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FASD: Assessment and diagnosis

Key points

  • The diagnosis of FASD is complex and requires a comprehensive, multidisciplinary assessment.
  • Fetal Alcohol Spectrum Disorder: Canadian Guidelines for Diagnosis are the Canadian standard for diagnosing FASD. 
  • FASD diagnosis involves:
    • a physical examination
    • a dysmorphology assessment
    • a neurobehavioural assessment
    • prenatal alcohol exposure (PAE) confirmation (a diagnosis of FAS can be made without confirmation of PAE).

Diagnostic criteria

Fetal Alcohol Spectrum Disorder: Canadian Guidelines for Diagnosis lists three FASD-related diagnoses:

  • fetal alcohol syndrome (FAS)
  • partial fetal alcohol syndrome (pFAS)
  • alcohol-related neurodevelopmental disorder (ARND).

FAS is the only FASD-related diagnosis included in the current version of the International Classification of Diseases (ICD-10). The current version of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) includes proposed criteria for neurodevelopmental disorder associated with prenatal alcohol exposure (ND-PAE) under "Conditions for Further Study."

Read the full FASD diagnostic criteria.

Physical examination and differential diagnosis

The general physical examination includes:

  • ruling out other potential causes of symptoms  
  • appropriate measurements of growth (height and weight) and occipital-frontal circumference
  • assessment of characteristic facial and other physical features
  • documentation of anomalies (e.g., cleft palate, congenital heart defects, epicanthic folds, high arched palate, poorly aligned or abnormal teeth, hypertelorism, micrognathia, abnormal hair patterning, abnormal palmar creases, skin lesions).

Other conditions that resemble FASD

There are other genetic disorders and multifactorial disorders that can lead to features that mimic those observed in among individuals with FAS and pFAS. These disorders include:

  • Aarskog syndrome
  • Bracjman-deLange or Cornelia deLange syndrome
  • Dubowitz syndrome
  • fetal anticonvulsant syndrome (includes fetal hydantoin and fetal valproate syndromes)
  • maternal phenylketonuria (PKU) fetal effects
  • Noonan syndrome
  • toluene embryopathy
  • Williams syndrome
  • other chromosome deletion and duplication syndromes.

Measurement of growth

The examination determines the presence of prenatal and postnatal growth deficiency, defined as height and weigh at or below the tenth percentile or a disproportionately low weight-to-height ratio (at or below the tenth percentile) using appropriate norms.

Other factors that influence growth such as parental size, genetic potential and associated conditions (e.g., gestational diabetes, nutritional status, illness) must also be taken into consideration.

Physical features

Characteristic facial features

The three characteristic facial features that differentiate individuals with FAS from those without FASD are:

  • short palpebral fissures, at or below the third percentile (2 standard deviations below the mean)
  • smooth or flattened philtrum, 4 or 5 on the 5-point Likert scale of the lip-philtrum guide
  • thin vermilion border of the upper lip, 4 or 5 on the 5-point Likert scale of the lip-philtrum guide.

Other physical features

Other physical features associated with FASD include:

  • hypoplastic midface
  • micrognathia
  • abnormal position or formation of the ears
  • high arched palate
  • Hypertelorism
  • epicanthic fold
  • limb and palmar crease abnormalities
  • short upturned nose.

These observations should be noted, but they do not contribute to a diagnosis.

Neurobehavioural assessment

The assessment should include:

  • hard and soft neurologic signs (including sensory motor signs)
  • brain structure (occipitofrontal circumference, magnetic resonance imaging, etc.)
  • cognition (IQ)
  • communication: receptive and expressive
  • academic achievement
  • memory
  • executive functioning and abstract reasoning
  • attention deficit/hyperactivity
  • adaptive behaviour, social skills, social communication.

The assessment should include and compare basic and complex tasks in each domain, as appropriate.

Read more about the neurobehavioral assessment.

Prenatal alcohol exposure confirmation

Confirmation of prenatal alcohol exposure (i.e., confirmation of alcohol consumption by the mother during the pregnancy) is also required for a FASD diagnosis (with the exception of an FAS diagnosis. This can be obtained through a direct interview with the mother or from other sources, such as reliable clinical observation, reports by a reliable source or medical records.

See the Addiction Toolkit for more about screening for alcohol use.

Validated tools for obtaining maternal alcohol use confirmation include:

TWEAK

T-ACE

CAGE

AUDIT

SMAST

B-MAST

Timeline Followback (TLFB).

Resources

The Tools for Primary Care Providers (developed by the Developmental Disabilities Primary Care Initiative) include a Health Watch Table–Fetal Alcohol Spectrum Disorder (FASD). This table includes a checklist of assessment and diagnosis recommendations.


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