Microarray is a DNA based technology for scanning of the entire genome using specially designed chips. These microarray chips are available in a variety of dimensions and configurations. The quality of chip used has a very significant bearing on the quality of analysis and reporting. It is like using a 3 megapixel camera vs. a 26 megapixel camera to capture an image. In a picture captured with high megapixel camera, you can be very sure about detecting an object, its size, dimensions etc., whereas if picture hazy and pixelated like from a low megapixel camera, you cannot be sure of completely ruling out the presence or absence of any object and smaller objects may not be detected at all. Similarly, when you opt for a microarray tests, you should know that not all microarrays are same. Here is a broad comparison of various microarrays available for clinical diagnostics:
|PARAMETERS||HIGH RESOLUTION MICROARRAY||LOW RESOLUTION MICROARRAY||ULTRA LOW RESOLUTION MICROARRAY|
|Copy Number Markers||~ 2,600,000 Markers||~ 700,000 to 800,00 Markers||Less than 3,00,000 Markers|
|SNP Markers||~ 7,50,000||~ 2,00,000||Info not available|
|Marker Spacing||Dense and evenly spaced across the genome||Widely spaced across the genome||Extra wide with uneven placement across the genome|
|Gene Coverage||98 to 100%||70-80%||Less than 50%|
|Diagnostic Implication||Best option amongst the available technologies. One can be assured about detection or ruling out of ALL micro deletion /duplication syndromes. Mosaicism and UPD can be detected.||Reasonable coverage, can detect several relatively larger deletion/duplication syndrome. However, a normal result cannot completely rule out ALL micro-deletions /duplications. Mosaicism may be detected for anueploidies only.||Useful for only detecting aneuploidy – gain or loss of entire chromosome. Cannot detect mosiacism. Hence a normal report should be followed up with a higher resolution array.|
|Recommended Use||Recommended for both prenatal and postnatal diagnosis||Recommended for ruling out a relatively larger deletion/duplication syndrome in prenatal and postnatal||Not recommended for diagnostic purpose except in select cases to detect aneuploidy and where cytogenetic testing is not possible.|
|Advantages in case of Prenatal Testing||Maternal Cell Contamination (MCC) is ruled out.||Maternal Cell Contamination (MCC) cannot be ruled out.||Not available or Recommended for Prenatal Samples|
KEY QUESTION to ask in case of Microarrays – Are you getting a bio-informatics/software output or a clinical interpretation. The former is generated by the computer, while the latter is done a by a clinical and certified geneticist who can perform genotype-phenotype correlation. Clinical interpretation is essential to ensure accurate reporting of the results.
* Information is compiled from various published sources, technical documents and clinical experience of geneticists. The main aim of the comparison is to educate the doctors and patients. There is no intention to endorse or oppose any particular product, company or brand.
1. Prices mentioned are indicative and subject to change. Check for exact prices while ordering.