Table 4.

Criteria for the modified idiopathic pulmonary fibrosis algorithm

Criteria	Notes
Inclusion criteria
Age ≥50 yr	At time of first claim for either ICD-9 code 516.3 or ICD-9-CM code 516.31
At least two IPF diagnostic claims	At least two claims for either ICD-9 code 516.3 or ICD-9-CM code 516.31 at least 1 mo apart
Chest CT procedure claim*	Any chest CT procedure code prior to the first diagnostic claim for IPF
Exclusion criteria
Any diagnostic claim for an alternative ILD diagnosis†	Any claims for alternative ILD codes occurring on or after the first claim for IPF

Definition of abbreviations: CT = computed tomography; ICD-9 = International Classification of Diseases, Ninth Revision; ICD-9-CM = International Classification of Diseases, Ninth Revision, Clinical Modification; ILD = interstitial lung disease; IPF = idiopathic pulmonary fibrosis.

^*Chest CT procedure codes: ICD-9-CM 87.41 and Current Procedural Terminology, 4th Edition, codes 71250, 71260, and 71270.

^†Exclusionary ICD-9 codes for alternative ILD diagnoses: 135, 237.7, 272.7, 277.3, 277.8, 446.21, 446.4, 495, 500–505, 506.4, 508.1, 508.8, 516.0, 516.1, 516.32–516.37, 516.2, 516.8, 516.9, 517.0, 517.2, 517.8, 518.3, 555, 710.0, 710.0–710.4, 714.0, 714.81, 720, and 759.5.