Ordering Recommendation

Carrier screening or diagnostic testing for Joubert syndrome type 2 for individuals of Ashkenazi Jewish descent.

New York DOH Approval Status

This test is New York state approved.

Specimen Required

Patient Preparation
Collect

Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).

Specimen Preparation

Transport 3 mL whole blood. (Min: 1 mL)

Storage/Transport Temperature

Refrigerated.

Unacceptable Conditions

Plasma or serum. Specimens collected in sodium heparin or lithium heparin tubes. Frozen specimens in glass collection tubes.

Remarks
Stability

Ambient: 72 hours; Refrigerated: 1 week; Frozen: 1 month

Methodology

Polymerase Chain Reaction (PCR)/Fluorescence Monitoring

Performed

Tue, Fri

Reported

5-10 days

Reference Interval

By report

Interpretive Data

Background Information for Joubert Syndrome Type 2 (TMEM216), 1 Variant:
Characteristics: Joubert syndrome, type 2 is characterized by a "molar tooth sign" cerebellar and brain stem malformation, hypotonia and developmental delay. Clinical manifestations and severity of the syndrome vary.
Incidence: 1 in 34,000 in Ashkenazi Jewish individuals.
Inheritance: Autosomal recessive.
Cause: TMEM216 pathogenic variants.
Variants Tested: p.R73L (c.218G>T).
Clinical Sensitivity: 99 percent in Ashkenazi Jewish individuals; unknown in other ethnicities.
Methodology: Polymerase chain reaction (PCR) and fluorescence monitoring.
Analytical Sensitivity and Specificity: Greater than 99 percent.
Limitations: Variants other than p.R73L (c.218G>T) will not be detected. Diagnostic errors can occur due to rare sequence variations.

Compliance Category

Laboratory Developed Test (LDT)

Note

Hotline History

N/A

CPT Codes

81479

Components

Component Test Code* Component Chart Name LOINC
2013910 Joubert Syndrome Type 2, Specimen
2013911 Joubert Syndrome Type 2, Allele 1
2013912 Joubert Syndrome Type 2, Allele 2
2013913 Joubert Syndrome Type 2, Interp
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Aliases

Joubert Syndrome Type 2 (TMEM216), 1 Variant