Sponsors: Centers for Disease Control and Prevention (CDC) and the Association of Public Health Laboratories (APHL).
A major public health responsibility, newborn screening for detection of treatable, inherited metabolic diseases is a system consisting of six parts: education, screening, follow-up, diagnosis, management, and evaluation. Effective screening of newborns using dried-blood-spot (DBS) specimens collected at birth, combined with follow-up diagnostic studies and treatment, helps prevent mental retardation and premature death. These blood specimens are routinely collected from more than 95% of all newborns in the United States; state public health laboratories or their associated laboratories routinely screen DBS specimens for inborn errors of metabolism and other disorders that require intervention. For more than 28 years, the Centers for Disease Control and Prevention (CDC) with its cosponsor, the Association of Public Health Laboratories (APHL), has conducted research on materials development and assisted laboratories with the quality assurance (QA) for these DBS screening tests. All laboratories in the United States that test DBS specimens participate voluntarily in the Newborn Screening Quality Assurance Program (NSQAP). The QA services primarily support newborn screening tests performed by state public health laboratories; however, CDC also accepts other laboratories and international participants into the QA program. CDC provides QC materials, proficiency testing (PT) services, and technical support to 73 domestic screening laboratories, 28 manufacturers of diagnostic products, and 300 laboratories in 53 foreign countries. This program is a comprehensive provider of QA services for newborn screening worldwide.
In 1978, the first DBS materials from CDC were distributed for congenital hypothyroidism screening. Currently, the expanded program includes screening for phenylketonuria, galactosemia, congenital adrenal hyperplasia, homocystinuria, and maple syrup urine disease. In 1991, sickle cell disease and other hemoglobinopathies were added to the QA program after studies showed that pneumococcal sepsis in young children with sickle cell disease was reduced by as much as 84% through early identification and treatment; these studies demonstrated the value of newborn screening for this disease. In 1994, the QA program for the DNA confirmatory methods using DBS specimens for sickle cell diseases was added. In 2001, NSQAP operated a pilot PT program for laboratories testing DBS by tandem mass spectrometry (MS/MS) for detection of amino acid metabolic disorders, fatty acid oxidation disorders, and organic acid metabolic disorders. We brought the MS/MS component into a PT evaluation status in 2002 with the application of cutoff decisions and presumptive classifications for grading. In 2002, we began distributing panels of DBS specimens for immunoreactive trypsinogen (IRT) measurements and in 2003 we added DNA confirmatory testing for cystic fibrosis. In 2005, we began a pilot PT program for Toxoplasma gondii antibodies.
The QC program enables screening laboratories to achieve high levels of technical proficiency and continuity that transcends changes in commercial assay reagents while maintaining the high-volume specimen throughput that is required. The PT program provides laboratories with quarterly panels of blind-coded DBS specimens and gives the laboratory an independent external assessment of its performance. Each year several laboratories misclassify at least one PT specimen and are provided immediate consultation to resolve the analytical problem.
CDC prepares and distributes to national laboratories more than 500,000 DBSs per year. The DBS materials manufactured at CDC must simulate as closely as possible the actual specimens tested. DBS materials for QC and PT are certified for homogeneity, accuracy, stability, and suitability for all assays manufactured by different commercial sources.
Through interactive efforts with state laboratories, NSQAP continues to strive for improvements in services offered and to meet the growing and changing needs for newborn screening in the public health community.
