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Test for Newborns Detects Blood Disorder

Screening Technique Identifies Life-Threatening T-Cell Lymphopenia

By Jennifer Warner
WebMD Health News

Reviewed by Louise Chang, MD

Dec. 8, 2009 -- An inexpensive new newborn screening method can detect a rare blood disorder that affects the immune system and causes life-threatening complications if left untreated.

A new study shows testing of newborn DNA extracted from dried blood spots on newborn blood screening cards was able to identify infants with T-cell lymphopenia, which is an abnormally low level of vital infection-fighting white blood cells. Infants with T-cell lymphopenia may appear normal at birth and have no family history of immune disorders.

"Consequently, many infants with severe T-cell deficiencies are not identified until life-threatening infections occur," write researcher John M. Routes, MD, of the Medical College of Wisconsin and Children's Research Institute in Milwaukee, in The Journal of the American Medical Association.

Researchers say this is an important issue because early diagnosis and treatment of T-cell lymphopenia can dramatically improve the long-term health of the child. In addition, some childhood vaccines given in early infancy may cause serious infection in children with T-cell lymphopenia.

In the study, researchers looked at whether determining the number of T-cell receptor excision circles (TREC) using DNA from dried blood spots on newborn blood screening cards could detect the disorder in infants in a statewide screening program.

Researchers screened 71,000 infants born in 2008 in Wisconsin using the TREC method. Seventeen full-term infants had at least one abnormal TREC result, 11 of whom had samples further analyzed to detect the number of T cells. Eight of those infants were diagnosed with T-cell lymphopenia.

The cost of the test was about $5.50, and researchers say the number of cases detected by the newborn screening exceeds the required incidence of disease to institute screening.

They say these results support state screening for T-cell lymphopenia, although a formal cost-effectiveness analysis is needed.

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