HOW IS BIOTINIDASE DEFICIENCY DETECTED?

There are three ways doctors may suspect a diagnosis of biotinidase deficiency. An infant may be identified by newborn screening before symptoms develop, an infant or child may develop symptoms that lead to the diagnosis, or if there has been a previous affected child in the family, the diagnosis can be made prenatally. Prenatal diagnosis is discussed in a later section. Doctors then confirm the diagnosis of biotinidase deficiency by measuring the activity of biotinidase in serum.

Newborn Screening
All 50 states in the United States and many other countries have newborn screening programs. Through these programs, all babies born within the state or country are tested for specific disorders such as phenylketonuria (PKU) and hypothyroidism. Early diagnosis of these conditions allows doctors to treat babies before they become sick.

Newborn screening for biotinidase deficiency began in Virginia in 1984 and is now performed in many other states and countries. Not all screening programs include testing for biotinidase deficiency. Currently, about one half of the states and provinces in the U.S. and Canada screen for this condition. In addition, many countries are also screening all or some of their newborns for biotinidase deficiency.

How was my baby screened?
The heels of infants are pricked soon after birth, usually just before they go home from the hospital. The blood is spotted on filter paper cards, dried, and sent to a newborn screening laboratory for testing. The dried blood from just one card can be used to screen a baby for several different diseases. To screen for biotinidase deficiency, the activity of biotinidase in the dried blood is measured. Abnormal test results are repeated and confirmed by measuring biotinidase activity in serum or plasma of a fresh blood sample. Usually the cost of testing is paid by the newborn screening program, and parents often do not even realize that their baby was screened unless the results are abnormal.

If your child was detected through newborn screening, the diagnosis was made quickly, probably before any symptoms developed.

Clinical Diagnosis
If your child was not screened for biotinidase deficiency at birth, your child was probably diagnosed after some of the clinical symptoms of biotinidase deficiency appeared. Children diagnosed in this way may have had medical problems for some time before doctors suspected the correct cause. Some children are even diagnosed as having other disorders because many of the symptoms of biotinidase deficiency can resemble those produced by other conditions. But once biotinidase deficiency is suspected, a blood sample is sent to a laboratory to measure the activity of biotinidase. Fortunately, once the correct diagnosis is made, most of the symptoms improve or disappear with treatment.