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The use of multiple maternal serum biochemical markers in screening for Down syndrome is gaining worldwide acceptance. We sought to study the impact of the potential instability of intact human chorionic gonadotropin (hCG) on free beta-hCG subunit, a marker that has recently been used successfully in such screening. We found that, in practice, any changes in free beta-hCG due to the instability of intact hCG do not inhibit the effectiveness of free beta-hCG as a marker for Down syndrome. This was proven by controlled laboratory experiments at various stress temperatures, freeze-thaw studies, and analysis of a large set of screening data with particular reference to time in transit for individual samples. Data from controlled dissociation studies demonstrate that any apparent increase in free beta-hCG due to the instability of intact hCG cannot be attributed simply to the dissociation of intact hCG. Finally, for large-scale mass population screening in areas of the world where transport delays, safety concerns, and high temperatures preclude the shipment of liquid whole blood, dried whole-blood spots in filter paper provide a suitable delivery system with many advantages.

Adrenoleukodystrophy (ALD) is an X-linked recessive disorder characterized by progressive demyelination of cerebral white matter and adrenal insufficiency. ALD is the most common peroxisomal disease, afflicting 1 in 20 000 male newborns. Patients with childhood ALD manifest changes of character or behavior and a decline of intelligence and visual or motor dysfunction as the first symptoms during school age. Most of them lapse into a vegetative state and die within several years of onset (1). Patients with all clinical subtypes, including childhood ALD, adolescent ALD, adult ALD (cerebral type), adrenomyeloneuropathy, and Addison disease without neurological symptoms, have defects in the ALD gene (2). Defective activity of peroxisomal lignoceroyl-CoA ligase is considered to lead to the accumulation of very long chain fatty acid (VLCFA) in various tissues and fluids as a secondary phenomenon (3)(4). Dietary erucic acid (C22:1) therapy may help prevent neurological deterioration in presymptomatic boys (5)(6). Patients in the early or presymptomatic stages may be candidates for bone marrow transplantation (5)(7). Gene therapy may also become possible. Screening for ALD, especially in the presymptomatic stage, will be important when these therapeutic methods are established, as in the cases of phenylketonuria or maple syrup urine disease. ALD is usually diagnosed by plasma VLCFA analysis (1)(8), sometimes followed by measurement of β-oxidation activity in cultured skin fibroblasts (9) and mutation analysis of the ALD gene (2)(10)(11)(12)(13)(14)(15)(16). However, screening requires a simpler and more economical method to deal with a large number of subjects. Utilization of a dried blood spot on filter paper …

We describe a sensitive, simple, and rapid two-site immunoenzymometric assay for thyrotropin in dried blood samples on filter paper, for use in screening for neonatal primary hypothyroidism. In this method, two dried-blood spots of 3 mm diameter (equivalent to about 5.4 microliter of blood) are incubated overnight with anti-thyrotropin-beta-D-galactosidase complex in an anti-thyrotropin coated tube. Then the enzyme activity in the washed tube is determined fluorophotometrically. The range of thyrotropin measurable is 10 to 160 milli-int. units/L blood. Values for thyrotropin in dried blood samples determined by this method and those determined by radioimmunoassay correlated highly (r = 0.96).