Table 1.
Validity of ICD-9 codes for prevalent health conditions.
| Condition | Validated events |
12-month window for ICD-9 codes | 24-month window for ICD-9 codes | ||||||
|---|---|---|---|---|---|---|---|---|---|
| PPV (95% CI) |
NPV (95% CI) |
Sensitivity (95% CI) |
Specificity (95% CI) |
PPV (95% CI) |
NPV (95% CI) |
Sensitivity (95% CI) |
Specificity (95% CI) |
||
| Previous MI | 40 | 97% (82–100%) | 87% (79–92%) | 38% (19–60%) | 100% (98–100%) | 98% (85–100%) | 88% (80–93%) | 44% (25–66%) | 100% (98–100%) |
| Angina | 26 | 83% (36–98%) | 96% (90–98%) | 57% (29–81%) | 99% (91–100%) | 85% (44–98%) | 97% (93–99%) | 74% (46–90%) | 99% (92–100%) |
| Coronary heart disease | 88 | 85% (70–93%) | 89% (78–95%) | 84% (69–92%) | 90% (78–96%) | 85% (71–93%) | 93% (82–97%) | 90% (77–96%) | 89% (78–95%) |
| Congestive heart failure | 32 | 72% (47–86%) | 99% (91–100%) | 90% (57–98%) | 95% (88–98%) | 69% (46–86%) | 98% (91–100%) | 90% (57–98%) | 94% (88–98%) |
| Previous stroke | 26 | 81% (45–95%) | 93% (85–97%) | 52% (26–76%) | 98% (92–100%) | 77% (45–93%) | 93% (85–97%) | 52% (27–76%) | 98% (93–99%) |
| Current smoking (ICD-9 codes only) | 45 | 74% (52–88%) | 84% (73–91%) | 62% (43–78%) | 90% (80–96%) | 69% (51–83%) | 89% (79–95%) | 77% (59–89%) | 85% (74–92%) |
| Current smoking (ICD-9 codes + medication use) | 45 | 77% (57–90%) | 88% (78–94%) | 73% (54–86%) | 90% (80–96%) | 71% (54–84%) | 93% (83–97%) | 77% (59–89%) | 85% (74–92%) |
International Classification of Disease, Ninth Revision (ICD-9) codes from inpatient and outpatient encounters were used to identify prevalent health conditions. Specific ICD-9 codes and validation criteria are listed in Supplemental Table 1. CI = confidence interval, MI = myocardial infarction, NPV = negative predictive value, PPV = positive predictive value.