Table 4.

Accuracy of ICD-9-CM Codes in the Primary Diagnosis Position

Cohort	Algorithm	PPV (95% CI)	Sensitivity (95% CI)	Specificity (95% CI)	NPV (95% CI)
Any stroke cohort	AIS	88.6 (84.7-92.6)	58.6 (53.6-63.6)	99.8 (99.7-99.9)	99.0 (98.8-99.1)
	ICH	88.6 (78.9-98.3)	67.4 (54.8-79.9)	100.0 (99.9-100.0)	99.9 (99.8-99.9)
	AIS/ICH	90.5 (87.1-94.0)	60.4 (55.8-65.1)	99.8 (99.6-99.9)	98.9 (98.7-99.0)
First stroke cohort	AIS	91.1 (86.6-95.5)	58.6 (52.4-64.7)	99.9 (99.8-100)	99.2 (99.1-99.4)
	ICH	84.8 (71.8-97.9)	59.9 (44.9-74.9)	100.0 (99.9-100.0)	99.9 (99.8-99.9)
	AIS/ICH	92.6 (88.8-96.4)	59.5 (53.8-65.1)	99.9 (99.8-100)	99.1 (98.9-99.3)

Abbreviations: AIS, acute ischemic stroke; ICD-9-CM, International Classification of Diseases, Ninth Revision, Clinical Modification; ICH, intracranial hemorrhage; NPV, negative predictive value; PPV, positive predictive value.