Efficacy of Liquid-chromatography and Radioimmunoassay in False-positives’ Drop-off in CAH Newborn Screening
Authors' conclusion
Measurement of 17OHP by LC-MS/MS provides the best performance for serum confirmatory tests and may be complemented by the (17OHP+Δ4)/cortisol ratio analysis. Genotyping is useful mainly to resolve persistently indeterminate biochemical results.
Study context
- Population
- Newborns in CAH newborn screening recalled for N17OHP ≥ 2 × 99.5th for serum confirmatory testsnewborns evaluated
- Participants
- 708,437 newborns
- Exposure
- Serum 17OHP by radioimmunoassay (RIA) vs LC-MS/MS as confirmatory tests after positive CAH newborn screening (NBS)
- Outcome
- PPV of serum confirmatory tests
Methodological detailsdiagnostic accuracy (ROC curves), Altered hormonal results submitted to CYP21A2 genotyping
- Diagnostic accuracy (ROC curves)
- Altered hormonal results submitted to CYP21A2 genotyping
Main finding
As reported in the abstract
Serum 17OHP remained increased; PPV
| Group | Value | PPV |
|---|---|---|
| RIA | 26% | 30% |
| LC-MS/MS | 11% | 49% |
Value
RIA26%
LC-MS/MS11%
PPV
RIA30%
LC-MS/MS49%
Observational data: associations, not effects.
Further findings
Recall rate of N17OHP (first tier)
- Recall rate
- 0.03%
Diagnoses
- Newborns (NBs) diagnosed with classical forms
- 58
- Asymptomatic NBs with persistently increased serum 17OHP
- 32
ROC: false vs true positives
- 17OHP/LC-MS/MS highest diagnostic performance; cutoff 48.3 ng/mL (146.3 nmol/L) = 100% sensitivity
- (17OHP+Δ4)/cortisol ratio highest discriminative ability; cutoff 24.9 = 100% PPV
- Serum 21DF good performance, comparable to 17OHP by LC-MS/MS (99% specificity)
Original publication
Efficacy of Liquid-chromatography and Radioimmunoassay in False-positives’ Drop-off in CAH Newborn Screening. J Clin Endocrinol Metab. Published 11 March 2026. doi:10.
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