Gary L. Hoffman

Development of a routine newborn screening protocol for severe combined immunodeficiency

BACKGROUND Severe combined immunodeficiency (SCID) is characterized by the absence of functional T cells and B cells. Without early diagnosis and treatment, infants with SCID die from severe infections within the first year of life. OBJECTIVE To determined the feasibility of detecting SCID in newborns by quantitating T-cell receptor excision circles (TRECs) from dried blood spots (DBSs) on newborn screening (NBS) cards. METHODS DNA was extracted from DBSs on deidentified NBS cards, and real-time quantitative PCR (RT-qPCR) was used to determine the number of TRECs. Positive controls consisted of DBS from a 1-week-old T(-)B(-)NK(+) patient with SCID and whole blood specimens selectively depleted of naive T cells. RESULTS The mean and median numbers of TRECs from 5766 deidentified DBSs were 827 and 708, respectively, per 3.2-mm punch ( approximately 3 muL whole blood). Ten samples failed to amplify TRECs on initial analysis; all but 1 demonstrated normal TRECs and beta-actin amplification on retesting. No TRECs were detected in either the SCID or naive T-cell-depleted samples, despite the presence of normal levels of beta-actin. CONCLUSIONS The use of RT-qPCR to quantitate TRECs from DNA extracted from newborn DBSs is a highly sensitive and specific screening test for SCID. This assay is currently being used in Wisconsin for routine screening infants for SCID.

Improved precision of newborn screening for congenital adrenal hyperplasia using weight-adjusted criteria for 17-hydroxyprogesterone levels

OBJECTIVE To evaluate the efficacy and efficiency of weight-adjusted threshold levels for 17-hydroxyprogesterone (17-OHP) in screening newborn infants for 21 hydroxylase deficiency-congenital adrenal hyperplasia (21-OH-D-CAH). DESIGN Analysis of the number of false-positive reports and diagnoses in infants, of 21-OH-D-CAH with the use of two strategies. Before October 1993, separate criteria for definite abnormal 17-OHP levels were established and implemented for 41,846 infants on the basis of birth weight: either less than 2200 gm (17-OHP level, 90 ng/ml) or 2200 gm or more (40 ng/ml). To reduce the burden of follow-up testing in low birth weight infants, criteria for definite abnormal 17-OHP results were statistically determined for four, rather than two, birth weight divisions: 1299 gm or less (17-OHP level > or = 165 ng/ml), 1300 to 1600 gm (> or = 135 ng/ml), 1700 to 2200 gm (> or = 90 ng/ml), and more than 2200 gm (> or = 40 ng/ml). These criteria were applied to the next 149,684 infants screened, and rates of false-positive test results and of false-positive diagnoses of 21-OH-D-CAH were compared. RESULTS Before implementation of four-tiered weight-adjusted 17-OHP criteria, 205 definite abnormal reports yielded four confirmed cases of 21-OH-D-CAH (positive predictive value = 2%; incidence of 21-OH-D-CAH = 1 in 10,461). With the revised criteria, 61 of 149,684 infants had definite abnormal results and 14 cases of 21-OH-D-CAH were confirmed (positive predictive value, 20%; incidence of 21-OH-D-CAH, 1 in 10,692). No undetected severe cases of 21-OH-D-CAH have been subsequently reported. CONCLUSIONS Weight-adjusted criteria for 17-OHP levels in screening for 21 -OH-D-CAH markedly reduced the number of false-positive results requiring immediate follow-up testing, particularly among low birth weight infants. Increased specificity afforded by these criteria was not accompanied by diminished sensitivity in detecting severe cases. Long-term follow-up of this screened cohort will determine whether the goals of newborn screening for 21-OH-D-CAH are adequately and efficiently fulfilled by this approach.

Guidelines for Implementation of Cystic Fibrosis Newborn Screening Programs: Cystic Fibrosis Foundation Workshop Report

Newborn screening for cystic fibrosis offers the opportunity for early intervention and improved outcomes. This summary, resulting from a workshop sponsored by the Cystic Fibrosis Foundation to facilitate implementation of widespread high quality cystic fibrosis newborn screening, outlines the steps necessary for success based on the experience of existing programs. Planning should begin with a workgroup composed of those who will be responsible for the success of the local program, typically including the state newborn screening program director and cystic fibrosis care center directors. The workgroup must develop a screening algorithm based on program resources and goals including mechanisms available for sample collection, regional demographics, the spectrum of cystic fibrosis disease to be detected, and acceptable failure rates of the screen. The workgroup must also ensure that all necessary guidelines and resources for screening, diagnosis, and care be in place prior to cystic fibrosis newborn screening implementation. These include educational materials for parents and primary care providers; systems for screening and for providing diagnostic testing and counseling for screen-positive infants and their families; and protocols for care of this unique population. This summary explores the benefits and risks of various screening algorithms, including complex situations that can occur involving unclear diagnostic results, and provides guidelines and sample materials for state newborn screening programs to develop and implement high quality screening for cystic fibrosis.

Newborn Screening for Severe Combined Immunodeficiency; The Wisconsin Experience (2008–2011)

Severe combined immunodeficiency is a life-threatening primary immune deficiency characterized by low numbers of naïve T cells. Early diagnosis and treatment of this disease decreases mortality. In 2008, Wisconsin began newborn screening of infants for severe combined immunodeficiency and other forms of T-cell lymphopenia by the T-cell receptor excision circle assay. In total, 207,696 infants were screened. Seventy-two infants had an abnormal assay. T-cell numbers were normal in 38 infants, abnormal in 33 infants, and not performed in one infant, giving a positive predictive value for T-cell lymphopenia of any cause of 45.83% and a specificity of 99.98%. Five infants with severe combined immunodeficiency/severe T-cell lymphopenia requiring hematopoietic stem cell transplantation or other therapy were detected. In summary, the T-cell receptor excision circle assay is a sensitive and specific test to identify infants with severe combined immunodeficiency and severe T-cell lymphopenia that leads to life-saving therapies such as hematopoietic stem cell transplantation prior to the acquisition of severe infections.

Clarification of Laboratory and Clinical Variables That Influence Cystic Fibrosis Newborn Screening With Initial Analysis of Immunoreactive Trypsinogen

OBJECTIVES. To ensure that each newborn receives an equitable test of the highest possible sensitivity, we recognized the necessity to reassess immunoreactive trypsinogen and DNA issues in cystic fibrosis newborn screening algorithms. Our objectives included clarification of various factors that influence immunoreactive trypsinogen concentrations and resolution of long-standing questions about variations in immunoreactive trypsinogen levels among newborns. METHODS. Immunoreactive trypsinogen data on 660443 newborns who were born between July 1, 1994, and June 30, 2004, were abstracted from the Wisconsin State Laboratory of Hygiene databases and deidentified for analysis. Using a compiled data set, we analyzed various demographic characteristics to determine their role, if any, in immunoreactive trypsinogen variation. Specifically, season of birth, reagent lot, and birth weight were examined. Sensitivities of the most common cystic fibrosis newborn screening protocols, namely immunoreactive trypsinogen/immunoreactive trypsinogen and immunoreactive trypsinogen/DNA, were also investigated. RESULTS. Mean and 95th percentile immunoreactive trypsinogen levels were shown to vary by both season and reagent lot number and affect sensitivity of the assay. Low birth weight infants had significantly higher immunoreactive trypsinogen values than normal birth weight infants. Sensitivities were also found to vary on the basis of the algorithm used, with the highest sensitivity of 96.2% calculated for an immunoreactive trypsinogen/DNA protocol with 23 cystic fibrosis transmembrane conductance regulator mutation analyses compared with 80.2% with the immunoreactive trypsinogen/immunoreactive trypsinogen method used in 9 states. CONCLUSIONS. Floating, rather than fixed, cutoff values for the initial immunoreactive trypsinogen portion of any cystic fibrosis newborn screening protocol are generally necessary on the basis of the seasonal and reagent lot variations observed. Because of its lower sensitivity, immunoreactive trypsinogen/immunoreactive trypsinogen does not optimize detection of patients with cystic fibrosis.

OPTIMAL DNA TIER FOR THE IRT/DNA ALGORITHM DETERMINED BY CFTR MUTATION RESULTS OVER 14 YEARS OF NEWBORN SCREENING

BACKGROUND There has been great variation and uncertainty about how many and what CFTR mutations to include in cystic fibrosis (CF) newborn screening algorithms, and very little research on this topic using large populations of newborns. METHODS We reviewed Wisconsin screening results for 1994-2008 to identify an ideal panel. RESULTS Upon analyzing approximately 1 million screening results, we found it optimal to use a 23 CFTR mutation panel as a second tier when an immunoreactive trypsinogen (IRT)/DNA algorithm was applied for CF screening. This panel in association with a 96th percentile IRT cutoff gave a sensitivity of 97.3%, but restricting the DNA tier to F508del was associated with 90% (P<.0001). CONCLUSIONS Although CFTR panel selection has been challenging, our data show that a 23 mutation method optimizes sensitivity and is advantageous. The IRT cutoff value, however, is actually more critical than DNA in determining CF newborn screening sensitivity.

Prevalence of the C677T substitution of the methylenetetrahydrofolate reductase ( MTHFR ) gene in Wisconsin

Purpose The objective of this study was to estimate the prevalence of the C677T substitution of the MTHFR gene in the State of Wisconsin.Methods The MTHFR genotypes of 1059 randomly selected newborns were analyzed using PCR amplification, Hin fI restriction enzyme digestion, and electrophoresis. The frequency of the substitution was calculated in different genders and statistically analyzed (Chi-square).Results Among 1059 newborn infants, about 59% had a C/C homozygous genotype, 33% had a C/T heterozygous genotype, and the remaining 8% had a T/T homozygous genotype. The frequencies for the C and T alleles were 76% (p) and 24% (q), respectively. There were no significant differences between males and females.Conclusion The study provides a fair estimate for the prevalence of the C677T substitution of the MTHFR gene in the general population in Wisconsin, which will facilitate further investigations of the pathogenic effects of the gene.

Tandem Mass Spectrometry in the Newborn Screening Laboratory

A common definition of newborn screening is “the presumptive identification of unrecognized congenital disorders by the application of laboratory tests to an entire population.” Newborn screening began in the 1950s, when Robert Guthrie developed a screening test for the metabolic disorder phenylketonuria (PKU) based on measuring the level of the amino acid phenylalanine in dried, whole blood specimens collected on filter paper. The immediate success prompted similar, mandated “PKU Screening” in all states by the mid-1960s. Subsequently, test methods were developed for other congenital or metabolic disorders including hypothyroidism, maple syrup urine disease, galactosemia, and biotinidase. The paradigm involved a separate test procedure for each disorder. In the 1990s, that paradigm radically changed with the introduction of tandem mass spectrometry (MS/MS) into the newborn screening laboratory. Tandem mass spectrometry is a technique which uses 1 blood spot specimen to detect a multiple of potential disorders. MS/MS in the Laboratory The MS/MS technologies for routine use in high production laboratories (ie, newborn screening laboratories) have evolved from liquid chromatography/mass spectrometer (LCMS) systems. The 1970s and 1980s saw several advances in mass spectrometry instrumentation that included improved sample introduction techniques such as fast atom bombardment (FAB) and fast ion bombardment (FIB). Also the development in the 1980s of quadrupole (4 magnetic rods) units, linking them in series, and controlling the function (separation, fragmentation, and detection) of each unit led to today’s tandem mass spectrometry systems. Concurrently, experimentation with sample preparation techniques improved sensitivity and reproducibility by incorporating procedures based on the formation of