Validation of an algorithm to identify incident interstitial lung disease in patients with rheumatoid arthritis

Table 4 Positive predictive value of final algorithm for incident ILD according to varying case qualification definitions

		ILD according to adjudicated gold standard
	Case qualifying ILD definition^b	Incident	Prevalent	Any ILD (incident + prevalent)	PPV for incident ILD, conditional on confirmed case of ILD	Not ILD	Total (any ILD + not ILD)	PPV for incident ILD, all cases
Final incident ILD algorithm^a	Yes, HospitalPrimary	6	1	7	86% (42%, 100%)	1	8	75% (35%, 97%)
	Yes, HospitalNonPrimary	8	1	9	89% (52%, 100%)	11	20	40% (19%, 64%)
	Yes, OutpatientCT	28	0	28	100% (88%, 100%)	5	33	85% (68%, 95%)
	Yes, OutpatientHospital	3	0	3	100% (29%, 100%)	1	4	75% (19%, 99%)
	Yes, All definitions	45	2	47	96% (85%, 100%)	18	65	69% (57%, 80%)
	Total without HospitalNonPrimary ILD Cases	37	1	38	97% (86%, 100%)	7	45	82% (68%, 92%)

ILD interstitial lung disease
^aThe algorithm excluded cases with ICD-9-CM 135 (Sarcoidosis), ICD-10-CM D869 (Sarcoidosis), and ILD Definition Codes (exhaustive list in section 5.1) through minimum of (Index Date +365 days, Outcome Date −183 days)
^bHospitalPrimary = inpatient primary diagnosis; HospitalNonPrimary = inpatient non-primary diagnosis; OutpatientCT = outpatient diagnosis preceded by CT; and OutpatientHospital = outpatient diagnosis preceded by hospitalization

ISSN: 1478-6362