Validation of ICD-9-CM and ICD-10-CM Diagnostic Codes for Identifying Patients with Out-of-Hospital Cardiac Arrest in a National Health Insurance Claims Database

Figures & data

Table 1 Case Definition Algorithms for Out-of-Hospital Cardiac Arrest

Algorithm	CA Codes	VA Codes	Primary Diagnosis Field	First Three Diagnosis Fields	Any Diagnosis Field	AND Billing Code for Triage Acuity Level 1	AND Billing Code for CPR
A	X		X
B	X	X	X
C	X			X
D	X	X		X
E	X				X
F	X	X			X
G	X		X			X
H	X	X	X			X
I	X			X		X
J	X	X		X		X
K	X				X	X
L	X	X			X	X
M	X		X				X
N	X	X	X				X
O	X			X			X
P	X	X		X			X
Q	X				X		X
R	X	X			X		X

Abbreviations: CA, cardiac arrest; CPR, cardiopulmonary resuscitation; VA, ventricular arrhythmia.

Figure 1 Flow chart outlining the true out-of-hospital cardiac arrest verification process.

Abbreviations: ED, emergency department; ICD, International Classification of Diseases diagnostic codes; OHCA, out-of-hospital cardiac arrest.

Table 2 Performance of the Best Two Algorithms for All Patients (n = 985,526)

		Ascertained OHCA		Sensitivity (%) (95% CI)	Specificity (%) (95% CI)	PPV (%) (95% CI)	NPV (%) (95% CI)	Kappa (95% CI)
		Positive	Negative
Alg C	Positive	2174	225	89.5 (88.2–90.7)	100.0 (100.0–100.0)	90.6 (89.4–91.8)	100.0 (100.0–100.0)	0.900 (0.891–0.909)
	Negative	255	982,872
Alg K	Positive	2079	143	85.6 (84.1–87.0)	100.0 (100.0–100.0)	93.6 (92.5–94.5)	100.0 (100.0–100.0)	0.894 (0.884–0.903)
	Negative	350	982,954

Abbreviations: Alg, algorithm; CI, confidence interval; PPV, positive predictive value; NPV, negative predictive value.

Table 3 Reasons for False-Negative and False-Positive Identification of OHCA by Algorithms C and K

Reason	n
False negatives for algorithm C	255
Coded for underlying diseases instead of CA	121
Miscoded as unspecified illness or symptoms (R69, R68.89 or 799.89)	59
CA codes listed in the 4th or 5th diagnosis fields	49
VA codes listed in the 4th and 5th diagnosis fields	11
VA codes listed in the first three diagnosis fields	15
False positives for algorithm C	225
IHCA occurring during the hospitalization	130
IHCA occurring at the emergency department	72
Miscoded as CA or VA	23
False negatives for algorithm K	350
Coded for underlying diseases instead of CA	144
Without a billing code for triage acuity level 1	144
Miscoding as unspecified illness or symptoms codes (R69, R68.89 or 799.89)	52
VA codes listed in the 4th and 5th diagnosis fields	10
False positives for algorithm K	143
IHCA occurring during the hospitalization	81
IHCA occurring at the emergency department	61
Miscoded as CA or VA	1

Abbreviations: CA, cardiac arrest; IHCA, in-hospital cardiac arrest; OHCA, out-of-hospital cardiac arrest; VA, ventricular arrhythmia.

Table 4 Performance of the Best Algorithms Among Different Subgroups Stratified by ICD Coding System, Age, and Type of Claims

Subgroup	Alg	Sensitivity (%) (95% CI)	Specificity (%) (95% CI)	PPV (%) (95% CI)	NPV (%) (95% CI)	Kappa (95% CI)
ICD-9-CM (2010–2015) (n = 561,331)	C	90.8 (89.2–92.3)	100.0 (100.0–100.0)	92.3 (90.7–93.6)	100.0 (100.0–100.0)	0.915 (0.904–0.926)
ICD-10-CM (2016–2020) (n = 424,195)	K	88.4 (86.3–90.2)	100.0 (100.0–100.0)	91.2 (89.3–92.9)	100.0 (100.0–100.0)	0.898 (0.884–0.911)
Adult patients (≥18 y/o) (n = 731,993)	C	89.6 (88.3–90.8)	100.0 (100.0–100.0)	91.0 (89.7–92.1)	100.0 (100.0–100.0)	0.903 (0.894–0.912)
Pediatric patients (<18 y/o) (n = 253,533)	I	74.5 (61.0–85.3)	100.0 (100.0–100.0)	100.0 (91.4–100.0)	100.0 (100.0–100.0)	0.854 (0.779–0.930)
Outpatient claims (n = 803,018)	C	90.8 (89.4–92.1)	100.0 (100.0–100.0)	96.4 (95.4–97.2)	100.0 (100.0–100.0)	0.935 (0.927–0.943)
Inpatient claims (n = 182,508)	K	89.1 (86.1–91.6)	99.9 (99.9–100.0)	80.9 (77.5–84.0)	100.0 (100.0–100.0)	0.848 (0.825–0.870)

Abbreviations: Alg, algorithm; CI, confidence interval; ICD-9-CM, International Classification of Diseases, Ninth Revision, Clinical Modification; ICD-10-CM, International Classification of Diseases, Tenth Revision, Clinical Modification; PPV, positive predictive value; NPV, negative predictive value.

Figure 2 The sensitivity and positive predictive value of algorithms C (A) and K (B) to identify OHCA from 2010 to 2020.

Abbreviations: ICD, International Classification of Diseases diagnostic codes; PPV, positive predictive value.