Table 2.
Raw and positive predictive value–corrected incidence and prevalence using two case-finding algorithms from 2001 to 2014 in the Kaiser Permanente Northern California member population
| Overall Estimates | Annual Incidence* (per 100,000 Person-Years) | 95% CI | Average Prevalence* (per 100,000 Persons) | 95% CI |
|---|---|---|---|---|
| IPF algorithm† | 6.8 | 6.6–7.1 | 14.5 | 14.1–14.9 |
| PPV-corrected IPF algorithm‡ | 3.1 | 2.4–3.8 | 6.6 | 5.2–8.0 |
| IIP algorithm§ | 47.0 | 46.2–47.7 | 87.9 | 86.9–88.9 |
| PPV-corrected IIP algorithm‖ | 5.6 | 2.6–10.3 | 10.5 | 4.9–19.2 |
| IPF algorithm*, subgroups | Annual Incidence* (per 100,000 Person-Years) | 95% CI | Incidence Rate Ratio | 95% CI |
|---|---|---|---|---|
| Age, yr | ||||
| <55 | 0.7 | 0.6–0.9 | Reference | Reference |
| 55–59 | 5.1 | 4.3–6.1 | 7.1 | 3.7–13.7 |
| 60–64 | 8.8 | 7.7–10.1 | 12.6 | 6.7–23.7 |
| 65–69 | 16.1 | 14.4–18.0 | 22.2 | 11.9–41.4 |
| 70–74 | 26.4 | 23.8–29.2 | 36.0 | 19.4–66.8 |
| 75–79 | 37.2 | 33.7–41.0 | 50.6 | 27.3–93.8 |
| >80 | 50.5 | 46.9–54.4 | 70.7 | 38.3–130.7 |
| Sex | ||||
| Female | 5.8 | 5.4–6.1 | Reference | Reference |
| Male | 8.1 | 7.6–8.5 | 1.39 | 1.04–1.84 |
| Race | ||||
| White | 9.7 | 9.2–10.2 | Reference | Reference |
| Black | 5.8 | 4.8–6.8 | 0.60 | 0.45–0.79 |
| Asian | 3.5 | 3.0–4.1 | 0.36 | 0.26–0.50 |
| Hispanic | 6.6 | 5.9–7.4 | 0.70 | 0.54–0.91 |
| Other | 2.7 | 2.3–3.1 | 0.28 | 0.20–0.40 |
Definition of abbreviations: CI = confidence interval; ICD-9 = International Classification of Diseases, Ninth Revision; ICD-9-CM = International Classification of Diseases, Ninth Revision, Clinical Modification; IIP = idiopathic interstitial pneumonia; IPF = idiopathic pulmonary fibrosis; PPV = positive predictive value.
Annual incidence was calculated as the number of new cases meeting criteria for the algorithm in each calendar year divided by the total midyear adult member population of each year (i.e., person-years). Annual cumulative prevalence was calculated as the total number of current, living members meeting criteria for the algorithm in the current or any previous calendar year divided by the total midyear adult member population.
The IPF algorithm requires being older than 18 years of age, having at least one diagnostic claim for ICD-9 code 516.3 or ICD-9-CM code 516.31, and exclusion of alternative interstitial lung disease diagnostic claims.
Overall PPV from the two combined IPF algorithm validation sets (n = 141) using the adjudication diagnosis to define positive cases (PPV, 45.4%; 95% CI, 37.0–54.0).
The IIP algorithm requires being older than 50 years of age; having at least one diagnostic claim for ICD-9 code 516.3, ICD-9-CM code 516.31, or ICD-9 code 515; and exclusion of alternative interstitial lung disease diagnostic claims.
PPV from the IIP validation set (n = 75) using the adjudication diagnosis to define cases (PPV, 12.0%; 95% CI, 5.6–21.6).