Visual classification of banded human chromosomes ii. classification and karyotyping of integrated density profiles

Visual classification and karyotyping of 897 integrated density profiles generated from straight and non-overlapping chromosomes from 22 trypsin-banded metaphases of average quality was carried out and evaluated. The results were compared with visual classification of photographic prints of the same 897 chromosomes. The experiments were carried out by one observer. About 5% errors were made in classification of isolated profiles; 0-5% errors were made in karyotyping profiles and about 3% errors were made in classification of isolated chromosome prints. The reason for the small error rate obtained by karyotyping profiles as compared to the error rate when classifying isolated profiles was assumed to be the use of a priori knowledge of the composition of (normal) metaphases and the possibility of making appropriate comparisons between the individual profiles within the metaphase. Comparison between classification of isolated prints and of profiles showed different error patterns on the basis of which it was assumed that prints constitute a better basis for visual classification than profiles. The results seemed to indicate two ways of improving computer classification of banded chromosomes: (1) information of value in the chromosomes (band pattern, shape etc.) should be extracted from the digitized chromosome image in a manner superior to the simple integration by which profiles are produced; (2) computer karyotyping should simulate the human method, thus taking advantage of a priori knowledge of the composition of the metaphases and being able to make appropriate comparisons between individual chromosomes.