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Neurodevelopmental disorders

Chromosomal microarray is a high resolution, genome wide screen for the detection of genetic imbalance.

  • Higher resolution and abnormality rate than karyotype/chromosome analysis
  • Detects microdeletions currently tested for by FISH

Sample requirements

To request a microarray test please send blood samples, well mixed, in EDTA (3-5ml) to Cytogenetics. Only one sample tube is required. For patients who are difficult to bleed, we will attempt to process smaller samples. Click here for the GLH Rare and Inherited Disease referral form.

Please note that blood samples in lithium heparin tubes are not required. Any lithium heparin samples for these referrals will not be processed and they will be discarded.

For parental follow up samples, however, we may still request blood specimens in both EDTA (3-5ml) and lithium heparin (1-2ml) within the probands report. This is because sometimes we need to exclude a balanced parental rearrangement by FISH or karyotype. For sample labelling, sample tube guide and referral form criteria see referral requirements.

For accurate interpretation of the array result include full clinical details of the patient and relevant family members including cytogenetic laboratory references.

Acceptance and rejection criteria

For microarray testing blood in any tube other than EDTA will not be processed. The preferred volume is larger than 1ml but for smaller volumes (>0.25ml) processing will be attempted but the test may be unsuccessful.

Referral categories

Please provide a detailed clinical description because this is required for the interpretation of results.

Microarray testing has replaced karyotype analysis for patients who fulfil some of the following criteria:

  • Developmental delay
  • Learning disability
  • Facial dysmorphism or congenital abnormalities
  • Hypotonic infant
  • Congenital heart disease
  • Behavioural problems/autistic spectrum

Please see below the phenotypes in the current Test Directory that state microarray as a testing method.

R137 – Congenital heart disease – microarray

R199 – Congenital anomalies of the kidney and urinary tract – familial

R27 – Congenital malformation and dysmorphism syndromes – microarray and sequencing (R27.2)

R28 – Congenital malformation and dysmorphism syndromes – microarray only

R29 – Intellectual disability – microarray and sequencing (R29.2)

R343 – Chromosomal mosaicism – microarray

R377 – Intellectual disability – microarray only

R69 – Hypotonic infant (R69.3)

R89 – Ultra-rare and atypical monogenic disorders

R100 – Rare syndromic craniosynostosis or isolated multisuture synostosis (R100.2)

R146 – Disorders of sex development (R146.1)

R147 – Growth failure in early childhood (R147.3)

R59 – Early onset of syndromic epilepsy (R59.2)

R83 – Arthrogryposis (R83.2)

R84 – Cerebellar anomalies (R84.2)

R86 – Hydrocephalus (R86.2)

R87 – Cerebral malformation (R87.2)


Some referrals for WGS also require an array test as well. Please see the current list below

Congenital malformation and dysmorphism syndromes


Congenital malformation and dysmorphism syndromes

R27.2 Microarray


Intellectual disability – microarray and sequencing

R29.2 Microarray


Early onset or syndromic epilepsy

R59.2 Microarray



R83.2 Microarray



R86.2 Microarray


Cerebral malformation

R87.2 Microarray


Severe microcephaly

R88.2 Microarray


Ultra-rare and atypical monogenic disorders

R89.2 Microarray


Rare syndromic craniosynostosis or isolated multisuture synostosis

R100.2 Microarray









Please refer to the Test Directory published on the NHS England website.

Some copy number changes (CNVs) may be reported as of uncertain significance and cannot be fully interpreted without investigation of parental samples. These will be requested in the report and only a targeted analysis of parental samples will be carried out with respect to the copy number change observed in the original test of the proband. Microarray may detect unexpected genetic CNVs with wider implications for other family members.

Microarray will not exclude:

  • Balanced rearrangements
  • Point mutations
  • Fragile X
  • Single gene disorders
  • Some cases of Prader-Willi or Angelman Syndrome
  • Some cases of mosaicism

Please indicate at referral if additional testing for the conditions listed above is required.

Reporting times

Please see our Target Reporting Times.


Please see our limitations of testing page.

Storage and further testing

DNA from EDTA samples is stored within Molecular Genetics indefinitely. Subsequent genetic testing can be requested at any time but may not be possible depending on the quality of the material available.

Page last updated 31/08/2023. Please note that if printed, the information is only valid on the day of printing.