Table 1.

Overview of methods for diagnosing Williams syndrome

Method	Current Advantages	Current Disadvantages
Available methods
Microsatellite markers	Low cost	May be uninformative Need of trio sample
Multiplex ligation-dependent probe amplification	Low cost Highly effective Possibility of detecting other microdeletions/duplications (as determined by probe coverage)	Requires ordering provider to suspect WS to order correct probe
Fluorescence in situ hybridization	High sensitivity May detect translocations (depending on availability of probe coverage)	Higher cost False negative for smaller deletions Not possible to determinate deletion size Requires ordering provider to suspect WS to order correct probe
Chromosomal microarray	High positivity Able to determinate deletion size Able to determine CNVs elsewhere in genome. Ordering provider does not need to suspect WS to order this test	Highest cost of currently available tests Cannot detect balanced translocation/inversion
Emerging methods
Noninvasive prenatal testing	Prenatal diagnosis of aneuploidies and large deletions or duplications	Low resolution (detects deletions >3 Mb)
Facial recognition software	Cost varies with some free software available online	Diagnosis is limited by number of photographs available in database May have different efficacy based on race or ethnicity of patient
Whole-exome sequencing	Deletion detection performed in research settings	Currently used clinically for single-nucleotide variants in most cases High cost Lowest accuracy for deletion detection
Whole-genome sequencing	Combined single-nucleotide variant and CNV or structural variant detection performed in research settings	High cost, slow turnaround in some settings

WS, Williams syndrome; CNV, copy number variation; Mb, million base pairs