Direct and rapid mass spectral fingerprinting of maternal urine for the detection of Down syndrome pregnancy

Abstract

BackgroundThe established methods of antenatal screening for Down syndrome are based on immunoassay for a panel of maternal serum biomarkers together with ultrasound measures. Recently, genetic analysis of maternal plasma cell free (cf) DNA has begun to be used but has a number of limitations including excessive turn-around time and cost. We aimed to develop an alternative method based on urinalysis that is simple, affordable and accurate.Method101 maternal urine samples sampled at 12–17 weeks gestation were taken from an archival collection of 2567 spot urines collected from women attending a prenatal screening clinic. 18 pregnancies in this set subsequently proved to be Down pregnancies. Samples were either neat urine or diluted between 10 to 1000 fold in dH2O and subjected to matrix assisted laser desorption ionization (MALDI), time of flight (ToF) mass spectrometry (MS). Data profiles were examined in the region 6,000 to 14,000 m/z. Spectral data was normalised and quantitative characteristics of the profile were compared between Down and controls.ResultsIn Down cases there were additional spectral profile peaks at 11,000-12,000 m/z and a corresponding reduction in intensity at 6,000-8,000 m/z. The ratio of the normalised values at these two ranges completely separated the 8 Down syndrome from the 39 controls at 12–14 weeks. Discrimination was poorer at 15–17 weeks where 3 of the 10 Down syndrome cases had values within the normal range.ConclusionsDirect MALDI ToF mass spectral profiling of maternal urinary has the potential for an affordable, simple, accurate and rapid alternative to current Down syndrome screening protocols.

The importance of gestational age in first trimester, maternal urine MALDI-Tof MS screening tests for Down Syndrome

“…Thus, one m/z bin or mass spectra peak, may be signi icant as a marker of Downs at an early gestational age but not a later gestation and vice-versa. Changes in pro iles and quantitative values with gestational age was noted in our original study [13], but this was not as dramatic as seen here for the lower spectral masses now included in our analysis.…”

“…Women were excluded from the study when they were found to have urinary tract infection or contamination in their midstream urine samples. The maternal urine (20-30 ml) were collected between 2007 and 2008 and frozen at -80 o C. Twenty urine samples from these women were subsequently found to be carrying a Trisomy 21 (Downs Syndrome) fetus and a further 100 urine samples identi ied not to be carrying an aneuploid fetus [13].…”

“…In particular, we have proposed that the adoption of this technology in examination of maternal pregnancy urine samples for the detection of Downs syndrome. This will have equally dramatic bene its to prenatal screening costs and speed of clinical management [13].…”

“…The premise of our MALDI-ToF MS approach is not the measurement of a known single, or multiple biomarkers, but spectral pro iling and pattern recognition as the basis of predicting a pregnancy outcome. In order to achieve comparative analysis, we have already shown that spectral normalization of de ined mass bins as area under the curve is a promising approach [13]. In our previous study, we only examined the spectral pattern from 6000 to 14000 m/z, as that incorporated the spectral pattern of the major urinary metabolite of human chorionic gonadotropin (hCG) -beta core fragment hCG (hCGβcf).…”

Hexagonal Mesoporous Silica as a Rapid, Efficient and Versatile Tool for MALDI-TOF MS Sample Preparation in Clinical Peptidomics Analysis: A Pilot Study

“…Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) has recently captured significant attention in clinical chemistry for the ability of screening with high-throughput small amounts of clinical samples and for rapidly detecting biomolecules serving as disease biomarkers [4,5,6]. Comparative MALDI-TOF MS analysis may help in monitoring changes of expression patterns of disease specific peptides (between healthy and diseased individuals), with the potential to deliver fast and sensitive clinical assays.…”