The accuracy of myocardial infarction diagnosis in medical insurance claims. Korean Research Group for Cardiovascular Disease Prevention and Control

Five-Year Risk of Acute Myocardial Infarction After Acute Ischemic Stroke in Korea

Background

The long‐term incidence of acute myocardial infarction (AMI) in patients with acute ischemic stroke (AIS) has not been well defined in large cohort studies of various race‐ethnic groups.

Methods and Results

A prospective cohort of patients with AIS who were registered in a multicenter nationwide stroke registry (CRCS‐K [Clinical Research Collaboration for Stroke in Korea] registry) was followed up for the occurrence of AMI through a linkage with the National Health Insurance Service claims database. The 5‐year cumulative incidence and annual risk were estimated according to predefined demographic subgroups, stroke subtypes, a history of coronary heart disease (CHD), and known risk factors of CHD. A total of 11 720 patients with AIS were studied. The 5‐year cumulative incidence of AMI was 2.0%. The annual risk was highest in the first year after the index event (1.1%), followed by a much lower annual risk in the second to fifth years (between 0.16% and 0.27%). Among subgroups, annual risk in the first year was highest in those with a history of CHD (4.1%) compared with those without a history of CHD (0.8%). The small‐vessel occlusion subtype had a much lower incidence (0.8%) compared with large‐vessel occlusion (2.2%) or cardioembolism (2.4%) subtypes. In the multivariable analysis, history of CHD (hazard ratio, 2.84; 95% CI, 2.01–3.93) was the strongest independent predictor of AMI after AIS.

Conclusions

The incidence of AMI after AIS in South Korea was relatively low and unexpectedly highest during the first year after stroke. CHD was the most substantial risk factor for AMI after stroke and conferred an approximate 5‐fold greater risk.

Case definitions for acute myocardial infarction in administrative databases and their impact on in-hospital mortality rates

OBJECTIVE

To identify validated ICD-9-CM/ICD-10 coded case definitions for acute myocardial infarction (AMI).

DATA SOURCES

Ovid Medline (1950-2010) was searched to identify studies that validated acute myocardial infarction (AMI) case definitions. Hospital discharge abstract data and chart data were linked to validate identified AMI definitions.

STUDY DESIGN

Systematic literature review, chart review, and administrative data analysis.

DATA COLLECTION/EXTRACTION METHODS

Data on sensitivity/specificity/positive and negative predictive values (PPV and NPV) were extracted from previous studies to identify validated case definitions for AMI. These case definitions were validated in administrative data through chart review and applied to hospital discharge data to assess in-hospital mortality.

PRINCIPAL FINDINGS

Of the eight ICD-9-CM definitions validated in the literature, use of ICD-9-CM code 410 to define AMI had the highest sensitivity (94 percent) and specificity (99 percent). In our data, ICD-9-CM/ICD-10 codes 410/I21-I22 in all available coding fields had high sensitivity (83.3 percent/82.8 percent) and PPV (82.8 percent/82.2 percent). The in-hospital mortality among AMI patients identified using this case definition was 7.6 percent in ICD-9-CM data and 6.6 percent in ICD-10 data.

CONCLUSIONS

We recommend that ICD-9-CM 410 or ICD-10 I21-I22 in the primary diagnosis coding field should be used to define AMI. The use of a consistent validated case definition would improve comparability across studies.

Risks for cardiovascular disease, stroke, ischaemic heart disease, and diabetes mellitus associated with the metabolic syndrome using the new harmonised definition: findings from nationally representative longitudinal data from an Asian population

OBJECTIVE

We examined the risk of cardiovascular disease, stroke, ischaemic heart disease, and diabetes with the metabolic syndrome according to the new harmonised definition and its components using a national longitudinal data set from an Asian population.

METHODS

Data of 9791 men and women aged 20+ from 1998 and 2001 Korea National Health and Nutrition Examination Surveys were individually linked to national hospitalisation and mortality data using unique personal identification numbers. During a 5.8-year follow-up through 2005, 288 incident cardiovascular events (184 strokes and 122 cases of ischaemic heart disease) and 85 new diabetes cases have been detected.

RESULTS

Men and women with the metabolic syndrome had 48%, 39%, 64%, and 127% greater risks of cardiovascular disease, stroke, ischaemic heart disease, and diabetes, respectively, than those without the metabolic syndrome. The increased risks of cardiovascular disease, ischaemic heart disease, and diabetes remained significant after adjusting for health behaviours, bio-clinical factors, family history, and socio-demographic factors. Analysis results on population attributable risks showed that about a quarter of total diabetes occurrence and more than 10% of cardiovascular disease was attributable to the metabolic syndrome. The number of metabolic syndrome components was linearly associated with risks of outcomes. High blood pressure was significantly associated with all four outcomes while hypertriglyceridemia and hyperglycemia were also important for ischaemic heart disease and diabetes, respectively.

CONCLUSIONS

Reduction of metabolic risk factors is necessary in South Korea to lower the burden of associated diseases, especially ever-increasing ischaemic heart disease and diabetes.

Declining accuracy in disease classification on health insurance claims: should we reconsider classification by principal diagnosis?

Background

An ideal classification should have maximum intercategory variance and minimal intracategory variance. Health insurance claims typically include multiple diagnoses and are classified into different disease categories by choosing principal diagnoses. The accuracy of classification based on principal diagnoses was evaluated by comparing intercategory and intracategory variance of per-claim costs and the trend in accuracy was reviewed.

Methods

Means and standard deviations of log-transformed per-claim costs were estimated from outpatient claims data from the National Health Insurance Medical Benefit Surveys of 1995 to 2007, a period during which only the ICD10 classification was applied. Intercategory and intracategory variances were calculated for each of 38 mutually exclusive disease categories and the percentage of intercategory variance to overall variance was calculated to assess the trend in accuracy of classification.

Results

A declining trend in the percentage of intercategory variance was observed: from 19.5% in 1995 to 10% in 2007. This suggests that there was a decline in the accuracy of disease classification in discriminating per-claim costs for different disease categories. The declining trend temporarily reversed in 2002, when hospitals and clinics were directed to assign the principal diagnosis. However, this reversal was only temporary and the declining trend appears to be consistent.

Conclusions

Classification of health insurance claims based on principal diagnoses is becoming progressively less accurate in discriminating per-claim costs. Researchers who estimate disease-specific health care costs using health insurance claims must therefore proceed with caution.

Fasting blood glucose and the risk of stroke and myocardial infarction

BACKGROUND

Although diabetes is a well-known risk factor of atherosclerotic cardiovascular diseases, the cardiovascular disease risk of glycemia below the current diabetic threshold remains uncertain.

METHODS AND RESULTS

A total of 652,901 Korean men aged 30 to 64 years from the Korean National Health Insurance System were categorized into 8 groups by fasting blood glucose (FBG) level at baseline and were followed up for cardiovascular diseases occurrence during 1992-2001. Over the follow-up period of 8.8 years, 10,954 stroke and 3766 myocardial infarction events occurred. In age-adjusted analyses, there was evidence of linear associations between FBG and myocardial infarction, ischemic stroke, and intracerebral hemorrhagic stroke. However, with additional adjustment for socioeconomic position, behaviors, and other cardiovascular disease risk factors, the associations with myocardial infarction and intracerebral hemorrhagic stroke were markedly attenuated with increased risk only at the highest FBG levels (> or =7.5 mmol/L). With full adjustment, the association with ischemic stroke persisted; a linear increase in the risk of ischemic stroke was observed from FBG level of 5.6 mmol/L. When the analyses were repeated with those persons who had been diagnosed with diabetes removed, there was no evidence of associations of FBG with intracerebral hemorrhagic stroke, but the association with ischemic stroke persisted.

CONCLUSIONS

In this Korean male population, the association with high FBG differed between ischemic stroke, intracerebral hemorrhagic stroke, and myocardial infarction. The linear increase in the risk of ischemic stroke, independently of other cardiovascular risk factors, was observed at a level below the current FBG criteria for impaired fasting glucose (> or =5.6 mmol/L). However, for other cardiovascular diseases, the current cutoff for diagnosing diabetes appropriately identified Korean men at risk.

Medicaid expenditures for children with autistic spectrum disorders: 1994 to 1999

This study used data from 1994 to 1999 from one large county in Pennsylvania to estimate the Medicaid expenditures of children diagnosed with autism spectrum disorders (ASD) and to compare these expenditures with those of other Medicaid-eligible children. On average, children diagnosed with ASD had expenditures 10 times those of other children. Differences in expenditures were driven in large part by inpatient psychiatric care. Further research is required to determine whether hospitalized children could be served in less restrictive and less expensive settings. Lack of differences in ambulatory care expenditures suggests that children with ASD are not receiving additional primary care services that would be indicative of appropriately coordinated services as suggested by the medical home model.

Socioeconomic status and cardiovascular disease among men: the Korean national health service prospective cohort study

OBJECTIVES

We examined the association between socioeconomic status (SES) and myocardial infarction and stroke subtypes, including the possible mediating influence of cardiovascular risk factors.

METHODS

We evaluated data on 578756 Korean male public servants aged 30 to 58 years from August 1, 1990, to July 31, 2001.

RESULTS

SES had inverse associations with mortality because of myocardial infarction and stroke subtypes, which were not changed by an adjustment for, or stratification by, cardiovascular risk factors. For nonfatal events, SES had positive, null, and inverse associations with myocardial infarction, ischemic stroke, and hemorrhagic stroke, respectively. The association between SES and nonfatal myocardial infarction depended on the presence of risk factors and was positive only among men who had cardiovascular risk factors. Case-fatality after hospital admission for cardiovascular diagnoses was significantly lower among higher SES groups, even after risk factor adjustment.

CONCLUSIONS

Inverse SES associations with cardiovascular diseases were not mediated by cardiovascular risk factors among men who were undergoing economic transition. Socioeconomically patterned access to medical care may partly explain these socioeconomic gradients.

Socioeconomic status and cardiovascular disease among men: the Korean national health service prospective cohort study

OBJECTIVES

We examined the association between socioeconomic status (SES) and myocardial infarction and stroke subtypes, including the possible mediating influence of cardiovascular risk factors.

METHODS

We evaluated data on 578756 Korean male public servants aged 30 to 58 years from August 1, 1990, to July 31, 2001.

RESULTS

SES had inverse associations with mortality because of myocardial infarction and stroke subtypes, which were not changed by an adjustment for, or stratification by, cardiovascular risk factors. For nonfatal events, SES had positive, null, and inverse associations with myocardial infarction, ischemic stroke, and hemorrhagic stroke, respectively. The association between SES and nonfatal myocardial infarction depended on the presence of risk factors and was positive only among men who had cardiovascular risk factors. Case-fatality after hospital admission for cardiovascular diagnoses was significantly lower among higher SES groups, even after risk factor adjustment.

CONCLUSIONS

Inverse SES associations with cardiovascular diseases were not mediated by cardiovascular risk factors among men who were undergoing economic transition. Socioeconomically patterned access to medical care may partly explain these socioeconomic gradients.