Subjectivity in chromosome band-level estimation: a multicenter study

Chromosome band level is the primary quality indicator for G-banded metaphase chromosome analysis. Although current professional guidelines address the minimum necessary band level for constitutional studies, there is no study documenting the comparative performance of different band-level estimation methods. This study compared 5 band-level estimation methods (Stallard, Vancouver, Welborn, United Kingdom External Quality Assurance Scheme, and Ford) in a multicenter study in which 82 readers from 7 different clinical cytogenetics laboratories evaluated the same 10 karyotypes (5 from amniotic fluid and 5 from peripheral blood) by each method. There was a 94% correlation between the five band-level estimation methods. The Welborn method yielded significantly lower scores for amniotic fluid karyotypes (P < 0.01) but not for peripheral blood karyotypes (P = 0.75). The distribution of scores obtained from different readers suggests a high level of subjectivity in chromosome band–level assessment. The variation in band-level estimation did not correlate with reader experience or study center, except for readers from one laboratory, for which the distribution of scores was significantly lower (P < 0.01). The results from this study suggest that the consistent use of one method is more important than the actual method employed for monitoring karyotype quality. Genet Med 16 2, 170–175.