Markedly elevated neonatal immunoreactive trypsinogen levels in the absence of cystic fibrosis gene mutations is not an indication for further testing. Issue 3 (21st October 2005)

• Record Type: Journal Article
• Authors: Massie, J; Curnow, L; Tzanakos, N; Francis, I; Robertson, C F
• Is Part Of: Archives of disease in childhood. Volume 91:Issue 3(2006)
• Page Start: 222
• Page End: 225
• Publication Date: 2005-10-21
• Subjects: CF, cystic fibrosis -- CFTR, cystic fibrosis transmembrane conductance regulator -- MI, meconium ileus -- MoM, multiples of median -- NBS, newborn screening -- PPV, positive predictive value; newborn screening -- cystic fibrosis -- immunoreactive trypsinogen; Children -- Diseases -- Periodicals; Infants -- Diseases -- Periodicals; 618.920005
• DOI: 10.1136/adc.2005.081349
• Languages: English
• ISSNs: 0003-9888

Abstract

Abstract : Aims: To investigate the immunoreactive trypsinogen (IRT) values above the usual 99th centile laboratory cut-off and determine the value of offering further testing to those infants with a markedly elevated IRT but no cystic fibrosis transmembrane regulator (CFTR) gene mutation identified by the screening programme. Methods: All babies born in Victoria, Australia, between 1991 and 2003, were screened by IRT followed by CF gene mutation analysis. Results: Of the 806 520 babies born, 9268 with the highest IRT levels had CFTR mutation analysis. There were 123 ΔF508 homozygotes and 703 heterozygotes (86 with CF, 617 carriers). A total of 8442 babies had no CFTR gene mutation, of whom 18 (0.21%) had CF. The total number of CF babies with IRT greater than the laboratory cut-off was 227 (2.4%). The IRT results of the CF patients were distributed normally, with the majority above the laboratory cut-off of newborn IRT results. There was no evidence of an excess of babies with CF in the very highest levels of IRT above the 99th centile. Conclusions: Only a small proportion of babies with a neonatal IRT >99th centile have CF. Additional CF testing for infants with an elevated IRT but no CFTR gene mutation has an extremely low yield, no matter how high the IRT result.