Improved precision of newborn screening for congenital adrenal hyperplasia using weight-adjusted criteria for 17-hydroxyprogesterone levels.
OBJECTIVE
To evaluate the efficacy and efficiency of weight-adjusted threshold levels for 17-hydroxyprogesterone (17-OHP) in screening newborn infants for 21 hydroxylase deficiency-congenital adrenal hyperplasia (21-OH-D-CAH).


METHODS
Analysis of the number of false-positive reports and diagnoses in infants, of 21-OH-D-CAH with the use of two strategies. Before October 1993, separate criteria for definite abnormal 17-OHP levels were established and implemented for 41,846 infants on the basis of birth weight: either less than 2200 gm (17-OHP level, 90 ng/ml) or 2200 gm or more (40 ng/ml). To reduce the burden of follow-up testing in low birth weight infants, criteria for definite abnormal 17-OHP results were statistically determined for four, rather than two, birth weight divisions: 1299 gm or less (17-OHP level > or = 165 ng/ml), 1300 to 1600 gm (> or = 135 ng/ml), 1700 to 2200 gm (> or = 90 ng/ml), and more than 2200 gm (> or = 40 ng/ml). These criteria were applied to the next 149,684 infants screened, and rates of false-positive test results and of false-positive diagnoses of 21-OH-D-CAH were compared.


RESULTS
Before implementation of four-tiered weight-adjusted 17-OHP criteria, 205 definite abnormal reports yielded four confirmed cases of 21-OH-D-CAH (positive predictive value = 2%; incidence of 21-OH-D-CAH = 1 in 10,461). With the revised criteria, 61 of 149,684 infants had definite abnormal results and 14 cases of 21-OH-D-CAH were confirmed (positive predictive value, 20%; incidence of 21-OH-D-CAH, 1 in 10,692). No undetected severe cases of 21-OH-D-CAH have been subsequently reported.


CONCLUSIONS
Weight-adjusted criteria for 17-OHP levels in screening for 21 -OH-D-CAH markedly reduced the number of false-positive results requiring immediate follow-up testing, particularly among low birth weight infants. Increased specificity afforded by these criteria was not accompanied by diminished sensitivity in detecting severe cases. Long-term follow-up of this screened cohort will determine whether the goals of newborn screening for 21-OH-D-CAH are adequately and efficiently fulfilled by this approach.
Allen
D B
DB
Department of Pediatrics, University of Wisconsin School of Medicine, Wisconsin State Laboratory of Hygiene, Marshfield Medical Center, and Children's Hospital of Wisconsin, Milwaukee, USA.
Hoffman
G L
GL
Fitzpatrick
P
P
Laessig
R
R
Maby
S
S
Slyper
A
A
D019326:17-alpha-Hydroxyprogesterone / Q000097:blood*; D000312:Adrenal Hyperplasia, Congenital / Q000097:blood / Q000175:diagnosis*; D001835:Body Weight; D005189:False Positive Reactions; D006801:Humans; D007230:Infant, Low Birth Weight / Q000097:blood; D007231:Infant, Newborn / Q000097:blood*; D015997:Neonatal Screening / Q000379:methods*
D019326:17-alpha-Hydroxyprogesterone