Prenatal Diagnosis of Hemoglobinopathies

Perimortem laboratory investigation of genetic metabolic disorders

Over 400 rare, biochemically diverse genetic metabolic disorders (inborn errors of metabolism) have been described and the list is growing by the month. Although recent advances in the diagnosis and treatment of these disorders have substantially improved the prognosis for many of them, including those presenting in the neonatal period, a proportion of affected individuals die before the diagnosis can be confirmed and, in some cases, before the diagnosis is even considered. This review will provide an outline of the range of clinical presentations seen in neonates with genetic metabolic disorders and provide a practical approach for rapid biochemical screening for these disorders. In addition, suggested guidelines are given for the collection of relevant samples in the perimortem period, the aim being to maximize the chance of identifying any underlying genetic metabolic disorder.

Preventing morbidity and mortality from sickle cell disease. A public health perspective

CONTEXT

Sickle cell disease is a group of conditions characterized by production of abnormal hemoglobin, with clinical manifestations that vary by genotype and age.

OBJECTIVE

To discuss current public health issues associated with sickle cell disease, and approaches to preventing complications from these conditions in the United States.

DESIGN

Literature review.

RESULTS

Most clinical interventions for people with sickle cell disease discussed in the medical literature can be classified as tertiary prevention: for example, therapy to ameliorate anemia, reduce the frequency of pain crises, or prevent stroke recurrences. A form of secondary prevention, newborn screening, has emerged as an important public health approach to identifying affected children before they develop complications. Newborn screening is the starting point for simple public health strategies such as parental education, immunization, and penicillin prophylaxis. Identification of affected families by newborn or community screening programs has also been an entry point for genetic counseling, although utilization of prenatal testing has varied by factors such as geographic location. Public health agencies have had significant involvement with funding, policy making, and formulation of laboratory and clinical guidelines for sickle cell disease. Since the introduction of penicillin prophylaxis policies, newborn screening, new immunizations, and comprehensive medical care centers, the survival of young children with sickle cell disease has improved.

CONCLUSIONS

Although the efforts of preventive medicine providers in public health programs are not solely responsible for the improved survival of children with sickle cell disease, such programs remain an important component in preventing sickle cell complications.

Nursing management of children with sickle cell disease: an update

This article reviews current trends in managing children with sickle cell disease (SCD). The pathophysiology, medical and nursing management, and complications of SCD are discussed. Current trends and research findings related to improving the prognosis of children with SCD are offered. The importance of the nurse's role in educating the family about the disease process and clinical interventions to prevent or manage complications are stressed. Lastly, a nursing care plan is offered which focuses on pertinent nursing diagnosis.

Trapped-oligonucleotide nucleotide incorporation (TONI) assay, a simple method for screening point mutations

We present a simple screening method for detecting a known point mutation, using only one 5'-biotinylated oligonucleotide primer, with its 3' end adjacent to the mutation site. In parallel reactions, an amplified DNA template encompassing the biotinylated oligonucleotide and mutation site undergoes 40 step-cycles of single nucleotide incorporation using Taq thermostable DNA polymerase and only one radioactive [alpha-32P]dNTP, specified by either the normal or mutant sequence. The oligonucleotides, now radioactively labelled at the 3' end according to the template sequence, are then trapped by streptavidin-coated magnetic beads, and the percent of radiolabel incorporated is determined directly by the Cerenkov method in a scintillation counter. The trapped-oligonucleotide nucleotide incorporation (TONI) assay has been used for the screening of a mitochondrial polymorphism, and has also been shown to distinguish the genotypes of hemoglobin A/C, A/A, A/S, and S/S. It is reproducible over at least a 100-fold range of radioisotope and a 10-fold range of oligonucleotide primer. This method is particularly useful for diagnosing mutations which do not produce alterations detectable by restriction enzyme analysis, since optimization of conditions is rarely necessary. In addition, it requires only a single oligonucleotide, and no electrophoretic separation of the allele-specific products. It thus represents an improved and simplified modification of the existing allele-specific primer extension methods (Kuppuswamy et al., Proc Natl Acad Sci USA 88:1143-1147, 1991; Sokolov, Nucl Acids Res 18:3671, 1989; Syvanen et al., Genomics 8:684-692, 1990).