Results of three different screening strategies with an immunoreactive trypsinogen cut-off level of 60 μg/l (n=145 499)
| IRT/PAP | IRT/DNA/seq | IRT/PAP/DNA/seq | |
| Test positive, n (%) | 171 (0.12) | 37 (0.025) | 24 (0.016) |
| CF with MI* | 2 | 4 | 2 |
| CF, no MI | 19 | 20 | 19 |
| False positive | 146 | 0 | 0 |
| Equivocal diagnosis† | 4 | 13 | 3 |
| Test negative | 145 328 | 145 462 | 145 475 |
| No CF | 145 325 | 145 462 | 145 472 |
| CF with MI* | 2 | 0 | 2 |
| CF, no MI | 1 | 0 | 1 |
| Carriers | 0 | 67 | 8 |
| Sensitivity, % (95% CI) | 95.0 (73.1 to 99.7) | 100 (80.0 to 100) | 95.0 (73.1 to 99.7) |
| Specificity, % (95% CI) | 99.897 (99.879 to 99.912) | 99.991 (99.984 to 99.995) | 99.998 (99.993 to 100) |
| PPV, % (95% CI) | 12.3 (7.9 to 8.4) | 64.9 (47.4 to 79.3) | 87.5 (66.5 to 96.7) |
↵* Excluded from the analysis.
↵† Infants with an equivocal sweat test result and/or a second mutation associated with an unclear phenotype and a normal or equivocal sweat test (=false-positive screening test result).
CF, cystic fibrosis; IRT, immunoreactive trypsinogen; MI, meconium ileus; PAP, pancreatitis-associated protein; PPV, positive predictive value; seq, sequencing CFTR gene.