Are all chromosome microarrays the same? What clinicians need to know.

Microarray testing is the recommended first-tier diagnostic test for women who undergo invasive prenatal diagnostic procedures. It is well-established that microarray analysis provides information regarding copy number for changes (or copy number variants, CNVs) that may be below the resolution level of standard chromosome analysis, and that such CNVs are not related to maternal age. What may not be appreciated by ordering providers, however, are the technical differences among laboratories with respect to the established laboratory cutoff values for reporting, the definition of targeted versus nontargeted regions, and how these differences may affect the interpretation and reporting of findings which, in turn, affects counseling and possible follow-up testing of family members. Here, we provide a detailed explanation of these technical factors and clarify how they practically impact diagnostic results.