| Synonym(s): | Diphtheria, Gram positive rod identification, MALDI-TOF, mass spectrometry |
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| Requisition Form | G-2B |
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| Test Description | Identification confirmation of Corynebacterium diphtheriae from pure isolate specimens by MALDI-TOF, with reflex toxin testing at CDC if isolate is C. diphtheriae. |
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| Pre-Approval Needed | N/A |
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| Supplemental Information Required | If C. diphtheria is suspected, please include date of onset of symptoms and antibiotic history, if available. |
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| Supplemental Form(s) | N/A |
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| Performed on Specimens from (sources) | Human |
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| Sample/Specimen Type for Testing | Pure isolate from throat, nose, or wound |
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| Minimum Volume/Size Required | At least one viable colony of pure isolate per plate/slant) |
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| Storage/Preservation Prior to Shipping | - Maintain isolate on any agar or transport medium that supports the growth of Corynebacterium spp.
- Store refrigerated at 2°C–8°C until ready for shipping.
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| Transport Medium | Any agar or transport medium that supports the growth of Corynebacterium spp., such as blood, chocolate, trypticase soy, nutrient, brain heart infusion, heart infusion, Aimes clear gel, etc. |
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| Specimen Labeling | - At least two patient identifiers required on specimen (e.g., patient full name, date of birth, medical record number).
- Three patient identifiers are preferred.
- Patient identifiers on specimen label must exactly match identifiers on submission form. (e.g., abbreviated name on label and full name on form is not acceptable.)
- Additional DSHS Laboratory specimen labeling guidelines available online here.
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| Shipping and Specimen Handling Requirements | - Ship refrigerated at 2–8°C on cold packs for overnight delivery.
- Ship according to Dangerous Goods Regulations, IATA, and/or CFR 49.
- Category B Biological Substance, UN3373 shipping requirements apply.
- Handle as infectious agent using universal precautions.
- Triple-contain in accordance with federal shipping regulations.
- Submitters are responsible for packaging and shipping specimens according to regulatory requirements.
- Laboratory does not supply collection kits or shipping materials.
- Additional DSHS Laboratory specimen shipping guidelines online here
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| Method | MALDI-TOF (mass spectrometry), Culture |
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| Turn-around Time | 3–5 days |
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| Interferences/Limitations | - Specimen should be taken from patient prior to antimicrobial therapy.
- Organism must be viable for culture studies.
- Improper storage or shipping temperatures limit organism recovery.
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| Common Causes for Rejection | - Incorrect specimen collection methods
- Mismatch(es) between patient identifiers on G-2B submission form and specimen label
- Insufficient specimen growth
- Non-viable isolates
- Mixed culture/contamination
- Incorrect storage conditions
- Expired reagents/media/collection container
- Missing/incomplete/illegible submission form
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| Additional Information | - If C. diphtheriae is confirmed, it will be submitted (reflexed) to CDC for toxin testing.
- Diphtheria is a notifiable condition and C. diphtheriae isolates are REQUIRED to be submitted to DSH Laboratory per Texas Administrative Code (TAC) chapter 97.
- Mark the “IDEAS” box for the payor source on the G-2B submission form.
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