Differences in Newborn Screening Results Among Women with Gestational Diabetes Mellitus

Abstract Multiple studies undertaken on cord blood demonstrate analyte perturbations in infants exposed to gestational diabetes mellitus (GDM). Cord blood as a sample is influenced by maternal and placental metabolism. Newborn screening (NBS), performed after the first 24 hours of life reflects early neonatal metabolism. We compared NBS analytes between women with and without GDM with different management approaches in the Treatment of Booking of Gestational Diabetes (TOBOGM) pilot randomised controlled trial. Pregnant women with GDM risk factors were randomised to early or deferred GDM treatment following an oral glucose tolerance test (<20 weeks gestation). Women without GDM served as "decoys". From the decoy group 11 developed GDM (screened at 26-28 weeks), were analysed separately; their results were compared with the other groups. De-identified controls were chosen from NBS results from the same analytic run matched for sex, birthweight and gestational age. Results were available for 73/78 women participating in the pilot and 358 de-identified controls. Tyrosine levels (μmol/l; whole blood)were higher in the late GDM group vs early, deferred treatment, and decoy groups (medians:106.28; IQR: 96.73-151.11) (76.33; 64.64-97.90) (75.68; 66.59-110.88)(73.74; 58.32-90.36) (p=0.009) and remained elevated when compared to normal, age-matched controls (106.28; 96.73-151.11) (87.26; 68.55-111.26) (p value=0.01) Immunoreactive trypsinogen (μgm/l; whole blood)was highest in the early treatment group when compared with group-specific controls (22.30; 13.90-29.90 vs 14.00, 10.60-21.10) (p=0.02). These results provide evidence of biochemical perturbations detectable on NBS of in-utero exposure to hyperglycemia and treatment and provide data for hypothesis building.

Information overload--new technologies, can we store the data?

Computerization within newborn screening programs is a developing issue. To date two basic approaches to data storage have been used: (1) a storage system for babies diagnosed with a disorder, (2) a comprehensive system with long-term details for all patient samples, tests performed, test results and interpretations. It usually provides efficient real-time reports for various clinical and quality control requirements and easy access to an inborn errors registry. Within the last decade there have been two new technologies adapted to routine use in newborn screening laboratories: (1) tandem mass spectrometry for selected amino acids and acyl carnitine, and (2) DNA mutational analysis of PCR products. Both technologies present data storage challenges. Both are capable of providing large files of information for a sample. Consideration must be given to how these data are stored, whether all results including a graphical representation or DNA sequence data are kept or whether only final results for specific analytes are stored. Many new analytical technologies can only be incorporated into routine programs as a result of advances in hardware and software allowing better access to, and storage of, data.

Newborn screening--is it really that simple?

The incorporation of tandem mass spectrometry (MSMS) into an existing newborn screening program is an evolving process. Limited worldwide experience has ensured that all stages of reliability testing need to be followed. These include a literature review to establish methodology and analytes/disorders for testing and a pilot screening project including assaying archival samples from subjects with proven target disorders. Algorithms used for analyte concentrations and the relationships of various analytes to one another for resample criteria need to be continually reassessed to maximise screening specificity, sensitivity and positive predictive value. Since 1st of April 1998, the NSW Newborn Screening Program has screened 320, 848 babies using electrospray MSMS for selected amino acids and acyl camitines. Screening for amino acids has led to requests for 415 repeat samples with 94 babies referred for further testing. Of these 73 had a disorder of amino acid metabolism, including 43 with persistent hyperphenylalaninemia (36 of whom had PKU, 2 had a pterin pathway defect, 5 HPAA). Screening for acyl carnitines has led to requests for 245 repeat samples with 63 babies referred for further investigation. Of these 44 had a diagnosed disorder, including 15 with medium chain acyl CoA dehydrogenase deficiency. Five babies with confirmed disorders detectable with MS/MS had negative test results. The cost of screening using MSMS was only $A0.50 more than the method for screening for PKU and homocystinuria alone (ie the bacterial inhibition assays) and has allowed detection of an additional 74 babies at least 48 of whom have a diagnosis for which early treatment seems clearly beneficial. MSMS has shown a sensitivity of 95.9% and specificity of 99.8% in our laboratory with a positive predictive value of 18%.