2T Sequential Screen Build info

Synonyms

• 2T SEQUENTIAL SCREEN
• 2TSEQ
• LAB14342

Procedure Name

2T SEQUENTIAL SCREEN

Procedure Master Number

LAB14342

Procedure ID

186085

Clinical Info

2T Sequential Screen combines a
patient’s previous 1T Aneuploidy screen with a second trimester QUAD Screen to
test for the two most common fetal aneuploidies, trisomies 21 and 18.  2T Sequential screen measures maternal serum
AFP, Free beta hCG, Inhibin A and uE3 then combines the results with the
patients first trimester PAPP-A, nuchal translucency (NT) and nasal bone (NB -
optional).  An increased risk result
means that further screening (ultrasound, NIPT) and/or diagnostic testing
(amniocentesis) may be offered

Specimen Sources

Specimen Types

Container

Gold Top Tube

Collection Instructions

Specimen: 3mL Serum (0.5 mL min)
Specimen draw is from 15w0d to
21w6d gestation and must be before CVS or amniocentesis.
 Special Instructions:
The following Ask on Order Entry
(AOE) patient information must be provided:
1: Maternal Weight
2: Family History of ONTD
3: Valproic Acid
4: Carbamazepine
5: Insulin Dependent Diabetes
Complete information is necessary
to interpret the test. Patient information may be provided to the laboratory
using the Maternal Prenatal Screening request form (0900).

Specimen Volume

3 mL serum (0.5 mL min)

Transport Instructions

Refrigerated

Specimen Stability

6 Days Room Temperature or Refrigerated

Methodology

Time-Resolved Amplified Cryptate Emission ( TRACE)

Days Performed

Monday - Friday   TAT 1-3 Days

Performing Laboratory

Northwell health Laboratories

CPT

82105- AFP
84704- BhCG
86336- Inhibin A
82677- uE3

PDM

Only Orderable at Locations:

Results

Result Interpretation

Risk Calculation:

Each analyte level is converted into a multiple of the GA specific median (MoM) and is then adjusted based on the patient's race, weight, diabetic status, and smoking status.  The likelihood ratio for each analyte is calculated as the ratio of the probability density function in affected pregnancies divided by the probability density function for unaffected pregnancies.  Patient specific risks for Down syndrome and trisomy18 are calculated using Bayes’ rule. The prior risk, based on demographic factors, is multiplied by the likelihood ratios for each maker appropriate for the condition screened.

An interpretive risk report including the patient's analyte levels (Both first and second trimester), cut-off values and risks for trisomy 21, trisomy 18 and Open Spina Bifida will be provided.

    Down’s Syndrome (trisomy 21) Interpretation:

The risk cut-off is set equal to the mid-trimester risk of a 35 year old (1/270).  This test may detect 95% of cases with Down’s syndrome at an approximate 4.2% false positive rate. (Baer et.al.)

    Edward Syndrome (trisomy 18) Interpretation:

The risk cut-off is set equal to 1/100. This cut-off is chosen to balance the detection and false positive rates.  This test may detect 93.5% of cases with T18 at an approximate 0.5% false positive rate. (Baer et.al.)

     Open Spina Bifida Interpretation:

The MS-AFP level is converted into a multiple of the GA specific median (MoM) and is then adjusted based on the patient's race, weight, diabetic status, and smoking status. The ONTD cut-off is 2.5 MoM but is adjusted to account for the patient’s prior risk factors such as African America/Caribbean race, IDDM, twin pregnancy, family history and use of valproic acid or Carbamazepine. The interpretation is based on the patient's analyte adjusted.

AFP MoM result compared to the risk adjusted cut-off.   For more detail see 2T Maternal Serum AFP (MSAFP)

  Test Follow Up:

If the patient's risk is less than the cut-off risk the test is considered "Within Normal Range" and no further action is required. If the patient’s risk is greater than or equal to the cut-off risk the test is considered "Increased Risk". Patients at increased risk are offered detailed ultrasound, NIPT and/or diagnostic amniocentesis.

Upon receiving maternal serum screening results, all information used in the risk calculation should be reviewed for accuracy (ie, weight, diabetic status, gestational dating). If any information is incorrect, the laboratory should be contacted for recalculation of the estimated risks. ‘Within Range’ risk results typically do not warrant further evaluation. The screen results are dependent on accurate information for gestation, race, IDD, and weight. Inaccurate information can lead to significant alterations in the estimated risk.

   Disclaimers

This test was developed, and its performance characteristics determined by Northwell Health Laboratories. The test has not been cleared or approved by the U.S. Food and Drug Administration. These results do not eliminate the possibility that the pregnancy may be associated with birth defects including open spina bifida, Down syndrome, trisomy 18, trisomy 13 or other disorders not detectable by this screening test. Gestational Age is determined based on first trimester gestational age and number of days between first and second trimester blood collection dates.

   Cautions

Valid measurements of maternal serum markers cannot be made after CVS or amniocentesis. Triplet and higher order multiple pregnancies cannot be interpreted. In rare cases, some individuals can develop antibodies to mouse or other animal antibodies (often referred to as human anti-mouse antibodies [HAMA] or heterophile antibodies), which may cause interference in some immunoassays. Caution should be used in interpretation of results and the laboratory should be alerted if the result does not correlate with the clinical presentation.

Each center offering maternal serum screening to patients should establish a standard screening protocol, which provides pre- and post-screening education and appropriate follow-up for ‘Increased Risk’ results.

Forms

• Technical Bulletin:2T Sequential Screen New Test-Test Update 09-30-2024