In-depth Retrospective Review of Originally Negative Screening Mammograms from Women with Confirmed Breast Cancer

Objectives: We aim to contribute to the assessment of the screening performance in Flanders (Belgium) and to identify valuable mammograms for subsequent studies and training. Materials and Methods: Initially negative prior screening mammograms (sMx) of 210 women with confirmed breast cancer detected by the Flemish screening programme between 2011–2013 were reviewed by a highly experienced radiologist. The review of the prior sMx was performed in three steps: 1) only prior mammograms available; 2) with index sMx (=subsequent positive sMx) present; 3) with index sMx and clinical information present. Results: The radiological review yielded 94 (45%) mammograms ‘without suspicious lesions’, 77 (37%) ‘with minimal signs in at least one breast’, and 39 (19%) ‘with clearly visible tumours’. In univariate analyses, the reclassification of prior sMx was significantly associated with the date of the prior sMx, the need for a third reader for arbitration, image quality and the detector system used (computed radiography versus direct readout digital radiography), and it was not associated with the interval between screening rounds, age at prior sMx, breast density, or tumour characteristics (<T2 versus ≥T2, in situ versus invasive). In multivariate analyses, the date of the prior sMx (p = 0.001), need for arbitration (p = 0.001) and image quality (p < 0.001) remained significantly associated with the reclassification. Conclusion: This retrospective review reclassified 19% of the sMx as clearly visible tumours. With this, the Flemish screening programme performs in accordance with similar studies. The sMx reviewed in this study, form a valuable set of mammograms for training and further research

The contribution of individual populations to the Biolog pattern of model microbial communities

Model microbial communities consisting of 2 or 3 bacterial strains were used to validate the Biolog system as a tool for microbial community analysis. The a priori known taxonomical structure and carbon substrate utilization pattern of the separate community members allowed the detection and analysis of the contribution of the individual populations to the whole-community patterns. All the whole-community Biolog patterns were dominated by the fastest growing strain, even when this strain represented only 10% of the total inoculated cell numbers, and there was evidence that the activity of the slowest growing member of the model community was partially mask-ed by the other ones. However, differentiation of these closely related microbial communities was still possible with principal component analysis, provided that the incubation time was well chosen. The problem of choosing the right incubation time was overcome by the use of the parameters of the Gompertz equation, which was fitted to the color development in each Biolog well. These kinetic parameters were independent of the incubation time and still allowed a clear separation of the closely related model communities by means of principal component analysis. This approach is proposed as an alternative way for processing Biolog data in microbial community analysis

Modelling the color development in Biolog microtiter plates by the Gompertz function

The color development curves obtained from multiple readings of Biolog GN microtiter plates over a long incubation time were fitted to the Gompertz function. This yielded - for each sole-carbon source the incubation time independent and biologically relevant Gompertz parameters A (maximal extent of color development), mu(M) (specific color development rate) and lambda (lagtime). To evaluate the applicability of the model, the coefficients of determination, the residuals, the biological significance of the parameters, the stability of the parameter estimates and the predicting power of the model were determined. For the pure strains Vibrio alginolyticus and Pseudomonas fluorescens the model passed all the criteria. For the model community consisting of a mixture of 9 strains, all criteria were met for almost all the oxidized carbon sources. However, a high amount of measuring points in the color development curve is necessary (preferably >20) and the reading frequency needs to be the highest in the lagphase and the exponential phase to ensure a high stability and predictability of the estimates of mu(M) and lambda, especially when the color develops very rapidly in the wells. For a few carbon sources the Gompertz model was not appropriate, as the color development curve showed clearly 2 tiers. However, it is substantiated that the second tier may be eliminated from the time series, which allowed the model again to pass all the criteria. Finally, comparison of Biolog fingerprints of environmental samples was made with principal component analysis of the estimated Gompertz parameters for each carbon source. It is shown that this approach is practicable and may yield consistent results for environmental microbial community analysis