Chromosomal aberration diagnostic yield diagnosed with chromosomal microarray analysis in Latvia in 2019 and 2020

Chromosomal microarray analysis (CMA) is a molecular cytogenetic diagnostic method which can be used to detect constitutional chromosomal aberrations such as microdeletion and microduplication. Microdeletion or microduplication is defined when chromosomal deletion or duplication is smaller than 5 million base pairs (5Mb). CMA offers a diagnostic yield of 15%-20%. Indications for CMA testing are dysmorphic features, unexplained psychomotor developmental delay, autism spectrum disorders and multiple congenital anomalies. The aim of this study was to assemble CMA results, gather data about what type of chromosomal aberrations were found in Latvia and compare if our diagnostic yield corresponds to data given in scientific literature. The study was conducted in Children’s Clinical University Hospital. All data from April 2019 till September 2020 about CMA results were gathered and analysed with IBM SPSS software. During this period CMA was performed in 156 cases. 83.3% were patients and 16.7% were their relatives. The mean age was 9 years and 6 months. From all respondents 55.8% were male and 44.2% were female. Our diagnostic yield was 33.3%. From all chromosomal aberrations 7.1% were variants of uncertain significance, 8.3% were complex variants, 1.9% were benign variants and pathogenic or likely pathogenic microdeletions and microduplications were found in 16%. From all microdeletions and microduplications 16p11.2 microdeletion was the most frequent in 32%, and 22q11.2 was the second most frequent in 24%. From all tested patient relatives 42.3% were positive for chromosomal aberrations and 72.7% from these aberrations were a match with patient results. Our diagnostic yield in Latvia was much higher (33.3%) than in scientific literature. One can speculate that it is higher because of narrowly selected indications for CMA testing. The most frequent chromosomal aberration during this period was 16p11.2 microdeletion.