Evaluation of Robust Estimators Applied to Fluorescence Assays

  • PDF / 969,971 Bytes
  • 10 Pages / 600.05 x 792 pts Page_size
  • 87 Downloads / 221 Views

DOWNLOAD

REPORT


Research Article Evaluation of Robust Estimators Applied to Fluorescence Assays ¨ a, ¨ 1 S. Peltonen,1 J. Soukka,2 E. Alban, ´ 1 J. T. Soini,2, 3, 4 and U. Ruotsalainen1 M. Vastil 1 Institute

of Signal Processing, Tampere University of Technology, P.O.Box 553, 33101 Tampere, Finland Diagnostics, 20521 Turku, Finland 3 Laboratory of Biophysics, University of Turku, 20521 Turku, Finland 4 Centre for Biotechnology, University of Turku and Abo ˚ Akademi University, 20520 Turku, Finland 2 Arctic

Correspondence should be addressed to M. V¨astil¨a, [email protected] Received 24 January 2007; Revised 6 June 2007; Accepted 14 October 2007 Recommended by Liang-Gee Chen We evaluated standard robust methods in the estimation of fluorescence signal in novel assays used for determining the biomolecule concentrations. The objective was to obtain an accurate and reliable estimate using as few observations as possible by decreasing the influence of outliers. We assumed the true signals to have Gaussian distribution, while no assumptions about the outliers were made. The experimental results showed that arithmetic mean performs poorly even with the modest deviations. Further, the robust methods, especially the M-estimators, performed extremely well. The results proved that the use of robust methods is advantageous in the estimation problems where noise and deviations are significant, such as in biological and medical applications. Copyright © 2008 M. V¨astil¨a et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

1.

INTRODUCTION

Bioaffinity assays are used for determining the concentrations of biomolecules—analytes or antigens—of interest in several fields, such as clinical diagnostics and drug discovery. The method is based on using biological molecules of specific affinity towards the analyte for binding the analyte molecules on a surface and for labelling the analytes. In the fluorescence assays, the fluorophore label yields a measurable signal in the range of visible light proportional to the analyte concentration. In this work, the measurements have been carried out by applying the single-step ArcDia TPX assay technology [1, 2]. Figure 1 illustrates the solid phase assay, where microparticles are used as a binding surface to condense the analyte molecules. The ArcDia TPX technology has been used for the measurement of different assay types: microparticle-based assays with molecular labels (molecular measurement), assays of microparticle and nanoparticle complexes where nanoparticles are used as a labelling reagent (nanoparticle measurement), and liquid assays where the fluorochrome concentration in liquid is defined (liquid measurement) [2]. Recently, this technology has also been used for monitoring bacterial

growth. In that application, the bacterial cells are captured by microparticles and labeled with a specific fluorescent-labeled antibody. In the TPX te