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Stuttering via the NAGPA Gene

Summary and Pricing

Test Method

Exome Sequencing with CNV Detection
Test Code Test Copy GenesTest CPT Code Gene CPT Codes Copy CPT Codes Base Price
NAGPA 81479 81479,81479 $990
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
11503NAGPA81479 81479,81479 $990 Order Options and Pricing

Pricing Comments

Our favored testing approach is exome based NextGen sequencing with CNV analysis. This will allow cost effective reflexing to PGxome or other exome based tests. However, if full gene Sanger sequencing is desired for STAT turnaround time, insurance, or other reasons, please see link below for Test Code, pricing, and turnaround time information. If the Sanger option is selected, CNV detection may be ordered through Test #600.

An additional 25% charge will be applied to STAT orders. STAT orders are prioritized throughout the testing process.

Click here for costs to reflex to whole PGxome (if original test is on PGxome Sequencing platform).

Click here for costs to reflex to whole PGnome (if original test is on PGnome Sequencing platform).

The Sanger Sequencing method for this test is NY State approved.

For Sanger Sequencing click here.

Turnaround Time

3 weeks on average for standard orders or 2 weeks on average for STAT orders.

Please note: Once the testing process begins, an Estimated Report Date (ERD) range will be displayed in the portal. This is the most accurate prediction of when your report will be complete and may differ from the average TAT published on our website. About 85% of our tests will be reported within or before the ERD range. We will notify you of significant delays or holds which will impact the ERD. Learn more about turnaround times here.

Targeted Testing

For ordering sequencing of targeted known variants, go to our Targeted Variants page.


Genetic Counselors


  • Jana Paderova, PhD

Clinical Features and Genetics

Clinical Features

Stuttering (also called stammering) is speech characterized by frequent repetition or prolongation of sounds, syllables, or words or by frequent hesitations or pauses that disrupt the rhythmic flow of speech. Stuttering affects ~1% of the population and has a mean onset around 30 months of age (Yairi et al. J Speech Hear Res 35:782-788, 1992). Stuttering often resolves spontaneously before adulthood, particularly in females. In rare cases, stuttering can occur in adulthood as a result of brain injury (Fawcett. CNS Spectrums 10:94-95, 2005) or drug use (Krishnakanth et al. Prim Care Companion J Clin Psychiatry 10:333-334, 2008). Secondary behaviors, such as eye blinking or other involuntary head movements, are not uncommon (Prasse and Kikano. Am Fam Physician 77:1271-1276, 2008).


Variants in the gene NAGPA have been associated with stuttering (Kang et al. N Engl J Med 362:677-685, 2010). NAGPA encodes N-acetylglucosamine-1-phosphodiester alpha-N-acetylglucosaminidase (commonly known as the “uncovering enzyme”), a protein involved in the lysosomal enzyme-targeting pathway. Two missense and one frameshift variant near the 3’ end of the gene were reported. Affected individuals were heterozygous or homozygous for the variants. Penetrance of the variants does not appear to be complete. Variants in the GNPTAB and GNPTG genes, also involved in the lysosomal enzyme-targeting pathway, were similarly reported in stuttering patients. PreventionGenetics offers testing of all three genes.

Clinical Sensitivity - Sequencing with CNV PGxome

Kang et al. 2010 reported that 25 of 393 patients (6 %) had variants in one of three genes (GNPTAB, GNPTG, and NAGPA). About one third of the 25 patients had variants in NAGPA.

Testing Strategy

This test provides full coverage of all coding exons of the NAGPA gene plus 10 bases of flanking noncoding DNA in all available transcripts along with other non-coding regions in which pathogenic variants have been identified at PreventionGenetics or reported elsewhere. We define full coverage as >20X NGS reads or Sanger sequencing. PGnome panels typically provide slightly increased coverage over the PGxome equivalent. PGnome sequencing panels have the added benefit of additional analysis and reporting of deep intronic regions (where applicable).

Dependent on the sequencing backbone selected for this testing, discounted reflex testing to any other similar backbone-based test is available (i.e., PGxome panel to whole PGxome; PGnome panel to whole PGnome).

Indications for Test

All stuttering patients are candidates for this test, although it is expected that test yield will be higher for patients with a family history of stuttering or speech characterized by more than 4% stuttering dysfluencies, as measured by instruments such as the Stuttering Severity Instrument, 3rd Edition (Riley Stuttering Severity Instrument for Children and Adults. 3rd ed. Los Angeles: Western Psychological Services 1980).


Official Gene Symbol OMIM ID
NAGPA 607985
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT


Name Inheritance OMIM ID
Stuttering, Familial Persistent, 2 609261


  • Fawcett, R. G. (2005). "Stroke-associated acquired stuttering." CNS Spectr 10(2): 94-5. PubMed ID: 15685118
  • Glyndon D. Riley (1980). "Stuttering Severity Instrument for Children and Adults.".
  • Kang, C., et.al. (2010). "Mutations in the lysosomal enzyme-targeting pathway and persistent stuttering." N Engl J Med 362(8): 677-85. PubMed ID: 20147709
  • Krishnakanth, M., et.al. (2008). "Clozapine-induced stuttering: a case series." Prim Care Companion J Clin Psychiatry 10(4): 333-4. PubMed ID: 18787667
  • Prasse, J. E., Kikano, G. E. (2008). "Stuttering: an overview." Am Fam Physician 77(9): 1271-6. PubMed ID: 18540491
  • Yairi, E., Ambrose, N. (1992). "Onset of stuttering in preschool children: selected factors." J Speech Hear Res 35(4): 782-8. PubMed ID: 1405533


Ordering Options

We offer several options when ordering sequencing tests. For more information on these options, see our Ordering Instructions page. To view available options, click on the Order Options button within the test description.

myPrevent - Online Ordering

  • The test can be added to your online orders in the Summary and Pricing section.
  • Once the test has been added log in to myPrevent to fill out an online requisition form.
  • PGnome sequencing panels can be ordered via the myPrevent portal only at this time.

Requisition Form

  • A completed requisition form must accompany all specimens.
  • Billing information along with specimen and shipping instructions are within the requisition form.
  • All testing must be ordered by a qualified healthcare provider.

For Requisition Forms, visit our Forms page

If ordering a Duo or Trio test, the proband and all comparator samples are required to initiate testing. If we do not receive all required samples for the test ordered within 21 days, we will convert the order to the most effective testing strategy with the samples available. Prior authorization and/or billing in place may be impacted by a change in test code.

Specimen Types

Specimen Requirements and Shipping Details

PGxome (Exome) Sequencing Panel

PGnome (Genome) Sequencing Panel

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View Ordering Instructions

1) Select Test Method (Platform)

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2) Select Additional Test Options

No Additional Test Options are available for this test.

Note: acceptable specimen types are whole blood and DNA from whole blood only.
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