Cystic fibrosis newborn screening: the importance of bloodspot sample quality

Current Status of Newborn Bloodspot Screening Worldwide 2024: A Comprehensive Review of Recent Activities (2020-2023)

Newborn bloodspot screening (NBS) began in the early 1960s based on the work of Dr. Robert "Bob" Guthrie in Buffalo, NY, USA. His development of a screening test for phenylketonuria on blood absorbed onto a special filter paper and transported to a remote testing laboratory began it all. Expansion of NBS to large numbers of asymptomatic congenital conditions flourishes in many settings while it has not yet been realized in others. The need for NBS as an efficient and effective public health prevention strategy that contributes to lowered morbidity and mortality wherever it is sustained is well known in the medical field but not necessarily by political policy makers. Acknowledging the value of national NBS reports published in 2007, the authors collaborated to create a worldwide NBS update in 2015. In a continuing attempt to review the progress of NBS globally, and to move towards a more harmonized and equitable screening system, we have updated our 2015 report with information available at the beginning of 2024. Reports on sub-Saharan Africa and the Caribbean, missing in 2015, have been included. Tables popular in the previous report have been updated with an eye towards harmonized comparisons. To emphasize areas needing attention globally, we have used regional tables containing similar listings of conditions screened, numbers of screening laboratories, and time at which specimen collection is recommended. Discussions are limited to bloodspot screening.

Severe lung disease in children with cystic fibrosis missed in newborn screening

BACKGROUND

Cystic fibrosis (CF) is now routinely diagnosed through newborn screening (NBS), but the tests employed in the USA have been evolving for two decades as missed cases become recognized and lab methods improve in association with more knowledge about CF genetics. New Jersey was among the first states to implement CF NBS in 2001 when it introduced the original two-tiered method that combined measurements of immunoreactive trypsinogen (IRT) with detection of the principal pathogenic variant (F508del) in the cystic fibrosis transmembrane conductance regulator (CFTR) gene.

OBJECTIVE

With continuation of the IRT/DNA (F508del) algorithm for two decades and identification of screening false negative children, we decided to examine the condition of some missed cases with special attention to their respiratory status.

METHODS

To strengthen the arguments for quality improvement in New Jersey's CF NBS program, we reviewed and evaluated false negative cases to determine the potential extent of preventable patient suffering as a consequence of delayed diagnoses.

RESULTS

Five children with CF who had false negative screening results were studied in detail. In each case there was a different cause of the negative screening results. They all had clinically significant/severe lung disease, ranging from chronic cough with CF pathogens on respiratory culture at a young age to respiratory failure.

CONCLUSION

This case series highlights the consequences of false negative screening results, which served as the impetus to upgrade New Jersey's CF NBS algorithm. Implemented changes include lowering the IRT cutoff to 70 ng/mL and expanding to a 139 variant CFTR panel. In 2023, a floating IRT cutoff is anticipated to be implemented.

Cystic Fibrosis Cases Missed by Newborn Bloodspot Screening-Towards a Consistent Definition and Data Acquisition

Repeated European surveys of newborn bloodspot screening (NBS) have shown varied strategies for collecting missed cases, and information on data collection differs among countries/regions, hampering data comparison. The ECFS Neonatal Screening Working Group defined missed cases by NBS as either false negatives, protocol-related, concerning analytical issues, or non-protocol-related, concerning pre- and post-analytical issues. A questionnaire has been designed and sent to all key workers identified in each NBS programme to assess the feasibility of collecting data on missed cases, the stage of the NBS programme when the system failed, and individual patient data on each missed case.

Why cystic fibrosis newborn screening programs have failed to meet original expectations… thus far

This Commentary summarizes what the author has learned in 46 years of research on newborn screening (NBS) for cystic fibrosis (CF) combined with healthcare and public health practice. The original expectation was that screening for this relatively common, life-threatening genetic disorder would lead to consistently timely diagnoses in the neonatal period and be equitable. Unfortunately, this ambitious goal has not been achieved in the USA despite the availability of an excellent, although imperfect, 2-tiered screening test employing immunoreactive trypsinogen (IRT) and DNA analysis for pathogenic variants in the gene that encodes the cystic fibrosis transmembrane conductance regulator (CFTR). In fact, variations in the quality of NBS programs, inconsistencies in their operations, and disparities in outcomes have been prominent features. The causes include leadership challenges and deficiencies among both CF centers and NBS labs; failures to form effective partnerships among CF centers and with NBS programs; relatively rapid implementation after 2005 with variable quality planning; misunderstandings and erroneous dogma about CF; data limitations regarding IRT, especially cutoff values, and CFTR genetics; tolerance of suboptimal protocols and false negative results; problems in dried blood spot collections plus a lack of transparency and national oversight; partial lack of readiness, qualifications, funding and/or willingness to innovate with floating IRT cutoffs and DNA/CFTR analyses; follow up challenges/deficiencies impairing timeliness, including sweat testing limitations; and published guidelines that are more descriptive than sufficiently critical and directive. But the lessons learned through uniquely intensive CF NBS research have been enlightening and guided the U.S. Cystic Fibrosis Foundation to nationwide quality improvement initiatives.

A computer vision approach to the assessment of dried blood spot size and quality in newborn screening

BACKGROUND

Dried blood spot (DBS) size and quality affect newborn screening (NBS) test results. Visual assessment of DBS quality is subjective.

METHODS

We developed and validated a computer vision (CV) algorithm to measure DBS diameter and identify incorrectly applied blood in images from the Panthera DBS puncher. We used CV to assess historical trends in DBS quality and correlate DBS diameter to NBS analyte concentrations in 130,620 specimens.

RESULTS

CV estimates of DBS diameter were precise (percentage coefficient of variation <1.3%) and demonstrated excellent agreement with digital calipers with a mean (standard deviation) difference of 0.23mm (0.18mm). An optimised logistic regression model showed a sensitivity of 94.3% and specificity of 96.8% for detecting incorrectly applied blood. In a validation set of images (n=40), CV agreed with an expert panel in all acceptable specimens and identified all specimens rejected by the expert panel due to incorrect blood application or DBS diameter >14mm. CV identified a reduction in unsuitable NBS specimens from 25.5% in 2015 to 2% in 2021. Each mm decrease in DBS diameter decreased analyte concentrations by up to 4.3%.

CONCLUSIONS

CV can aid assessment of DBS size and quality to harmonize specimen rejection both within and between laboratories.

Five-year performance analysis of a cystic fibrosis newborn screening program in northeastern Brazil

OBJECTIVE

To analyze the performance of the cystic fibrosis (CF) newborn screening (NBS) program over its first five years in a Brazilian northeastern state.

METHOD

A population-based study using a screening algorithm based on immunoreactive trypsinogen (IRT)/IRT. Data were retrieved from the state referral screening center registry. The program performance was evaluated using descriptive indicators such as the results of an active search, coverage, newborn's age at the time of blood sampling, the time between sample collection and its arrival at the laboratory, and the child's age at diagnosis of disease.

RESULTS

The public CF screening program covered 82.6% of the 1,017,576 births that occurred, with an accumulated five-year incidence of 1:20,767 live births. The median (25th-75th) age at diagnosis was 3.5 (2.3-7.3) months. The sampling before 7 days of life for the first IRT (IRT1) increased between 2013 and 2017 from 42.2 to 48.3%. Around 5% of IRT1 samples and 30% of the second samples were collected after 30 days of life. In the first and second stages of screening, 23.6% and 19.9% of the infants, respectively, were lost to follow-up. In both stages of screening, the samples were retained at the health units for a median (25th-75th) of 9.0 (7.0-13.0) days.

CONCLUSIONS

The coverage by the CF-NBS program was satisfactory as compared to other Brazilian state rates and the percentage of IRT1 samples collected within the first week of life increased progressively. However, time of samples retention at the health units, inappropriate sampling, inherent methodological problems, and loss of follow-up need to improve.

Missed Cystic Fibrosis Newborn Screening Cases due to Immunoreactive Trypsinogen Levels below Program Cutoffs: A National Survey of Risk Factors

Testing immunoreactive trypsinogen (IRT) is the first step in cystic fibrosis (CF) newborn screening. While high IRT is associated with CF, some cases are missed. This survey aimed to find factors associated with missed CF cases due to IRT levels below program cutoffs. Twenty-nine states responded to a U.S-wide survey and 13 supplied program-related data for low IRT false screen negative cases (CFFN) and CF true screen positive cases (CFTP) for analysis. Rates of missed CF cases and odds ratios were derived for each factor in CFFNs, and two CFFN subgroups, IRT above ("high") and below ("low") the CFFN median (39 ng/mL) compared to CFTPs for this entire sample set. Factors associated with "high" CFFN subgroup were Black race, higher IRT cutoff, fixed IRT cutoff, genotypes without two known CF-causing variants, and meconium ileus. Factors associated with "low" CFFN subgroup were older age at specimen collection, Saturday birth, hotter season of newborn dried blood spot collection, maximum ≥ 3 days laboratories could be closed, preterm birth, and formula feeding newborns. Lowering IRT cutoffs may reduce "high" IRT CFFNs. Addressing hospital and laboratory factors (like training staff in collection of blood spots, using insulated containers during transport and reducing consecutive days screening laboratories are closed) may reduce "low" IRT CFFNs.

Cystic fibrosis newborn screening: Five-year experience from a tertiary care center

BACKGROUND

Newborn screening (NBS) for cystic fibrosis (CF) was implemented in our country on January 1, 2015, based on immunoreactive trypsinogen tests (IRT/IRT). Here, we aimed to evaluate the diagnoses of patients and follow-up process within the first 5 years of NBS from a tertiary care center.

METHODS

This retrospective cohort study was conducted on patients who were admitted to our pediatric pulmonology department for sweat test (ST) via NBS. Patients with CF with negative NBS results and those with CF with positive NBS and joined our follow-up were also investigated. Clinical outcome measures were compared between patients with CF with positive and negative NBS.

RESULTS

Six hundred sixty infants who were referred for ST via NBS were included. Across the entire study population (n = 683), 11.4% of patients had CF (14.1% of had negative NBS in this CF group). The sensitivity of NBS was found as 84.9% and the positive predictive value (PPV) was 9.4%. The median age at diagnosis was older (p < 0.001), reluctance for feeding and Pseudobartter syndrome (PBS) were significantly higher at presentation in the negative NBS group. There was no statistically significant difference between the groups regarding weight-for-age (p = 0.899) and height-for-age (p = 0.491) in the first 2 years' follow-ups.

CONCLUSIONS

Our findings showed the low sensitivity and PPV of NBS; therefore, further studies based on all patients in our country are necessary for new cut-off values. PBS and reluctance for feeding should be alarm symptoms for CF even if the infants had negative NBS. Additionally, later diagnosis of patients who had negative NBS did not affect the nutritional outcomes; we need large-scale prospective studies to optimize nutritional benefits for all infants diagnosed via NBS.

Clinical findings of patients with cystic fibrosis according to newborn screening results

BACKGROUND

Cystic fibrosis (CF) is a lethal recessive genetic disease caused by loss of function associated with mutations in the CF trans-membrane conductance regulator. It is highly prevalent (approximately 1 in 3,500) in Caucasians. The aim of this study was to compare demographic and clinical features, diagnostic tests, treatments, and complications of patients with CF whose newborn screening (NBS) with twice-repeated immune reactive trypsinogen testing was positive, normal, and not performed.

METHODS

In this study, 359 of all 1,488 CF patients recorded in the CF Registry of Turkey in 2018, who had been born through the process of NBS, were evaluated. Demographic and clinical features were compared in patients diagnosed with positive NBS (Group 1), normal (Group 2), or without NBS (Group 3).

RESULTS

In Group 1, there were 299 patients, in Group 2, there were 40 patients, and in Group 3, there were 20 patients. Among all patients, the median age at diagnosis was 0.17 years. The median age at diagnosis was higher in Groups 2 and 3 than in Group 1 (P = 0.001). Fecal elastase results were higher in Group 2 (P = 0.033). The weight z-score was lower and chronic Staphylococcus aureus infection was more common in Group 3 (P = 0.017, P = 0.004, respectively).

CONCLUSIONS

Frequency of growth retardation and chronic S. aureus infection can be reduced with an early diagnosis using NBS. In the presence of clinical suspicion in patients with normal NBS, further analyses such as genetic testing should be performed, especially to prevent missing patients with severe mutations.

Improving outcomes for Colorado's IRT-IRT-DNA cystic fibrosis newborn screening algorithm by implementing floating cutoffs

The Colorado Newborn Screening Program (CO-NBS) screens for cystic fibrosis (CF) by measuring immunoreactive trypsinogen (IRT) from two screens coupled with DNA analysis (IRT/IRT/DNA). The Colorado CF Care Center identified 8 missed CF cases among 358,187 infants screened by the CO-NSP since 2016. Retrospective analysis of CO-NSP IRT data shows that a 96th percentile floating IRT cutoff with a 50 ng/mL fixed cutoff on the first screen, and second screen 50 ng/mL fixed cutoff would have identified 7 of the 8 missed cases. These efforts demonstrate the importance of continuous quality improvement in order to increase sensitivity and reduce missed cases.