Table 1.

Study variables by inclusion and exclusion criteria, number of states and response categories used in main analyses.

Variable	Inclusion	Exclusion 1	Number of States	Response Categories
Demographic Factors
Sex	All states 2	Subjects with sex missing or unknown	Summed for 13 states	% female, male
Race	States providing data for all study groups 2	2 States not collecting data; Subjects with race missing or unknown	Summed for 11 states	% White, Black, Other
Ethnicity	States providing data for all study groups 2	2 States not collecting data; subjects with ethnicity missing or unknown	Summed for 11 states	% Hispanic
Timing and Program Factors
Median newborn age at specimen collection and IRT testing	States providing data; subjects had data for both variables	2 States not providing one or both data items for all study groups; 2 States with zero CFFNs	9 states stratified by 1- and 2-specimen programs	Average median age weighted by state birth counts and number of CFTPs and CFFNs
Day of week birth occurred	States providing data for all study groups	2 States with missing data for CFFNs or CFTPs	Summed for 11 states	% born on different days of the week
Season of Specimen Collection	States providing data on month of specimen collection for all study groups	2 States with missing data for CFFNs or CFTPs	Summed for 11 states	% specimens collected in different seasons of the year
Maximum consecutive days lab closed 3	All states	none	Summed for 13 states	% in states with a lab that can be closed for a maximum of 3 or more or less than 3 days
Program type 3	All states	none	Summed for 13 states	% in states screening 1- or 2- specimens
CF Algorithm Factors
Median IRT value	States providing data for all study groups	3 States with missing data for CFTPs and LBs	10 states stratified by 1- and 2-specimen programs	Average median IRT weighted by the number of LBs, CFTPs and CFFNs
IRT cutoff type 3	All states	none	Summed for 13 states	% in states using a fixed or floating IRT cutoff
IRT cutoff level 3	All states	none	Summed for 13 states	% in states with an IRT cutoff of <0.96, ≥0.96, ≥0.97, ≥0.98, ≥0.99 percentiles
Biologic and Health Factors
CFTR genotype 4	States providing data for both CFTP and CFFN study groups	2 States not collecting data; subjects not undergoing genotype testing	Summed for 11 states	% in ranked categories based on CFTR2 5: 1. Both variants unidentified 2. Both variants known CF-causing 3. All other genotype combinations
Birth weight	All states 2	Subjects with birth weight missing or unknown	Summed for 13 states	% <2500, ≥2500 g
Gestational duration	States providing data for all study groups 2	5 States not collecting data; 2 States with a high proportion of missing data; subjects with gestational age missing or unknown	Summed for 6 states	% <37, ≥37 completed weeks
Infant feeding	States providing data for all study groups	7 states not collecting data; subjects with feeding data unknown or missing	Summed for 6 states	% breast only, any formula use
Meconium ileus	States providing data for both CFTP and CFFN study groups	4 States not collecting data	Summed for 9 states	% meconium ileus present, not indicated

Abbreviations: CFFN, false screen negative CF cases due to IRT below program cutoffs; CFTP, true screen positive CF infants; IRT, immunoreactive trypsinogen; LB, all screened newborns. ¹ Two CFFNs with age at blood collection > 6 months excluded in all analyses. ² For 1 state, data for all screened newborns were obtained from live births posted by CDC, Natality online databases reporting counts of live births occurring within the United States to U.S. residents (https://wonder.cdc.gov/natality.html, accessed on 20 July 2020). ³ State-level variable. ⁴ Genotype information obtained by states includes variants detected by the state testing laboratory and those reported to the program after NBS. ⁵ CFTR2, Clinical and Functional Translation of CFTR (Cystic Fibrosis Transmembrane Conductance Regulator gene), Version 11 March 2019. (https://cftr2.org/, accessed on 30 December 2019).