Table 1. A proposal for a generic classification of array findings.

Finding category	Subcategory	Definition and/or subclasses	Examples
Pathogenic for the proband (ie, fetus)	Causative findings	Pathogenic finding explaining the phenotype or matching the indication	•22q11 microdeletion in a proband with a tetralogy of Fallot •Trisomy 21 in a fetus referred for cytogenetic testing due to an abnormal first trimester screening (1:20 risk for Down syndrome) • Mosaic terminal duplication 2q31.1q37.3 in a child with ASD (detected on B-Allelic frequency plot, not detected with routine karyotyping and on LogR ratio plot)22 • UPD (7) in a proband with failure to thrive22
	Unexpected diagnoses	Pathogenic findings NOT explaining the phenotype or NOT matching the indication. (a) early-onset treatable diseases (b) early-onset untreatable diseases (c) late-onset treatable diseases (d) late-onset untreatable diseases	(a) a deletion in band 10q11.21 including RET gene associated with multiple endocrine neoplasia IIA (b) DMD deletion in a male fetus referred for prenatal diagnosis because of an abnormal first trimester screening (c) a deletion in CHEK2 associated with a moderately increased risk of breast cancer and risk of other cancers in a proband with severe global developmental delay13 (d) microdeletion of 17p12 (PMP22 gene) associated with a hereditary neuropathy with liability to pressure palsies (HNPP)
	Susceptibility loci	Variants associated with neurodevelopmental disorders, but of extreme phenotypic heterogeneity and/or variable expressivity.20	16p12.1 deletion in a patient with developmental delay19
VOUS (variants of unknown clinical significance)	—	(a) potentially pathogenic (without ‘enough' evidence)1, 20 (b) truly VOUS (unknown significance)1 (c) likely benign (without ‘enough' evidence for benign)1
Benign findings	—	(a) benign (found in many healthy individuals)1 (b) polymorphic (found in >1% of the general population)1
Status for recessive diseases	—	Comprehensive reporting of heterozygous recessive mutations is not recommended. However, carrier status in case of a well-characterized recessive disorder with a reasonably high population frequency and/or with clinical features consistent with the patient's reason for referral, may be considered for disclosure.21	Deletion of CFTR gen
Incidental findings	—	Abnormalities found by chance, unintentionally, in parents of probands	Mosaic Turner syndrome discovered on B-allelic frequency plot during quality control of the array profile of a pregnant woman referred for prenatal diagnosis due to foetal ultrasound abnormalities

Examples without references refer to clinical examples from our own center.