Interlaboratory reproducibility of a microsatellite-based typing assay for Aspergillus fumigatus through the use of allelic ladders: proof of concept  H.A. de Valk, J.F.G.M. Meis, S. Bretagne, J.-M. Costa, B.A. Lasker, S.A. Balajee, A.C. Pasqualotto, M.J. Anderson, L. Alcázar-Fuoli, E. Mellado, C.H.W. Klaassen  Clinical Microbiology and Infection  Volume 15, Issue 2, Pages 180-187 (February 2009) DOI: 10.1111/j.1469-0691.2008.02656.x Copyright © 2009 European Society of Clinical Infectious Diseases Terms and Conditions

FIG. 1 Illustration of the allelic ladders for the trinucleotide repeat markers. The numbers above the peaks correspond to the repeat numbers of each allele in these ladders. Boldface alleles in a larger font were actually included in the samples; the other alleles are the result of the formation of stutter peaks upon PCR amplification of the included alleles. (a-c) The STRAf-3A, STRAf-3B and STRAf-3C allelic ladders, respectively. Clinical Microbiology and Infection 2009 15, 180-187DOI: (10.1111/j.1469-0691.2008.02656.x) Copyright © 2009 European Society of Clinical Infectious Diseases Terms and Conditions

FIG. 2 Application of allelic ladders for calibrating short tandem repeat (STR)-based typing data among different laboratories. The example shown is for the STRAf3A marker. Sample 1 yields a principal peak of size X. Size X corresponds to an allele with 27 repeats, as can be deduced from the pre-amplified allelic ladder, which is added to another capillary with the same size standard as used with regular samples. Sample 2 yields a principal peak of size Y, which corresponds to 31 repeats. Although sizes X and Y can be very precisely reproduced within a laboratory (usually within 0.2 nt), they can be very different in another laboratory on another platform and/or using different electrophoretic conditions. Clinical Microbiology and Infection 2009 15, 180-187DOI: (10.1111/j.1469-0691.2008.02656.x) Copyright © 2009 European Society of Clinical Infectious Diseases Terms and Conditions

FIG. 3 Graphical display of the size inaccuracy for each allele in the allelic ladders obtained on different analytical platforms and with different size standards. The x-axes display the repeat number of the alleles, and the γ-axes the difference between the calculated size and the actual size as determined by sequencing. Clinical Microbiology and Infection 2009 15, 180-187DOI: (10.1111/j.1469-0691.2008.02656.x) Copyright © 2009 European Society of Clinical Infectious Diseases Terms and Conditions