Clinical Education Center
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- ABL Kinase Domain Mutation in CML, Cell-based
- ABO Group and Rh Type
- Acid-Fast Bacillus (AFB) Identification, Sequencing and Stain, Paraffin Block
- ADAMTS13 Activity with Reflex to ADAMTS13 Inhibitor
- Alcohol Metabolites, Quantitative, Urine
- Alpha-Globin Common Mutation Analysis
- Alpha-Globin Gene Deletion or Duplication
- Alpha-Globin Gene Sequencing
- Anti-Müllerian Hormone AssessR™
- Anti-PF4 and Serotonin Release Assay (SRA) for Diagnosing Heparin-induced Thrombocytopenia/Thrombosis (HIT/HITT)
- Antiphospholipid Antibodies
- ASCVD Risk Panel with Score
- Autoimmune Epilepsy Evaluation
- Autoimmune Diseases, Tests for
- B-cell and T-cell Clonality Assays by PCR
- B-Type Natriuretic Peptide (BNP)
- BCR-ABL1 Gene Rearrangement, Quantitative PCR
- Beta-Globin Complete
- BRCAvantage®, Ashkenazi Jewish Screen
- BRCAvantage®, Rearrangements
- BRCAvantage™, Comprehensive
- BRCAvantage™, Single Site
- CDH1 Sequencing and Deletion/Duplication
- Clostridium difficile Diagnostic Testing
- C1 Inhibitor, Protein and Functional Tests
- Calreticulin (CALR) Mutation Analysis
- Carbapenem Resistant Enterobacteriaceae Culture Screen
- Cardio IQ Lipoprotein Fractionation, Ion Mobility
- Cervical Cancer, TERC, FISH
- CFvantage® Cystic Fibrosis Expanded Screen
- Chlamydia trachomatis, TMA
- Chlamydia trachomatis/Neisseria gonorrhoeae RNA, TMA
- Chromosomal Microarray, POC, ClariSure®, Oligo-SNP
- Chromosomal Microarray, Postnatal, ClariSure® Oligo-SNP
- Chromosome Analysis and AFP with Reflex to AChE, Fetal Hgb, Amniotic Fluid
- Chromosome Analysis, Amniotic Fluid
- Chromosome Analysis, Blood
- Chromosome Analysis, Blood with Reflex to Postnatal, ClariSure® Oligo-SNP Array
- Chromosome Analysis, Chorionic Villus Sample
- Chromosome Analysis, High Resolution
- Chromosome Analysis, High Resolution with Reflex to Postnatal, ClariSure® Oligo-SNP Array
- Chromosome Analysis, Mosaicism
- Chromosome Analysis, Neonatal Blood
- Chromosome Analysis, Sister Chromatid Exchange
- Chromosome Analysis, Tissue
- Chromosome DEB Assay for Fanconi anemia
- Chronic Lymphocytic Leukemia (CLL) - Diagnostic and Prognostic Testing
- Culture, Fungus
- Culture, Urine, Routine
- Cystic Fibrosis Screen
- Cytomegalovirus (CMV) and Epstein Barr Virus (EBV) PCR
- D-Dimer, Quantitative
- Dementia, Secondary Causes
- Dengue Virus Testing
- Diabetes Risk Panel with Score and Cardio IQ® Diabetes Risk Panel with Score
- Drug Testing, General Toxicology (Blood, Urine, or Serum)
- Drug Toxicology Alcohol Metab, QN, Oral Fluid
- Drug Toxicology Monitoring, Oral Fluid Testing
- Factor V (Leiden) Mutation Analysis
- Familial Mediterranean Fever Mutation Analysis
- First Trimester Screen, hCG
- First Trimester Screen, Hyperglycosylated hCG (h-hCG)
- FISH, Angelman
- FISH, MET Amplification
- FISH, Myeloma, 17p-, rea 14q32 with Reflexes
- FISH, Prader-Willi
- FISH, Prenatal Screen
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- HCV Genotyping
- Helicobacter pylori (H pylori) Antibody Discontinuation
- Heparin, Anti-Xa
- Hepatitis B Surface Antibody, Quantitative
- Hepatitis C Antibody with Reflex to HCV RNA, PCR with Reflex to Genotype
- Hepatitis C Viral RNA Genotype 1 NS5A Drug-resistance
- Hepatitis C Viral RNA Genotype 3 NS5A Drug Resistance
- Hepatitis C Viral RNA NS3 Drug Resistance
- Hepatitis C, RNA, Quantitative, PCR
- Hereditary Cancer Panels: MYvantageTM Hereditary Comprehensive Cancer Panel and GIvantageTM Hereditary Colorectal Cancer Panel
- Hereditary Hemochromatosis DNA Mutation Analysis
- Herpes Simplex Virus (HSV) Type-Specific IgG Antibodies
- Herpes Simplex Virus Type 2 (HSV-2) IgG Inhibition, ELISA
- HIV-1 Coreceptor Tropism, Proviral DNA
- HIV-1 Coreceptor Tropism, Ultradeep Sequencing
- HIV-1 Integrase Genotype
- HIV-1/2 Antigen and Antibodies, Fourth Generation, with Reflexes
- HPV mRNA E6/E7
- Influenza A and B Antigen, Immunoassay
- Influenza Type A and B Antibodies
- Insulin, Intact, LC/MS/MS
- Integrated Screen, Part 1
- Integrated Screen, Part 2
- Intrinsic Factor Blocking Antibody
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- Maternal Serum AFP
- Melanoma, BRAF V600E and V600K Mutation Analysis, THxID®
- Metanephrines, Fractionated, Free, LC/MS/MS, Plasma
- Methylenetetrahydrofolate Reductase (MTHFR), DNA Analysis
- Microalbumin (Urinary Albumin Excretion)
- Pain Management and CYP2D6/CYP2C19
- Pain Management, Naltrexone, Quantitative, Urine
- Partial Thromboplastin Time, Activated (aPTT)
- Penta Screen
- PIK3CA Mutation Analysis
- PNH with FLAER (High Sensitivity)
- Prothrombin Time with INR
- PTH, Intact and Calcium
- Streptococcus pneumoniae (Pneumococcal) Antibody Tests
- Saccharomyces cerevisiae Antibodies (ASCA) (IgG, IgA)
- Sequential Integrated Screen, Part 1
- Sequential Integrated Screen, Part 2
- Serum Integrated Screen, Part 1
- Serum Integrated Screen, Part 2
- Serum Pregnancy Tests
- Sickle Cell Screen
- Stepwise, Part 1
- Stepwise, Part 2
- SureSwab® Trichomonas vaginalis RNA, Qualitative TMA
- SureSwab®, Candidiasis, PCR
- TP53 Sequencing and Deletion/Duplication
- T4, Free
- Tamoxifen and Metabolites, LC-MS/MS
- Testosterone Testing
- Total Testosterone, LC/MS/MS
- Triple Screen
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First Trimester Screen, hCGTest code(s) 16145, 16968(NY)
Question 1. My patient had a negative First Trimester Screen, hCG test. What should I do next?
A negative screen means it is unlikely the fetus has either Down syndrome or trisomy 18. But a negative screen does not guarantee the birth of a healthy baby. The demographic information provided at the time of testing is used in calculating the patient’s Down syndrome and trisomy 18 risk. Please check the demographic information to ensure accuracy of calculated results.
The first trimester screening test screens only for Down syndrome and trisomy 18. Guidelines recommend neural tube defect screening be performed in the second trimester.1 The Maternal Serum AFP test (test code 5059) is available for this purpose.
Question 2. My patient’s result was screen positive for Down syndrome. What should I do next?
A positive Down syndrome screen result means there is an increased risk for the fetus to be affected with Down syndrome or other chromosome abnormalities. The demographic information provided at the time of testing is used in calculating the patient’s Down syndrome and trisomy 18 risk. Please check the demographic information to ensure accuracy of calculated results.
Guidelines recommend counseling women with a positive screening test. Such counseling may include a discussion of the significance of the screening results and diagnostic testing options (eg, chorionic villus or amniocentesis testing) and/or noninvasive prenatal screening (NIPS; test code 92777 or 91933[NY]). Guidelines do not recommend repeating Down syndrome positive screening tests.
Question 3. My patient’s result was screen positive for trisomy 18. What should I do next?
A positive trisomy 18 result means there is an increased risk for the fetus to be affected with trisomy 18 or other chromosome abnormalities. The demographic information provided at the time of testing is used in calculating the patients Down syndrome and trisomy 18 risk. Please check the demographic information to ensure accuracy of calculated results.
Guidelines recommend counseling women with a positive screening test. Such counseling may include a discussion of the significance of the screening results and diagnostic testing options (eg, chorionic villus or amniocentesis testing) and/or noninvasive prenatal screening (NIPS; test code 92777 or 91933[NY]). Guidelines do not recommend recalculating incorrect EDD/gestational age or repeating trisomy 18 positive screening tests.
Question 4. The report indicates a different gestational age than what I determined. How is the gestational age calculated?
The gestational age is calculated from the crown rump length (CRL) provided, using criteria from the Fetal Medicine Foundation. If the CRL is not provided, the gestational age is derived from the expected date of delivery (EDD) and the collection date provided and is an exact calculation by calendar days. Gestational wheels may be inaccurate by several days or more.
Note that the gestational age is reported in decimal weeks. For example, 11 weeks 4 days is reported as 11.6 weeks.
Question 5. When is it appropriate to change the gestational age or estimated date of delivery (EDD) on a maternal serum screen result report?
It is appropriate to change the gestational age or EDD when the data used for screening are substantially above or below that determined by ultrasound. In case of a positive screen for trisomy 18, however, guidelines recommend against changing the gestational age or EDD (see Question 3.)
The earliest EDD calculated by ultrasound should be used for dating purposes.2 An ultrasound derived EDD is most accurate when determined in the first trimester. Accuracy decreases with advancing gestational age. For example, accuracy of an ultrasound EDD is ±7 days in the first trimester and ±10 days in the second trimester.
If a first trimester ultrasound EDD is available and the gestational age used for screening is within the EDD ±7 days, the gestational age should not be changed for screening purposes. If the gestational age used for screening is outside the ultrasound EDD range, it may be appropriate to change the gestational age used for screening.
If you want to change the EDD/gestational age used for a specific patient’s screening test, please contact your local Quest Diagnostics laboratory or call Quest Genomics Client Services at 866-GENE-INFO. If the revised gestational age is between 10.0 to 13.9 weeks gestation, we can calculate and report new risks. If the revised gestational age is <10.0 weeks, we cannot calculate new risks. Consider submitting a second specimen for screening, collected when the patient is between 10.0 to 13.9 weeks gestation. If the revised gestational age is >13.9 weeks gestation, we cannot calculate new risks, and a more accurate risk assessment cannot be provided. Consider submitting a second specimen for second trimester screening (ie, Penta Screen or Quad Screen) when the patient is between 15.0 to 22.9 weeks gestation (preferably 16 to 18 weeks).
Question 6. My patient has a family history of Down syndrome or trisomy 18. What impact does this have on these results?
Please call Quest Genomics Client Services at 866-GENE-INFO to discuss this case with a genetic counselor. Documentation of the abnormality in the family may enable a more specific risk assessment or indicate whether additional studies should be performed.
Question 7. My patient had a normal maternal serum screen, but her risk for Down syndrome was higher than her age-related risk. How do I explain this?
A cutoff of 1 in 270, the risk of a 35-year old, is used to determine if a pregnancy is screen negative or screen positive for Down syndrome. This cutoff is used regardless of the patient’s age, since it’s the historical cutoff for offering diagnostic testing (amniocentesis).
When counseling a pregnant patient, it may be helpful to compare her age-related risk (ie, pre-test risk) with her screen-derived risk (post-test risk) and the general population risk (1 in 600-800 live births). This allows the patient and her partner to better understand her risk of carrying a Down syndrome-affected fetus and to weigh it against the risks and consequences of amniocentesis.
Question 8. What does a low PAPP-A result mean and is there a follow-up test?
There is no consensus as to exactly what constitutes a low PAPP-A value in first trimester screening. However, low PAPP-A levels have been associated with low birth weight, reduced fetal growth, hypertension, pre-eclampsia, pre-term labor, and fetal demise. When a physician considers a patient’s PAPP-A to be low, he/she usually treats her as if she has a high risk pregnancy and follows her more closely as the pregnancy progresses.
Question 9. What is a Down syndrome pseudo-risk in a twin gestation? Why don't we give twin-specific risks?
Prenatal screening in twin pregnancies is complex. The serum markers can be measured in a patient with a twin gestation and then divided by corresponding medians for unaffected singleton pregnancies to calculate multiple of medians (MoMs) which are then adjusted for twins in order to provide a pseudo-risk for Down syndrome. This calculation accounts for the presence of two fetuses, and also takes into account the nuchal translucency measurement of each specific fetus. The result is a pregnancy-specific pseudo-risk, rather than a fetus-specific risk.
Question 10. In a twin gestation, why is there no risk assessment reported for trisomy 18?
Prenatal screening in twin pregnancies is complex. A trisomy 18 risk assessment is not calculated for twin gestations due to insufficient screening marker data from affected twin pregnancies.
- ACOG Committee on Practice Bulletins. ACOG Practice Bulletin No. 77: screening for fetal chromosomal abnormalities. Obstet Gynecol. 2007;109:217-227.
- American College of Obstetricians and Gynecology. Committee Opinion No 611: Method for estimating due date. Obstet Gynecol.2014;124:863-866.