Birth Weight- or Gestational Age-adjusted Second-tier LCMSMS Cutoffs Improve Newborn Screening for CAH in New Zealand

Development and evaluation of a candidate reference measurement procedure for detecting 17α-hydroxyprogesterone in dried blood spots using isotope dilution liquid chromatography tandem mass spectrometry

17α-Hydroxyprogesterone (17α-OHP) quantification in dried blood spots (DBS) is essential for newborn screening for congenital adrenal hyperplasia (CAH), which is challenging due to its low physiological concentration. The high false-positive rates of immunoassays necessitate the development of more accurate methods. Liquid chromatography tandem mass spectrometry (LC-MS/MS) offers increased specificity and sensitivity, yet standardized procedures for 17α-OHP measurement are required for clinical application. A candidate reference measurement procedure (cRMP) using isotope dilution LC-MS/MS was developed for 17α-OHP quantification in DBS. By utilizing stable isotope-labeled D8-17α-OHP as an internal standard, the cRMP was optimized, covering sample preparation, calibration, and LC-MS/MS analysis. The method performance was validated across several parameters, including precision, accuracy, specificity, detection limits, and matrix effects. Clinical applicability was further assessed through the establishment of reference intervals for healthy newborns. The developed cRMP exhibited a linear range of 1.00 to 80.00 ng/mL for 17α-OHP, with detection and quantification limits of 0.14 ng/mL and 0.52 ng/mL, respectively. Inter- and intraday precision demonstrated coefficients of variation within 1.27 to 5.69%. The recovery rates and matrix effects were well within acceptable limits, ensuring method reliability. Clinical application showed distinct reference intervals for healthy newborns that were unaffected by sex but influenced by weight and gestational age. This method significantly enhances CAH diagnostic accuracy in newborns, providing a valuable tool for clinical laboratories and improving newborn screening program standardization and traceability.

Current Status of Newborn Bloodspot Screening Worldwide 2024: A Comprehensive Review of Recent Activities (2020-2023)

Newborn bloodspot screening (NBS) began in the early 1960s based on the work of Dr. Robert "Bob" Guthrie in Buffalo, NY, USA. His development of a screening test for phenylketonuria on blood absorbed onto a special filter paper and transported to a remote testing laboratory began it all. Expansion of NBS to large numbers of asymptomatic congenital conditions flourishes in many settings while it has not yet been realized in others. The need for NBS as an efficient and effective public health prevention strategy that contributes to lowered morbidity and mortality wherever it is sustained is well known in the medical field but not necessarily by political policy makers. Acknowledging the value of national NBS reports published in 2007, the authors collaborated to create a worldwide NBS update in 2015. In a continuing attempt to review the progress of NBS globally, and to move towards a more harmonized and equitable screening system, we have updated our 2015 report with information available at the beginning of 2024. Reports on sub-Saharan Africa and the Caribbean, missing in 2015, have been included. Tables popular in the previous report have been updated with an eye towards harmonized comparisons. To emphasize areas needing attention globally, we have used regional tables containing similar listings of conditions screened, numbers of screening laboratories, and time at which specimen collection is recommended. Discussions are limited to bloodspot screening.

International Newborn Screening Practices for the Early Detection of Congenital Adrenal Hyperplasia

INTRODUCTION

Newborn screening (NBS) programmes vary internationally in their approach to screening. Guidelines for congenital adrenal hyperplasia (CAH) screening recommend the use of two-tier testing and gestational age cutoffs to minimise false-positive results. The aims of this study were to describe (1) the approaches; (2) protocols used; and (3) available outcomes for CAH screening internationally.

METHODS

All members of the International Society for Neonatal Screening were asked to describe their CAH NBS protocols, with an emphasis on the use of second-tier testing, 17-hydroxyprogesterone (17OHP) cutoffs, and gestational age and birth weight adjustments. If available, screening outcomes were requested.

RESULTS

Representatives from 23 screening programmes provided data. Most (n = 14; 61%) recommend sampling at 48-72 h of life. Fourteen (61%) use single-tier testing and 9 have a two-tier testing protocol. Gestational age cutoffs are used in 10 programmes, birth weight cutoffs in 3, and a combination of both in 9. One programme does not use either method of adjusting 17OHP cutoffs. Case definition of a positive test and the response to a positive test differed between programmes.

CONCLUSIONS

We have demonstrated significant variation across all aspects of NBS for CAH, including timing, the use of single versus two-tier testing and cutoff interpretation. Collaboration between international screening programmes and implementation of new techniques to improve screen efficacy will facilitate ongoing expansion and quality improvement in CAH NBS.

Evaluation of a New Laboratory Protocol for Newborn Screening for Congenital Adrenal Hyperplasia in New Zealand

Between 2005 and 2021, 49 cases of classical congenital adrenal hyperplasia were diagnosed in New Zealand, 39 were detected in newborns and 10 were not detected by screening. Currently, for every case of CAH detected by screening, 10 false-positive tests are encountered. Second-tier liquid chromatography-tandem mass spectrometry (LCMSMS) has the potential to improve screening sensitivity and specificity. A new laboratory protocol for newborn screening for CAH was evaluated. Birthweight-adjusted thresholds for first- and second-tier 17-hydroxyprogesterone, second-tier 21-deoxycortisol and a steroid ratio were applied to 4 years of newborn screening data. The study was enriched with 35 newborn screening specimens from confirmed CAH cases. Newborn screening was conducted on 232,542 babies, and 11 cases of classical CAH were detected between 2018 and 2021. There were 98 false-positive tests (specificity 99.96%, PPV = 10.1%) using the existing protocol. Applying the new protocol, the same 11 cases were detected, and there were 13 false-positive tests (sensitivity > 99.99%, PPV = 45.8%, (X2 test p < 0.0001). Incorporating the retrospective specimens, screening sensitivity for classical CAH was 78% (existing protocol), compared to 87% for the new protocol (X2 test p = 0.1338). Implementation of LCMSMS as a second-tier test will improve newborn screening for classical CAH in New Zealand.