle biotin from enzymes that are important in metabolism (processing of substances in cells). When biotin is lacking, specific enzymes called carboxylases cannot process proteins, fats, or carbohydrates. Individuals lacking biotinidase activity can still have normal carboxylases if they ingest small amounts of biotin.

This condition is inherited in an autosomal recessive pattern, which means two copies of the gene in each cell must be altered for a person to be affected by the disorder. Most often, the parents of a child with an autosomal recessive disorder are not affected but are carriers of one copy of the altered gene.


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Updating newborn screening standards - Brief Article
From Medical Laboratory Observer, 1/1/01 by Judith Nugent

One tiny spot of blood pricked from a baby's heel hours after birth provides enough material to test for 30 life-threatening or severely disabling congenital disorders. But which tests are given depends on where that baby was born. While all states screen for phenylketonuria (PKU) and congenital hypothyroidism and most test for galactosemia and sickle cell disease, the March of Dimes would add 4 more tests to establish a "core group of screening tests" that every baby should receive. Of these 8 tests, it is currently up to state public health agencies whether they also screen for maple syrup urine disease, homocystinuria, biotinidase deficiency, and congenital adrenal hyperplasia. Many pediatric specialists would also test for MCAD and congenital toxoplasmosis.

Since the early 1960s, when Dr. Robert Guthrie developed the first newborn screening test for PKU, there have been efforts to create screening system guidelines. Most screening responsibilities have been shouldered by state public health agencies whose policies were influenced by political, cultural, economic, and technological factors. The variable nature of the state systems made uniform standards for newborn testing an erratic venture at best.

Most recently, the Maternal and Child Health Bureau of the Health Resources Services Administration requested that the American Academy of Pediatrics "review issues and challenges for state newborn screening systems." After drawing on the expertise of bioethicists, parents, researchers, pediatricians, and other healthcare personnel in public and private agencies and institutions, the Newborn Screening Task Force convened in May 1999 in Washington, DC, and developed a series of recommendations, which were published in the August 2000 issue of Pediatrics (vol. 106, no. 2). The report recommends a national model for newborn screening and outlines the criteria, guidelines, and goals for structuring all aspects of a screening program, including testing, diagnosis, referral, followup, treatment, and data management.

Criteria and costs. The goal for newborn screening is to provide early identification of conditions that have side effects that can be prevented or lessened with early treatment. Although the Task Force did not specify which tests should be part of a national model, they did recommend criteria for determining which conditions should be included in a newborn screening program. Inclusion requires that the disorder is serious, that it occurs frequently enough to justify widespread screening, that early diagnosis will benefit the child, and that treatment is available. The test must be simple, safe, and accepted by healthcare professionals, and its validity and utility must meet assurance standards. Issues concerning mandatory versus voluntary testing, informed consent, parental and community education, funding sources, and the use of blood specimens and data are addressed as well.

According to Dr. Edwin Naylor at Neo Gen Screening, Inc., a private screening laboratory in Bridgeville, PA, there are 30 rare but disabling metabolic disorders that "recent developments in technology make it possible and affordable to screen for" today. Tandem mass spectrometry and other technologies can accurately detect these conditions quickly and accurately, if used in a population-based screening system where millions of samples are collected per year.

However, the real cost is in follow-up, according to Jane Adrian, laboratory director at Lincoln Developmental Center, illinois Department of Human Services, which serves people with severe mental and neurologic disabilities. "With tandem mass spectrometry, the cost for expanded screening may come to only $25 a child. But we can't give physicians and families this information and then leave them on their own. A state must decide from a public health perspective whether they want to make the necessary investment in follow-up services.

"At our facility," continues Adrian, "I see people with irreparable mental, neurological, and physical disabilities caused by conditions that could have been treated if diagnosed soon after birth. Although early treatment and long-term management may involve special diets or medications that can prevent or reduce the risk of serious problems, some states and insurance companies are not prepared to absorb the cost of managing these diseases."

QA. If states hope to use the best tests available, state public health agencies must develop and evaluate new testing technologies and set standards for sample and storage collection, lab quality, and information management. To maintain high performance standards, labs must test a sufficient volume of samples annually and must have special expertise in dried blood technology. The Newborn Screening Quality Assurance Program, a collaboration of the CDC and HRSA, have helped labs meet the CLIA QA requirements for test accuracy. With emerging screening technologies such as DNA testing, labs will need to address increased demands on their regulatory and research functions.

COPYRIGHT 2001 Nelson Publishing
COPYRIGHT 2001 Gale Group

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