Context Newborn screening for cystic fibrosis (CF) is included in many routine programmes but current strategies have considerable drawbacks, such as falsepositive tests, equivocal diagnosis and detection of carriers.Objective To assess the test performance of two newborn screening strategies for CF. Design, setting and participants In 2008 and 2009, CF screening was added to the routine screening programme as a prospective study in part of the Netherlands.Interventions Two strategies were performed in all newborns. In the first strategy, concentrations of immunoreactive trypsinogen (IRT) and pancreatitisassociated protein (PAP) were measured. In the second method, samples with IRT $60 mg/litre were analysed for 36 CFTR mutations, followed by sequencing when a single mutation was detected. Tests were positive only with two identified CFTR mutations. Main outcome Sensitivity, specificity and positive predictive value (PPV) of both screening strategies. Results 145 499 infants were screened. The IRT/PAP approach showed a sensitivity of 95.0%, a specificity of 99.897% and a PPV of 12.3%. Test properties for the IRT/ DNA/sequencing strategy were respectively 100%, 100% and 64.9%. Combining both strategies (IRT/PAP/ DNA/sequencing) led to a sensitivity of 95.0%, a specificity of 100% and a PPV of 87.5%.

NBSCF is as an economically justifiable public health initiative. Of the four strategies tested IRT-PAP is the most economic and this finding should be included in any decision making model, when considering implementation of newborn screening for CF.

BackgroundFalse-positive screening results in newborn screening for cystic fibrosis may lead to parental stress, family relationship problems and a changed perception of the child's health.Aim of the studyTo evaluate whether parental anxiety induced by a false positive screening result disappears after six months and to assess whether a special program to inform parents prior and during the screening procedure prevents or diminishes parental anxiety.MethodsProspective controlled study assessing the long term effects of false-positive test results of newborn screening for cystic fibrosis (NBSCF) on parental anxiety and stress by means of questionnaires sent to parents of 106 infants with a false positive newborn screening test and 318 randomly selected infants with a true negative screening test. Additionally we interviewed 25 parents of the false-positive group.ResultsParents showed negative feelings after being informed about the positive screening test result. After confirmation that their child was healthy and not suffering from CF, most parents felt reassured. After six months no difference in anxiety levels between both groups of parents was found. Well-informed parents in the false positive group experienced less stress.ConclusionsA positive screening test result induces parental anxiety but false positive test results in NBSCF do not seem to cause long-term anxiety. Well-informed parents show lower stress and anxiety levels.

Sex, birth weight, and gestational age lead to small differences in PAP concentrations without consequences for the screening algorithm. However, blood transfusion as well as performance of the heel prick after 168 hours (7 days) lead to clinically significant higher PAP levels and to a higher risk on a false-positive screening test result.

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