We thank Dr Wolter for his comment because he is absolutely right. Based on both the numbers of adrenogenital syndrome (AGS) in Table 1 and the laboratory results on the average specificity for 17-OH progesterone screening in 2005–2008 (page 16), the result is indeed a much higher number of false positive specimens and therefore a lower predictive value of the screening for AGS (12 771 × (100-specificity) =12 771 × 0.61=78).
In none of the testing procedures used for neonatal screening did the data on specificity among the screening laboratories vary as widely as for 17-OH progesterone screening. This may in part be due to the fact that at present there are no consistent cut-off values used. The main reason for the wide range, however, is the varying proportion of samples of preterm babies that individual laboratories receive from perinatal centers. In premature babies, 17-OH progesterone is often raised without AGS (one possible cause for error, Box2/B, page 18).
The positive predictive value for AGS screening of 3%, which was reported on page 16, relates to mature babies born at term (after 37 complete weeks of gestation). We should have made that clearer in the text.
Footnotes
Conflict of interest statement
The authors of both contributions state that no conflict of interest exists.
References
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