Increased prevalence of false positive hemoglobinopathy newborn screening in premature infants

The objective was to investigate the specificity of the hemoglobinopathy newborn screening in premature neonates as compared to term neonates.

The screening results from infants suspected to have hemoglobinopathy disease identified by the Florida Newborn Screening Program for years 2002-2007 were compared to the corresponding confirmatory testing. The risks for false positives for preterm and full term newborns were calculated by Chi-square or the Cochran-Armitage test for trend. Isoelectric focusing and HPLC were the methods of hemoglobin screening.

Over 2,300 neonates (1/576 neonates born in Florida) were suspected to have hemoglobinopathy. The most common abnormal pattern in term and preterm infants (gestational age 22-36 weeks) suggesting disease at screening was FS. Overall, 93% of the children who screened positive for FCA and 64% of infants identified with FSA were later confirmed with trait. FSC was confirmed in 96% of the cases in both preterm and term infants. Compared to term newborns, preterm newborns were more likely to have a false positive result for FS or FC at screening. Twenty-three percent of preterms with FS and 59% of preterms with FC were diagnosed as traits by confirmatory testing, compared to only 2% and 6% for term infants (P < 0.001).

As compared to term newborns, more preterm newborns with trait were misidentified as having sickle cell anemia or hemoglobin C at screening. We speculate that abnormal hemoglobins may precede the development of hemoglobin A during fetal life.