By Crina Frincu-Mallos, PhD
WASHINGTON, DC -- October 19, 2009 -- High immunoreactive trypsinogen (IRT) levels are reliable predictors of mortality in infants with very low birth weight, according to a study presented here at the 2009 American Academy of Pediatrics (AAP) National Conference & Exhibition.
"IRT levels may be elevated in preterm infants resulting in false-positive results for cystic fibrosis newborn screening," said Sarvin Ghavam, MD, Pediatrics, duPont Hospital for Children, Wilmington, Delaware, on October 16. "This has been attributed to acute illness in this vulnerable population but has not been further characterised."
"As newborn screening for cystic fibrosis expands, neonatologists need to be aware of the potential for increased IRT in those infants who die, thereby limiting the usefulness and specificity of IRT as a screen for cystic fibrosis in this population of babies," said Dr. Ghavam.
Dr. Ghavam and colleagues aimed to find out whether IRT levels in infants with very low weight at birth correlate with gestational age and/or illness severity. They also evaluated the possible relationship between elevated IRT levels and mortality.
The study included 175 infants with weight at birth <1,500 g, who were admitted in the Neonatal Intensive Care Unit at Christiana Hospital between July 2006 and July 2008.
Eligible infants had IRT measured on their fifth day of life, according to the State of Delaware Newborn Screening Program, explained the investigators.
The statistical analysis of the data was performed using analysis of variance (ANOVA), Mann-Whitney U test, and multivariable logistic regression. Necrotising enterocolitis (NEC) was defined as minimum of Bell's Stage 2.
According to Dr. Ghavam, none of the study infants were diagnosed with cystic fibrosis.
The mean IRT was 33.6 +- 18.8 mcg/L and median 29.8 mcg/L.
The IRT levels were significantly higher in the infants who died (n = 15), compared with those who survived: 43.7 +- 20.9 mcg/L versus 32.6 +- 18.4 mcg/L (P = .03). Infants with an IRT >30 mcg/L had increased odds of death, even after controlling for confounding variables including birth weight (odds ratio [OR] = 5.6; 95% confidence interval [CI], 1.3-23).
Furthermore, the investigators found that high levels of IRT did not correlate with either gestational age (R = -0.08; P = .32) or illness severity (R = 0.03; P = .75). However, the data analysis indicates a slight inverse correlation of high IRT levels with birth weight, noted Dr. Ghavam (R = -0.19; P = .02).
No statistically significant difference was found between infants developing NEC (n = 11) and those who did not, in terms of IRT levels, the values being 33.6 +- 14.3 mcg/L and 33.6 +- 19.1 mcg/L, respectively (P = .99).
"These data expand existing data regarding elevated IRT in ill premature infants, particularly in light of its association with mortality," said Dr. Ghavam, adding that the finding that elevated IRT in infants without cystic fibrosis is associated with mortality requires further evaluation.
[Presentation title: Immunoreactive Trypsinogen (IRT) Is Elevated in Very Low Birth Weight Infants Who Die. Abstract 6358]
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