Parental Understanding of Newborn Screening for Cystic Fibrosis After a Negative Sweat-Test

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Cystic Fibrosis After a Negative Sweat-Test

WHAT’S KNOWN ON THIS SUBJECT: The current standard of care includes informing women about prenatal testing and newborn screening for cystic fibrosis and providing genetic counseling to parents whose child is referred for sweat-testing. Despite counseling, early data identified some persistent confusion about residual risk.

WHAT THIS STUDY ADDS: Prenatal discussions about carrier testing and newborn screening for cystic fibrosis are not routine. Parental anxiety about abnormal results from a screen is decreased after speaking to a genetic counselor when scheduling the sweat test. Despite counseling, residual risk continues to be poorly understood.


BACKGROUND:Newborn screening for cystic fibrosis (CF) in Illinois uses an immunoreactive trypsinogen/DNA methodology; most false-positive results identify unaffected carriers.

METHODS:Parents whose child received a negative result from the sweat test after a positive newborn screening for CF were surveyedⱖ6 weeks later by telephone. All parents received genetic counseling while waiting for the sweat-test results.

RESULTS:A total of 90 parents participated. Overall knowledge of CF was high (78%), but the ability to understand the CF screening results was mixed. Although 94% of the parents understood that their child did not have CF, only 79% (62 of 78) of participants whose child had a mutation knew their child was definitely a carrier, and only 1 of 12 parents whose child had no mutation understood that the child may be a carrier. Respondents stated that most relatives were not interested in genetic testing. Both parents had been tested in only 13 couples. Fewer than half (36 of 77 [47%]) of the untested couples expressed interest in genetic testing. Although most participants were satisfied with the process, parents expressed frustration because of the lack of prospective newborn screening discussions by prenatal and pediatric providers and lack of knowledge and sensitivity by those who initially notified them of the abnormal newborn screening results. Speaking to a genetic counselor when scheduling the sweat test decreased anxiety for many parents (53 of 73 [73%] were “very worried” at notification versus 18 of 73 [25%] after scheduling;P⬍.001).

CONCLUSIONS:Parental knowledge about CF is high, but confusion about the child’s carrier status and the concept of residual risk persist despite genetic counseling. Relatives express low interest in carrier testing.Pediatrics2011;127:276–283

AUTHORS:Colleen Walsh Lang, BA, BS,aSusanna A. McColley, MD,b,cLucille A. Lester, MD,dand Lainie Friedman Ross, MD, PhDe

aMD-PhD program, Washington University in St Louis, St Louis,

Missouri;bDivision of Pulmonary Medicine, Cystic Fibrosis

Center, Children’s Memorial Hospital, Chicago, Illinois;

cDepartment of Pediatrics, Northwestern University Feinberg

School of Medicine, Chicago, Illinois; anddSection of Pediatric

Pulmonary Medicine, Department of Pediatrics, Cystic Fibrosis Center, Universtiy of Chicago, Chicago, Illinois, and

eDepartments of Medicine, Pediatrics, and Surgery, MacLean

Center for Clinical Medical Ethics, University of Chicago, Chicago, Illinois


cystic fibrosis, false-positive, newborn screening, genetic counseling, genetic testing, heterozygote detection, residual risk, sweat test, anxiety

ABBREVIATIONS NBS—newborn screening CF—cystic fibrosis

IRT—immunoreactive trypsinogen


Accepted for publication Nov 1, 2010

Address correspondence to Lainie Friedman Ross, MD, PhD, Department of Pediatrics, University of Chicago, 5841 S Maryland Ave, MC 6082, Chicago, IL 60637. E-mail:

PEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, 1098-4275).

Copyright © 2011 by the American Academy of Pediatrics


Newborn screening (NBS) for cystic fi-brosis (CF) began in the United States in Colorado and Wisconsin in the early 1980s using a 2-stage immunoreactive trypsinogen (IRT) screening methodol-ogy.1,2 Children with an elevated IRT

had a second sample collected. If the IRT remained elevated, they were re-ferred for a diagnostic sweat test. With the discovery of the␦ F508 mutation of the CF gene in 1988, Wisconsin switched to an IRT/DNA methodology that allowed for screening on a single sample.3Currently, most states use a

methodology that includes DNA muta-tion panels.4

In Illinois, NBS for CF began in March 2008 and uses an IRT/DNA methodol-ogy. Blood spots with an IRT value in the highest 4% for that day (typical range: 50 –70 ng/mL) are secondarily screened using a 44-mutation panel (changed to a 36-mutation panel in April 2010 after our study was closed to recruitment). Children in whom 1 or more mutations were identified were referred for a sweat test. Children with an ultra-high IRT (⬎170 ng/mL) were also referred for a sweat test to iden-tify infants whose mutations may not be included in the state panel. In 2009, no mutation was found in 20% (132 of 644) of infants referred for a sweat test. During this same year, there were 58 confirmed CF cases, only 2 of which were children with no identified muta-tions (Michael Petros, MS, MPH, DrPH, Illinois Department of Public Health, personal communication, June 2010). We designed this study to evaluate the knowledge and attitudes of parents whose child received a positive result from the NBS but a negative result from the sweat test.


Parents of children who received a positive result from the screen for CF but who received a negative result from the diagnostic sweat test at 1 of 2

sites (University of Chicago or Chil-dren’s Memorial Hospital) were in-vited to participate. At the University of Chicago, a genetic counselor called parents whose infants received a pos-itive result from the screen and who were born at the University of Chicago to schedule the sweat test. All other parents who called to schedule an ap-pointment at either the University of Chicago or Children’s Memorial Hospi-tal contacted the respective CF center. At the time the appointment was scheduled, most parents spoke to a ge-netic counselor who explained what CF is, informed the parents about what they could expect with the sweat test, and explained the likelihood of receiv-ing a positive result from the sweat test.

Formal genetic counseling was pro-vided in conjunction with the sweat test and included information about NBS, the genetics and clinical manifes-tations of CF, the types of problems that children with CF frequently expe-rience, and what treatments are avail-able, although given the likelihood of a false-positive result, more emphasis was placed on explaining the process and meaning of the sweat test and car-rier status. All parents were informed whether a mutation had been found with their child’s NBS. If a mutation was found, they were told which muta-tion, and the meaning of carrier detec-tion for the wider family also is dis-cussed. Parents whose infants did not have a mutation identified were told that this does not mean that the child is definitely not a carrier only that the child did not have any of the common mutations. Cascade CF carrier screen-ing of the parents and then other rela-tives is then explored. Parents were given 1 of 2 handouts, depending on whether a mutation was found. That same handout also was sent to the pe-diatrician along with a letter tailored to the child’s workup within 2 weeks of

the sweat test. The pediatricians were told which mutation was found during screening. At Children’s Memorial Hos-pital, the parents received a copy of the letter sent to the pediatrician; therefore, they were given information on the specific mutation. The parents who had a sweat test at the University of Chicago did not get a copy of this letter.

The genetic counselors at both sites helped recruit parents for this study. Parents whose children had a negative result from the sweat test were asked by the genetic counselor to give permission for researchers to contact them after a brief delay. The contact information of those who agreed was sent to the re-searchers (Dr Ross and Ms Lang), who then waited at least 6 weeks before at-tempting to contact participants.

Prospective participants were called in sequential order until 90 surveys were completed. Multiple attempts were made to contact prospective par-ticipants and continued until (1) con-tact was made and the survey was completed or the prospective partici-pant refused, (2) all contact telephone numbers had become invalid or dis-connected, (3) the child reached 1 year of age, or (4) the recruitment goal was achieved. The first parent contacted was interviewed unless he/she ex-pressed a preference for the other parent to complete the survey. Partici-pants were excluded if they were aged less than 18 years, were non–English-speaking, were not the biological par-ent of the child, did not attend the sweat test, or if the child’s sweat-test result was abnormal. Parents were of-fered $10 cash for their participation. Both University of Chicago and Chil-dren’s Memorial Hospital Institutional Review Boards approved this project and allowed for oral consent and the waiver of written informed consent.

The survey consisted of questions re-garding awareness of CF, discussion of


status, knowledge of CF, and demo-graphics (survey available from Dr Ross). Anxiety to the abnormal NBS re-sult was assessed using a 4-point Lik-ert scale (1, not at all worried; 2, mini-mally worried; 3, somewhat worried; 4, very worried). The question was posed during the initial contact for all partic-ipants and after scheduling the sweat test for those who recalled speaking to a genetic counselor. After the first 12 surveys were completed, a question was added to determine parents’ cur-rent anxiety. Knowledge of CF was as-sessed by asking 20 knowledge ques-tions: 19 true-false and 1 multiple choice, with 3 options. Each partici-pant’s responses were graded as cor-rect or incorcor-rect, and the percentage correct was recorded as their “knowl-edge score.” Knowl“knowl-edge questions were previously used in a study on ma-ternal knowledge of CF.5 One

open-ended question asked parents how to improve the process.

Statistics were performed using SPSS 16.0 (SPSS, Chicago, IL). Correlations between demographic variables and knowledge were assessed by using Pearson correlations. Those demo-graphics that showed significant cor-relation were included in linear re-gression to control for colinearity. Anxiety scores were compared by us-ing ␹2 tests. For all statistical tests,

significance was set atP⬍.05. Quali-tative data were coded by 2 research-ers (Ms Lang and Dr Ross) and revised until 100% consensus was achieved.


From August 2008 to June 2010, a total of 113 parents were contacted. Two cases were excluded (1 because the infant’s parents were not the primary caretakers and 1 had 2 mutations identified and a borderline sweat test).

giving a response rate of 81% (90 of 111).

The majority of parents reported their ethnicity as non-Hispanic white (53 of 90 [59%]) or non-Hispanic African American (23 of 90 [26%]) (Table 1). The average age of parents was 30⫾6 years, and more than half (49 of 90 [55%]) were first-time parents. The majority of participants were female (78 of 90 [87%]), were married (61 of 90 [68%]), had private health insur-ance (60 of 90 [67%]), and had at least a Bachelor’s degree (50 of 90 [56%]).

The average age of the infants was 111⫾52 days, and the majority (73 of 90 [81%]) of infants received a

conclu-interview for 59% (53 of 90) of partici-pants. Sixty-three (70%) of the sweat tests took place at Children’s Memo-rial Hospital and 27 (30%) at the Uni-versity of Chicago; however, most chil-dren were born at hospitals not affiliated with the 2 sweat-test centers (58 of 90 [64%]). A mutation was found in 78 (87%) children.

A majority (58 of 90 [64%]) of parents had heard of CF before their child’s NBS, although only 16% (14 of 90) knew someone with CF. Twenty-six (29%) parents reported specifically discuss-ing CF or carrier testdiscuss-ing for CF with their prenatal care providers. One-third (30 of 90) of participants re-ported discussing NBS in general with their (or their partner’s) prenatal care provider.

Of 90 participants, 56 (62%) were noti-fied of their child’s abnormal NBS re-sults by the child’s pediatrician, 24 (27%) were notified by the child’s birth hospital, and 6 (7%) were notified by a genetic counselor. Only 21% (19 of 90) of participants learned of the abnor-mal NBS result in person; the rest were notified over the telephone or via let-ter. At the time of initial notification, most (54 of 90 [60%]) parents received information about CF and the meaning of the NBS result (60 of 90 [67%]); how-ever, only half (45 of 90 [50%]) re-ceived information about the sweat-test procedure. All but 3 parents scheduled the appointment them-selves. Seventy-three of 87 (84%) parents recalled speaking to a ge-netic counselor when, or soon after, they scheduled the sweat test. Most parents recall being provided with information regarding CF (70 of 87 [81%]), the NBS result (72 of 87 [83%]), and the sweat-test proce-dure (75 of 87 [86%]) when they scheduled the sweat test.

TABLE 1 Demographics (N⫽90)


Gender, female,n(%) 78 (87) First-time parent,n(%) 49 (55)

Married,n(%) 61 (68)

Private health insurance,n(%) 60 (67) Race/ethnicity,n(%)

African American 23 (26)

Caucasian 53 (59)

Hispanic 8 (9)

Other (4 Asian, 2 other) 6 (6) Education,n(%)

Did not graduate high school 6 (7) High school graduate 11 (12)

Some college 23 (26)

College graduate 30 (33) Some graduate school 1 (1) Graduate degree 19 (21) Sweat-test location,n(%)

University of Chicago 27 (30) Children’s Memorial Hospital

(Northwestern University)

63 (70)

Hospital in which child was born,n(%) University of Chicago 6 (7) Prentice Women’s Hospital

(Northwestern University)

26 (29)

Other 58 (64)

Mutation found,n(%), yes 78 (87) ⱕ4 wk (28 d) between the day of birth

and a conclusive sweat test,n(%) 73 (81)

ⱕ2 mo (60 d) between the sweat test and the survey,n(%)

37 (41)

Age, mean⫾SD

Age of parent, y 30⫾6 Age of parent at birth of first child

(n⫽88), y



Seventy percent (63 of 90) of parents were “very worried” when first notified of their child’s abnormal NBS result and 82% (64 of 78) were “not at all wor-ried” after receiving the results of the sweat test, although 24% (22 of 90) still think about the NBS/sweat test at least once a week. For 73 parents who re-called speaking to a genetic counselor when they scheduled the sweat test, their anxiety decreased even before the sweat test took place (see Fig 1). Seventy-three percent (53 of 73) of par-ents described themselves as being very worried at initial contact, but only 25% (18 of 73) remained so after speaking to the counselor (P⬍.001), and none were worried after receiving the results of the sweat test. At the time of the survey, 88 of 90 participants considered their child to be in good to excellent health. Both par-ents who rated their child’s health as fair

mentioned other unrelated health issues.

Parental understanding of their child’s NBS and sweat-test results were mixed. All but 1 parent correctly

under-stood that their child had a normal sweat-test result and 94% (85 of 90) correctly understood that their child does not have CF. Only 62 of 78 (79%)

participants whose child had a muta-tion knew their child was definitely a carrier for CF. Among those for whom no mutation was found (n⫽12), only 1 (8%) correctly understood that their child may be a carrier for CF. Ten par-ticipants thought their child was defi-nitely not a carrier for CF (revealing a

poor understanding of the concept of residual risk), and 1 participant re-mained concerned that his or her child may have CF.

Seventy-five participants who identi-fied their child as a carrier or possible carrier were asked about their atti-tudes toward disclosure of the child’s carrier status (Table 2). All 75 (100%) participants believed that their part-ner and the child’s future partpart-ner should know that the child is a carrier for CF, and over 90% (73 of 75 [97%]) believe the child’s primary physician and siblings (69 of 75 [92%]) should know. Most also would inform their siblings (65 of 75 [87%]) and parents (63 of 75 [84%]) that their child is a carrier. Only 57% (43 of 75) believed that other relatives should know, and 9% (7 of 75) actively did not want them to know. They were even more reluc-tant to share carrier information out-side of the family and with health care providers, with increasing percent-ages not wanting health insurance


18 8

31 11



1 2


0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

On inial noficaon (n = 73)

Aer talking with a genec counselor when scheduling the sweat test

(n = 73)

≥6 wk aer negave sweat test result and formal genec counseling

(n = 66)a



ent of



Not worried at all Minimally worried Modestly worried Very worried


Parental anxiety in those parents who recall speaking to a genetic counselor when scheduling the sweat test. Parents were asked to recall their anxiety (1) when initially told of their child’s abnormal NBS result, (2) after speaking to the genetic counselor when scheduling the sweat test, and (3)ⱖ6 weeks after the sweat test and genetic counseling.aN66 because the question was added after the first 12 interviews were completed, and 7 recalled speaking to

a genetic counselor when scheduling the sweat test.


companies (19 of 75 [25%]), the child’s teachers (28 of 75 [37%]), church lead-ers (33 of 75 [44%]), and the child’s classmates (44 of 74 [59%]) to know. All but 1 plan to tell their child he or she is a carrier for CF, with most (55 of 75 [73%]) planning to defer this dis-cussion until the child is a teenager or young adult.

By the time of the survey, the majority of the participants had told their par-ents (94%) and siblings (89%) and their partner’s parents (89%) and sib-lings (75%) that their child was a car-rier. However, only 50% had told any of their other relatives and 36% any of their partner’s other relatives. The av-erage knowledge score for parents was 78%. The majority (74 of 90, 82%) of parents looked up information about CF, and those who reported that they had researched CF did signifi-cantly better on the knowledge ques-tions that those who did not (80% vs 69%; P ⫽ .001). All but 1 (73 of 74 [99%]) of those who researched CF used the Internet. Nevertheless, there were several knowledge gaps. For ex-ample, 26% (23 of 90) of parents thought that over time, carriers of CF can develop CF and 38% (34 of 90) thought that CF can be inherited if 1 parent has CF even if the other parent is not a carrier (Table 3). The greatest

misunderstanding was that 62% (56 of 90) of parents thought that it was im-portant to know if one is a CF carrier because of possible health risks asso-ciated with being a carrier. Higher knowledge scores correlated with be-ing married, bebe-ing white, havbe-ing a

col-life. All of these variables were colin-ear on regression analysis (data not shown).

Forty participants reported having been tested for CF carrier status, most commonly during prenatal visits, both for participants (24 of 90 [27%]) and their partners (14 of 90 [17%]). An ad-ditional 13% (12 of 90) of participants and 3% (3 of 90) of partners decided to be tested after their child’s sweat test. Of 90 participants, 13 reported that both parents had been tested for their CF carrier status by the time of this survey. Of those 77 couples in which 1 or both partners had not been tested, only 47% (36 of 77) are interested in genetic testing and only 10% (8 of 77) had made an appointment by the time of the interview. Couples in which 1 or both parents have been tested are

Your partner 100 0 0

Your siblings 87 13 0

Your parentsa 84 15 2

Child’s siblings 92 8 0

Other relativesa 57 35 9

The child’s pediatrician 97 3 0

Emergency-department physician 52 47 1

Child’s dentist 28 59 13

Health insurance company 35 40 25

Child’s teachers 21 41 37

Child’s classmatesb 1 39 59

Church leader(s) 16 40 44

Child’s future partner 100 0 0

aAdds up to more than 100%: 1 participant said both “yes” for some and “do not want them to know” for others. bn74 (1 participant refused to answer).

TABLE 3 Knowledge Questions (N⫽90)

Question Correct Answer Percentage Correct

(95% Confidence Interval)

CF can be transmitted by physical contact with an affected person

False 100

CF is a genetic condition True 98 (95–100)

Individuals with CF get frequent respiratory (breathing or lung) infections

True 95 (91–100)

Individuals with CF usually have breathing problems True 94 (90–99)

There is no cure for CF True 93 (88–99)

There are things a person with CF can do to avoid some of the complications

True 92 (87–98)

Individuals with CF are usually of normal intelligence True 90 (84–96) Individuals with CF need to take special vitamins True 87 (80–94) People who are carriers of CF have a mild form of CF False 86 (78–93) Individuals with CF usually have problems with hearing False 84 (77–92) To inherit CF, both parents must have at least 1 CF gene True 83 (75–91) You can be a carrier for CF even if neither parent has CF or

is a carrier

False 78 (69–86)

Individuals with CF often fail to grow at a normal rate True 76 (66–85) Over time, people who are carriers for CF can

develop CF

False 74 (65–84)

Women with CF often have fertility problems False 64 (54–75) CF is most common in which ethnic group? (options: African,

American, Caucasian, and equally in all races)

Caucasian 64 (54–75)

CF can be inherited if 1 parent has CF, even if the other parent is not a carrier and does not have the disease

False 62 (52–72)

Playing sports will worsen the symptoms of CF False 51 (41–62) Men with CF often have fertility problems True 50 (39–61) It is important to know if you are a carrier for CF even if you

do not have any symptoms, because of possible health risks associated with being a carrier


more likely to be married, white, col-lege graduates with private health in-surance (data not shown).

Eighty-three of 90 (92%) parents are supportive or very supportive of NBS for CF, although 4 parents do not port it and 3 are only minimally sup-portive. Twelve parents spontaneously

expressed appreciation for talking with a genetic counselor both at scheduling and at the time of confir-matory testing, although 2 parents ex-pressed dissatisfaction with having to undergo genetic counseling at the time

of the sweat test. Although 18 partici-pants could think of “no changes” that they would recommend to the process, the other 72 offered multiple sugges-tions. The 3 most common themes were (1) the need for more discus-sions about NBS in general and about

CF by both prenatal and pediatric pro-viders (n⫽36); (2) notification of an abnormal NBS result should be per-formed by someone who is knowledge-able about CF screening and who is sensitive to parental anxiety (n⫽26); and (3) negative attitudes about the sweat-test experience, including

logis-tic complaints and the burdensome nature of the test (n⫽19).


Previous studies have found that a false-positive NBS results is a highly stressful event but that the majority of parents quickly recover after confir-matory test results reveal that the

child is unaffected.6,7Stress is

wors-ened by the delay between initial con-tact and diagnostic testing,8

particu-larly when the informant has limited knowledge.9,10In our study, we found

that talking to a genetic counselor at the time of scheduling the sweat test

significantly helped to reduce anxiety, even before testing was done.10 This

process change needs further valida-tion but may be useful to minimize the

harms caused by false-positive NBS results.7,11,12

Not surprisingly, we also found that anxiety further decreased after being informed of a negative sweat-test sult. However, residual concerns re-mained. Nearly one-fourth of parents still were thinking about the sweat test at least once per week 6 or more

weeks after the sweat test. We did not ask why they were thinking about the sweat test, so it is difficult to say whether their thoughts signified con-cern about their child’s health, inter-est in genetic tinter-esting, or the need for additional discussions with family


Our racial/ethnic data may seem somewhat nonrepresentative of the CF community, which is more than 90%

white, whereas one-fourth of our par-ticipants were African American. Our data, however, are representative of CF NBS results in Illinois. In 2009, 331 of 591 (56%) of all infants with a positive sweat-test result for CF were white and 133 (23%) were black (Illinois Depart-ment of Public Health, personal

com-munication, October 2010). In our sam-ple 26% of participants self-identified as African American, which is consis-tent with the fact that both our centers were located in the city of Chicago, where there are more ethnic minori-ties than in other parts of the state. Ten percent (62 of 591) of the infants who

received a positive result from their CF screen in Illinois were Hispanic, and 9% of our participants self-identified as Hispanic, although we only inter-viewed in English. Of note, the racial ethnic composition of 59 children diag-nosed in Illinois with CF after a positive sweat-test result revealed a higher proportion of white infants (n ⫽ 40 [68%]) and Hispanic infants (n ⫽10 [17%]) and a lower percentage of black infants (n⫽3 [5%]) and infants of unknown race (n⫽ 6 [10%]) than

were found in those with an abnormal screen result and normal sweat-test result (Illinois Department of Public Health, personal communication, Octo-ber 2010).

The experience of our respondents, however, is not representative of all parents whose child had a positive NBS result for CF in Illinois. In our sample, over 80% had received a negative sweat-test result by 4 weeks of age, which is consistent with the CF guide-lines.13,14In contrast, the average age

of a first sweat test at all Illinois cen-ters now exceeds 30 days of age.8All of

our respondents (100%) received ge-netic counseling at the time of the sweat test, compared with an average of 80% of parents in Illinois who re-ceived counseling after a positive NBS result.15

Although overall knowledge of CF was high, some significant gaps existed. Thirty percent of parents in our study were confused about their child’s CF carrier status, particularly in those families where no mutation was found. Confusion regarding the concept of re-sidual risk also has been found in other studies16–19of CF NBS as well as

in prenatal CF carrier testing,20–22but

our data show more confusion than these other studies despite the fact that our participants were highly educated.

Although one might predict that the de-tection and disclosure of a carrier in a family with a previously unknown his-tory of a genetic condition would lead to testing of biological relatives, our respondents did not report high up-take of carrier testing of relatives, a finding reported by other research-ers.14,23We do not know whether

rela-tives were electing carrier testing and not informing our respondents, whether they did not understand the genetic implications of a positive pro-band, or whether they truly were not interested.


both prenatal and pediatric providers, a finding seen commonly in other stud-ies.8,10,24–27This lack of discussion is the

case despite the fact that prenatal and pediatric guidelines recommend dis-cussions of NBS.26,28 Two parents

ex-pressed dissatisfaction with the man-datory genetic counseling at the time of the sweat test, which was consistent with another study that found that some parents do not believe that this is the best time for counseling.29The

ad-vantage is that it increases the likeli-hood that families will receive counsel-ing.30Additional research is needed to

understand how different families can be accommodated. Additional re-search also is needed to understand the value that parents place on learn-ing about their infant’s carrier status, whether identification of carrier sta-tus is perceived as a benefit or as a harm, whether they share this infor-mation with the child as he or she ma-tures, and whether this finding encour-ages cascade carrier status testing of parents and their first- or second-degree relatives and with whom they

There are several limitations to our study. First, we only reported on those respondents who agreed to be con-tacted after receiving the negative sweat-test results. We do not know the demographics of those who refused to be recontacted nor how they would have responded to our questions. Sec-ond, our data regarding anxiety and disclosure patterns are at a single point in time, early in the life course after a negative sweat-test result, and may not reflect changes that occur during the first year and beyond. Third, we started to ask about anxiety after the sweat-test results after 12 surveys were completed. Given the uniform low level of anxiety, the missing data should not change our results or inter-pretation. Nevertheless, our finding that there is some residual doubt re-garding the child’s health despite a negative sweat-test result is similar to the findings of other studies and should not be ignored when expanding NBS programs. Fourth, the knowledge questionnaire was nonvalidated, al-though it had been used in a previous study.5At least 1 statement, “It is

im-associated with being a carrier,” was difficult to understand because it con-flated both knowledge and value.


Parents want more information about NBS and want to be informed of abnor-mal screening results by a knowledge-able, sensitive person. Although paren-tal knowledge about CF was high in the population sampled, confusion about the child’s carrier status and the con-cept of residual risk persisted even af-ter genetic counseling. How the misun-derstanding of genetic risk influences decisions about disclosure to relatives and post–sweat test carrier testing of the parents is unknown.


This research was funded in part by the Illinois Department of Public Health.

We acknowledge Christopher Tan, MS, Lindsay Rhodes, MS, and Cathy Long, MS, for their assistance with partici-pant recruitment.


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DEFINING LIFE:It seems as if each year at least one of my four children comes home from school with a science project in which he or she has to describe or define life. Over the years, I have felt reasonably comfortable helping them with this assignment. However, some key assumptions about what life is have re-cently been challenged. We have always assumed that six elements are essen-tial to all life: phosphorous, carbon, oxygen, nitrogen, hydrogen, and sulfur. Phosphorous is part of nucleic acid and is essential in the storage and release of energy in the form of ATP. Now it turns out some bacteria don’t need phos-phorous. As reported inThe New York Times(December 2, 2010: Science) a bacterium from a California lake bottom has been grown in an arsenic rich environment and has replaced intracellular phosphorous atoms, even those in DNA, with those of arsenic. The arsenic loving bacterium are a little different in that they are larger and have more intracellular empty spaces but nonetheless, are fully functional. The implications are enormous. For example, while search-ing for life on Mars, scientists made certain assumptions and looked for evi-dence of specific molecules and reactions. That a bacterium can use arsenic, usually a toxic compound, instead of phosphorous as a fundamental building block suggests we may need to revisit what we look for on distant planets and even on our own. As the character played by Jeff Goldblum in the movieJurassic Parknotes, “life finds a way.”

Noted by WVR, MD


DOI: 10.1542/peds.2010-2284 originally published online January 10, 2011;





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DOI: 10.1542/peds.2010-2284 originally published online January 10, 2011;




Colleen Walsh Lang, Susanna A. McColley, Lucille A. Lester and Lainie Friedman

Negative Sweat-Test

Parental Understanding of Newborn Screening for Cystic Fibrosis After a

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TABLE 1 Demographics (N � 90)


Demographics (N � 90) p.3
FIGURE 1Parental anxiety in those parents who recall speaking to a genetic counselor when scheduling the sweat test

FIGURE 1Parental

anxiety in those parents who recall speaking to a genetic counselor when scheduling the sweat test p.4
TABLE 2 Disclosure of Carrier Status (N � 75)


Disclosure of Carrier Status (N � 75) p.5
TABLE 3 Knowledge Questions (N � 90)


Knowledge Questions (N � 90) p.5