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HelpTest Code 1STT1 First Trimester Maternal Screen, Serum
Reporting Name
First Trimester Maternal ScreenPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Useful For
Prenatal screening for trisomy 21 (Down syndrome) and trisomy 18
Method Name
Immunoenzymatic Assay
Ordering Guidance
This test does not screen for neural tube defects. If risk assessment for neural tube defects is desired, collect specimen between 15 weeks, 0 days and 22 weeks, 6 days of gestation for an alpha-fetoprotein single marker screen; order MAFP1 / Alpha-Fetoprotein (AFP), Single Marker Screen, Maternal, Serum.
QUAD screening (QUAD1 / Quad Screen [Second Trimester] Maternal, Serum) is not recommended following first-trimester screening.
Necessary Information
Approval to send specimen for first-trimester screening is required and may take up to 5 business days to complete. Nuchal translucency (NT) measurements are only accepted from NT-certified sonographers. Do not send specimen to Mayo Clinic Laboratories if the sonographer is not NT-certified or before completing the application process. See Maternal Screening: Sonographer Approval Process link or complete the NT/CRL Data for First Trimester/Sequential Maternal Screening.
Specimen Required
Collection Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions: Centrifuge and aliquot serum into plastic vial within 2 hours of collection
Additional Information:
1. Blood draw and ultrasound must be completed between 10 weeks, 0 days and 13 weeks, 6 days of gestation, which corresponds to a crown-rump length (CRL) range of 31 to 80 mm.
2. Initial or repeat testing is determined in the laboratory at the time of report and will be reported accordingly. To be considered a repeat test for the patient, the testing must be within the same pregnancy and trimester, with interpretable results for the same test and both tests are performed at Mayo Clinic.
Specimen Type
SerumSpecimen Minimum Volume
0.75 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum | Refrigerated (preferred) | 7 days | |
| Frozen | 90 days | ||
| Ambient | 7 days |
Reject Due To
| Gross hemolysis | Reject |
| Gross lipemia | OK |
| Gross icterus | OK |
Reference Values
DOWN SYNDROME
Calculated screen risks <1/230 are reported as screen negative.
Risks ≥1/230 are reported as screen positive.
TRISOMY 18
Calculated screen risks <1/100 are reported as screen negative.
Risks ≥1/100 are reported as screen positive. A numeric risk for trisomy 18 risk is provided with positive results on non-diabetic, non-twin pregnancies.
An interpretive report will be provided.
Interpretation
Screen-Negative:
A screen-negative result indicates that the calculated risk is below the established cutoff of 1/230 for Down syndrome and 1/100 for trisomy 18. A negative screen does not guarantee the absence of trisomy 18 or Down syndrome. Screen-negative results typically do not warrant further evaluation.
Screen-Positive:
When a Down syndrome risk cutoff of 1/230 is used for follow-up, the first trimester maternal screen has an overall detection rate of approximately 85% with a false-positive rate of 5%. In practice, both the detection rate and false-positive rate increase with age, thus detection and positive rates will vary depending on the age distribution of the screening population.
Day(s) Performed
Monday through Friday
Report Available
4 to 6 daysTest Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
81508
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| 1STT1 | First Trimester Maternal Screen | 49086-2 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 26428 | Recalculated Maternal Serum Screen | 43995-0 |
| 601798 | Results Summary | 50679-0 |
| 26434 | Down Syndrome Screen Risk Estimate | 43995-0 |
| 26435 | Down Syndrome Maternal Age Risk | 49090-4 |
| 26436 | Trisomy 18 Screen Risk Estimate | 43994-3 |
| 26426 | PAPP-A | 48407-1 |
| 601515 | PAPP-A MoM | 76348-2 |
| 26427 | THCG | 32166-1 |
| 601516 | THCG MoM | 32166-1 |
| NT_ | NT | 49035-9 |
| 601517 | NT MoM | 49035-9 |
| NT_B | NT Twin | 49035-9 |
| 601518 | NT Twin MoM | 49035-9 |
| 26437 | Interpretation | 49588-7 |
| 26439 | Recommended Follow Up | 80615-8 |
| 26438 | Additional Comments | 48767-8 |
| 26411 | Specimen Collection Date | 33882-2 |
| 26412 | Maternal Date of Birth | 21112-8 |
| 26429 | Calculated Age at EDD | 43993-5 |
| 26413 | Maternal Weight | 29463-7 |
| 26880 | Maternal Weight | 29463-7 |
| IDD_ | Insulin dependent diabetes | 44877-9 |
| B_RCE | Patient Race | 21484-1 |
| SMKN1 | Current cigarette smoking status | 64234-8 |
| DT3 | Scan Date | 34970-4 |
| CRL1 | CRL | 11957-8 |
| CRL2 | CRL Twin | 11957-8 |
| 26430 | GA on Collection by U/S Scan | 11888-5 |
| NUMF | Number of Fetuses | 55281-0 |
| CHOR | Number of Chorions | 92568-5 |
| IVF | IVF | 47224-1 |
| PRHX | Prev Down (T21) / Trisomy Pregnancy | 53826-4 |
| INTL1 | Initial or repeat testing | 86955-2 |
| SONON | Sonographer Name | 49088-8 |
| SONOC | Sonographer Code | No LOINC Needed |
| SONOD | Sonographer Reviewer ID | 49089-6 |
| DRPH1 | Physician Phone Number | 68340-9 |
| 10358 | GENERAL TEST INFORMATION | 62364-5 |
Forms
First Trimester/Sequential Maternal Screening Patient Information (T593) is required.