Skip to main content

Guideline & FAQs

Guideline

Practice Change in Molecular Testing for Cystic Fibrosis (CF)

Effective October 2016, the second tier CF mutation panel is being performed by a new method (MiSeqDx). Read the memo from the
C&W Division of Laboratory G​enetics & Genomics. The panel has been enhanced to include 130 CF causing variants. This will apply to all BC and Yukon newborns with an elevated IRT on the first tier assay. For reference, this list of CFTR variants shows the historical mutation panel that was used by the BC Newborn Screening Lab from November 2009 to September 2016, with the comparable nomenclature for the new mutation panel effective October 2016. 

Frequently Asked Questions (FAQs)

The BC Newborn Screening Program screens for 22 disorders. More information can be found on the Disorders Screened page.

 

The disorders on the screening panel were selected by the Newborn Screening Advisory Committee of BC following an evidence-based review process. 

Factors considered in the decision process included: incidence and seriousness of the disorder, evidence of improved health outcomes with early detection, test performance (accuracy and reliability), availability of confirmatory testing and follow-up treatment. 

The Newborn Screening Advisory Committee will review the panel of screening tests periodically and recommend changes as new tests and/or information about disorders becomes available.


 

“Negative screen” for all disorders

The NBS Laboratory will send a “negative screen” report to the physician/midwife listed on the blood spot card and to the baby’s birth hospital.

"Repeat sample requested"

The NBS Laboratory will send a report to the physician/midwife listed on the blood spot card to request a repeat sample. A copy of the report will be sent to the baby’s birth hospital. 

Usual reasons are:

  • baby was less than 24 hours old at the time of collection;
  • baby was less than 1,500 grams at birth;
  • baby had a blood transfusion prior to collection of the sample; or
  • sample was unsatisfactory.

“Positive screen” for one of the disorders

A positive screen does not mean that the baby has a disorder, but only that further testing is required. Please refer to the below three questions for further information.


 

The NBS Laboratory will contact the baby’s physician/ midwife by phone to discuss the positive screen and coordinate the next steps.


Generally, the physician/midwife will be asked to contact the family to assess the clinical state of the baby and organize the repeat testing. Contact information for an appropriate specialist on-call will also be provided in cases in which there are immediate clinical concerns.

The NBS Laboratory will contact the baby’s physician/midwife with the repeat testing results as soon as they are available and will coordinate referral to the appropriate clinical specialty if the repeat results are positive.


 

Screening for cystic fibrosis and hemoglobinopathies may identify a baby that is a CF carrier or has a hemoglobinopathy trait.

It is important for the parents to know if the baby is a CF carrier or has a hemoglobinopathy trait so they can:


  • Tell their child later in life. His or her future partner can choose to have testing to identify the couple’s chances of having a baby with CF, or a clinically significant hemoglobinopathy.

  • Decide whether they wish to be tested. If the baby is a CF carrier or has a hemoglobinopathy trait, one parent is almost certainly a carrier. There is a small risk that both parents are carriers which would have implications for future pregnancies.

Resources are available to assist in counseling families with regards to these issues. Referral to the BC Medical Genetics program (see below) for genetic counseling may also be appropriate under some circumstances.


 

Pre-test counselling and testing can be done by the physician.

If parents wish additional genetic counselling, the physician may refer them to the provincial Medical Genetics Program in Vancouver (604-875-2157) oVancouver Island Medical Genetics in Victoria (250-727-4461).

Questions from physicians and nurses about carrier testing and the interpretation of results may be directed to a genetic counsellor in one of the Medical Genetics clinics listed above.


 

There are 10 secondary disorders that are not primary targets of the screening program but may be identified as “by-products” of the screening process:


  • Amino Acid Disorders
    i. Hypermethioninemia (MET)
    ii. Citrin Deficiency (CIT II)
    iii. Mild Hyperphenylalaninemia (H-Phe)
    iv. Biopterin Biosynthesis Defects (BIOPT BS)
    v. Biopterin Recycling Defects (BIOPT REC)

  • Organic Acid Disorders
    i. Cobalamin C/D (Cbl C/D)
    ii. 2-methylbutyrylglycinuria (2MBG)

  • Fatty Acid Oxidation Disorders
    i. Trifunctional Protein Deficiency (TFP)
    ii. Multiple Acyl-CoA Dehydrogenase Deficiency (MAD)

  • Hemoglobinopathies
    i. Variant Hemoglobinopathies (Var Hb)
 

Screening for MSUD, Hcy, CAH, PROP, MUT, and CbIA,B was introduced in two phases. First tier testing (phase 1) began in November 2009, and second tier testing with additional analytes (markers) was added in the fall of 2010.

The second tier tests are performed on the original blood sample when the first screen is abnormal. Second tier testing increases the:


a. sensitivity (proportion of cases detected); and
b. positive predictive value (PPV; percentage of babies with a positive screen that truly have the disorder).

For more information: Sensitivity and Positive Predictive Value Table.


 

Newborn screening is not mandatory, but it is considered “standard of care” and is recommended for all babies born in BC. Parents/legal guardian may decline screening after receiving information on the purpose and benefits of the screening (see the Informed Refusal process outlined in the guideline).

Note: A surrogate mother will not likely have completed the papers to be the legal guardian by the time blood is collected for the newborn screening tests. Consult your health authority policy and/or risk management department as to the acceptability of a surrogate mother signing the refusal form if legal documentation is not in place.


 


SOURCE: Guideline & FAQs ( )
Page printed: . Unofficial document if printed. Please refer to SOURCE for latest information.

Copyright © Perinatal Services BC. All Rights Reserved.

    Copyright © 2017 Provincial Health Services Authority.