10 February 2012

Don't screen for adrenal hyperplasia in preemies

Researchers say that in preterm newborns, routine screening for adrenal hyperplasia due to 21-hydroxylase deficiency (21-OHD) is not worthwhile.


French researchers say that in preterm newborns, routine screening for adrenal hyperplasia due to 21-hydroxylase deficiency (21-OHD) is not worthwhile because the positive predictive value is very low in these babies.

Also, they say, preemies in neonatal ICUs are generally observed so closely that any adrenal crisis is likely to be noticed. But they stop short of recommending that screening of full-term newborns be discontinued, in a report this month in Archives of Pediatrics & Adolescent Medicine.

According to the National Institutes of Health, people with congenital adrenal hyperplasia lack an enzyme needed by the adrenal gland to make the hormones cortisol and aldosterone. Without these hormones, the body produces more androgen, a type of male sex hormone, and causes male characteristics to appear early (or inappropriately). It can affect both boys and girls.

Dr Jean-Claude Carel, at the Robert Debre Hospital in Paris, and colleagues explain that neonatal screening for 21-OHD by measuring 17-hydroxyprogesterone levels is common in Europe, the US and other Western countries.

The testing is controversial, however, because 17-hydroxyprogesterone levels vary with gestational age. In addition, accuracy can be compromised by cross-reaction with other corticosteroids, and female cases are readily apparent due to markedly virilised genitalia.

Universal 21-OHD screening was introduced in France in 1996, and the main objective of the current study was to evaluate its efficiency by retrospectively analysing data on all children born there from 1996 through 2003.

Altogether, 6 012 798 neonates were screened and 15 407 of the tests were positive. Most of the positive cases (91%) were born before term, the report indicates. Only 370 were considered to have congenital adrenal hyperplasia, of which 358 had the classic form of the condition, the authors report.

Screening results  

Screening helped diagnose 162 cases, but the test results were redundant in 74 children with a family history, 96 girls with genital abnormalities, and 13 boys diagnosed clinically before screening results were available.

The team identified 25 false-negative cases and calculated that sensitivity of screening was 93.5%. While the positive predictive value was moderate at 2.3% overall, it was only 0.4% in preterm neonates because of the high false-positive rate.

Based on the findings, Dr Carel and colleagues recommend that screening of preterm infants be discontinued, since "most preterm neonates are subject to careful paediatric care that should ensure that incipient SW (salt wasting) adrenal crises are readily recognised."

They also suggest that while screening of term infants should continue where the program is already in place, "careful consideration be given to its implementation in areas where this is not the case."

(Reuters Health and Health24, February 2012) 

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