Duchenne muscular dystrophy (DMD/Duchenne) is a progressive X-linked disease and is the most common pediatric-onset form of muscular dystrophy, affecting approximately 1:5000 live male births. DNA testing for mutations in the dystrophin gene confirms the diagnosis of this disorder. This study involves assessment of screening newborns for DMD using an immunoassay for muscle-type (MM) creatine kinase (CK) isoform—the GSP Neonatal CK-MM kit. Comparisons were made with CK activity determination by fluorescence measurement. In addition, the study evaluated the effect of gestational age, age of infant at time of sampling and how stable the CK-MM was over time. This assay discriminates well between normal, unaffected and Duchenne affected populations and is suitable for Duchenne newborn screening.

The synthesis of novel Tb"' labels suitable for protein labelling are reported. Their luminescence properties as antibody conjugates were measured and compared to the results of corresponding Tb"' chelates of the parent ligand structures. When the lowest triplet-state energy level of the parent donor ligand was over 23 000 cm-I, i. e., the energy gap between the 5D, level of Tb"' and the lowest triplet-state energy level of the ligand exceeded 2600cm-', the label derivative with a long decay time (~=1.35-2.93 ms) and a high luminescence yield (E . 0 = 3 770-4 560) was found to be suitable for bioaffinity assays.Introduction. -Long-lifetime emitting lanthanide chelates as sensitive labels or probes, and time-resolved fluorometry in detection have already been used in a number of applications in bioaffinity assays [l].In commercial systems, due to the many requirements of optimal lanthanide chelate labels, compromises have been made, e.g., the detection comprises two separate steps, as a direct measurement of the analyte without any enhancement step is impossible [2]. In this respect, these technologies are not suitable for all applications, such as in situ hybridization, immunohistochemistry, homogeneous assays, and fluorescence imaging. In addition to sensitive bioaffinity assays, new highly luminescent and stable lanthanide labels permit the development of multilabel, miniaturized assay devices with simplified protocols and thus make it possible to perform multiparametric assays on sub-microliter volumes of samples. A lot of research effort has been directed to the design and synthesis of optimal labels also suitable for the applications mentioned above. The chelating agents commonly used for the sensitization of Eu"' and Tb"' ion luminescence include P-diketones

CK-MM can be reliably quantified in blood spots. The development of this CK-MM assay on a commercial immunoassay analyzer would enable standardized and high-throughput newborn blood spot screening of DMD.

The availability of an intrinsically fluorescent, inert, and stable Eu chelate label made it feasible to design one-step all-in-one immunoassays with time-resolved fluorometry for detection. Both competitive and noncompetitive immunoassays are performed in microtitration wells containing all assay-specific components in a stable dry form. Only the sample and one assay buffer common for all analytes need to be added. Model assays for human chorionic gonadotropin (hCG), alpha-fetoprotein (AFP), and progesterone all reached equilibrium in 15 min or less without compromising the performance characteristics of the measurements, all of which perform at least equivalent to state-of-the-art assays. The detection limits for hCG, AFP, and progesterone were 0.3 IU/L, 0.1 microgram/L, and 0.5 nmol/L, respectively. The assay ranges for hCG and AFP were linear to 5000 IU/L and 1200 micrograms/L, respectively. The immunoassay format can be readily implemented in a fully automated random-access immunoassay system with optimal performance characteristics and no handling of analyte-specific assay components.