What tests should be performed on a newborn with suspected Prader-Willi syndrome?

For a newborn suspected of having Prader-Willi syndrome, the recommended tests include high-resolution banding and fluorescent in situ hybridization (FISH). This choice is correct because Prader-Willi syndrome is often characterized by the absence of paternal contributions in the 15q11-q13 region, which can be detected through these techniques.

High-resolution banding allows for the detection of chromosomal deletions and other structural abnormalities at a more detailed level than standard karyotyping, making it a valuable tool in identifying changes associated with Prader-Willi syndrome. FISH is particularly useful as it can specifically target regions of interest on chromosomes, enabling the identification of deletions or duplications of the 15q11-q13 chromosomal region that are common in this syndrome.

In contrast, standard karyotyping lacks the resolution to identify smaller deletions that may be present. Microscopic analysis alone does not provide the necessary chromosomal specificity required for accurate diagnosis. While DNA sequencing could be beneficial in some genetic conditions, it is not typically the first-line approach for diagnosing Prader-Willi syndrome given that the primary abnormalities can be detected through the aforementioned methods. Hence, high-resolution banding and FISH are the most suitable tests for confirming a diagnosis in this