It is the most sensitive diagnostic test available and is used first line in all cases, but can miss balanced translocations and low-level mosaicism. Specific gene testing is available for certain disorders such as Rett syndrome, although these are expensive tests which arent widely available
Selective metabolic investigations may be useful in the absence of other identifiable causes, and the specific tests done will depend on the presentation. Inborn errors of metabolism causing metabolic disorders are rare and there are limited treatment options even if they are successfully diagnosed. Targeted MRI brain can be considered second line in selected patients, and is more likely to contribute to a diagnosis if the child has abnormal physical signs such as microcephaly, macrocephaly, a change in head circumference, focal neurological signs, or epilepsy.Neonatal screening is used in the UK (Guthrie test) and can diagnose certain inborn errors of metabolism before they cause significant developmental problems, with the aim to manage them so that no permanent damage occurs. Medium-chain acyl-CoA dehydrogenase deficiency
Homocysteinuria
Congenital hypothyroidism
Isovaleric acidaemia
Glutaricaciduria type 1
Maple syrup urine diseaseCanada, the US, and the Netherlands offer more extensive newborn screening, encompassing some other amino acid, organic, and urea cycle disorders

Management
The specific management of children with global developmental delay will depend on their individual needs and underlying diagnosis. Early intervention is essential to support the child to reach their full potential.
Formulation
Dakins original solution contained sodium hypochlorite (0.4% to 0.5%), prepared by treating calcium hypochlorite with sodium carbonate ("washing soda"). The solution left after removal of the insoluble calcium carbonate still contained some soda. Boric acid (4%) was then added as a buffering agent to maintain a pH of between 9 and 10. Dakin found that alkalinity outside this range was too irritating. The solution, while unstable, remains effective for at least a week, if made to the correct pH.Other formulations have been developed over time. In 1916, Marcel Daufresne substituted sodium bicarbonate for Dakins boric acid as buffering agent. This formulation is the basis of current commercial products.The concentration chosen by Dakin (0.5%) was the maximum highest concentration found tolerable to the skin. It is the concentration recommended by the U.S. Center for Disease Control (CDC) as a household disinfectant. In one study, bactericidal effects of sodium hypochlorite solution were observed at concentrations as low as 0.025%, without any tissue toxicity in vivo or in vitro. It recommended that concentration be adopted as a "modified Dakins solution" for wound dressing. See also
Chlorine-releasing compound
Hydrogen peroxide
Povidone-iodine
Phenol ("carbolic acid")
Eusol


== References ==