It All Depends What You Count—The Importance of Definitions in Evaluation of CF Screening Performance

Abstract

Screening metrics are essential to both quality assessment and improvement, but are highly dependent on the way positive tests and cases are counted. In cystic fibrosis (CF) screening, key factors include how mild cases of late-presenting CF and CF screen positive, inconclusive diagnosis (CFSPID) are counted, whether those at prior increased risk of CF are excluded from the screened population, and which aspects of the screening pathway are considered. This paper draws on the New Zealand experience of almost forty years of newborn screening for CF. We demonstrate how different definitions impact the calculation of screening sensitivity. We suggest that, to enable meaningful comparison, CF screening reports should clarify what steps in the screening pathway are included in the assessment, as well as the algorithm used and screening target.

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

“…NBS reporting protocols are expected to result in clear and concise information exchange. A recent report in NZ emphasized that, to enable meaningful comparisons, CF screening reports should include the screening algorithm and target along with clarification of the steps in the screening pathway included in the assessment, the screening algorithm, and screening target [ 608 ]. To encourage faster recall returns for follow-up testing overall, a structured protocol for follow-up of inadequate and borderline positive NBS (including text messages to specimen submitters) was recently introduced [ 609 ].…”

Is Our Newborn Screening Working Well? A Literature Review of Quality Requirements for Newborn Blood Spot Screening (NBS) Infrastructure and Procedures

“…Ideally, these centres of expertise should be selected and supervised by medical specialty societies in accordance with objectively defined quality criteria [ 140 , 142 ]. At the programme level, clear case definitions and guidelines for confirmation diagnostics are required for all target diseases [ 1 , 31 , 32 , 33 , 81 , 94 , 143 , 144 , 145 , 146 ].…”

“…Standardised algorithms for confirmatory diagnostics, as well as case definitions for all target diseases, are crucial for the consistent reporting of NBS programmes, monitoring outcomes in newborns with confirmed diagnoses, and evaluating the NBS benefit [ 32 , 33 , 81 , 94 , 143 , 144 , 145 ]. Good epidemiological practices include defining all variables of interest precisely and operationalising them in a standardised way [ 162 ].…”

European survey of newborn bloodspot screening for CF: opportunity to address challenges and improve performance

“…To accurately compare different screening approaches, outcome data need to be collected consistently and accurately. It has been shown that different definitions of parameters significantly impact the calculation of global screening metrics such as specificity, PPV and sensitivity [21] . Metrics are dependent on the way tests and cases are counted unless definitions are clearly harmonized and they are the cornerstone for both quality assessment and improvement of programmes.…”