Positive predictive value of ICD-9 codes 410 and 411 in the identification of cases of acute coronary syndromes in the Saskatchewan Hospital automated database.
BACKGROUND
Case definitions are essential to epidemiological research.


OBJECTIVE
To evaluate ICD-9 codes 410 and 411 to identify cases of acute coronary syndromes (ACS), and the clinical information availability in the administrative and hospital discharge records of Saskatchewan, Canada.


METHODS
In the context of a safety cohort study, we identified hospitalisations with primary discharge codes 410 (2260) and 411 (799). We selected all records with code 411, and a random sample (200) with code 410. Based on information obtained by trained abstractors from hospital records, events were classified by two cardiologists as definite or possible according to adapted AHA/ESC criteria. The validity of 410 and 411 codes was assessed by calculating the positive predictive value (PPV). Completeness of the recorded information on risk factors and use of aspirin was explored.


RESULTS
The PPVs of the codes 410 and 411 for ACS were 0.96 (95%CI: 0. 92-0.98) and 0.86 (95%CI: 0.83-0.88), respectively. The PPV of 410 for acute myocardial infarction (AMI) was 0.95 (95%CI: 0.91-0.98). The PPV of 411 was 0.73 (95%CI: 0.70-0.77) for primary unstable angina (UA) and 0.09 (95%CI: 0.07-0.11) for AMI. Hospital charts review revealed key information for clinical variables, smoking, obesity and use of aspirin at admission.


CONCLUSIONS
ICD-9 410 code has high PPV for AMI cases, likewise 411 for UA cases. Case validation remains important in epidemiological studies with administrative health databases. Given the pathophysiology of ACS, both AMI and UA might be used as study end points. In addition to code 410, we recommend the use of 411 plus validation.
Varas-Lorenzo
Cristina
C
RTI-Health Solutions, Epidemiology, Barcelona, Spain. cvaras@rti.org
Castellsague
Jordi
J
Stang
Mary Rose
MR
Tomas
Luis
L
Aguado
Jaume
J
Perez-Gutthann
Susana
S
D054058:Acute Coronary Syndrome / Q000139:chemically induced* / Q000453:epidemiology*; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D000789:Angina, Unstable / Q000145:classification*; D001241:Aspirin / Q000008:administration & dosage / Q000627:therapeutic use; D015331:Cohort Studies; D016208:Databases, Factual; D005260:Female; D006761:Hospitals; D006801:Humans; D038801:International Classification of Diseases; D008297:Male; D008499:Medical Records; D008875:Middle Aged; D009203:Myocardial Infarction / Q000145:classification*; D009765:Obesity; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage / Q000627:therapeutic use; D011237:Predictive Value of Tests; D012307:Risk Factors; D012525:Saskatchewan; D012907:Smoking
D010975:Platelet Aggregation Inhibitors; D001241:Aspirin