Concept: Ischemic Heart Disease (IHD) / Coronary Heart Disease (CHD) - Measuring Prevalence

Definition of Coronary Heart Disease

Coronary heart disease (CHD), also called coronary artery disease (CAD), ischemic heart disease (IHD), or atherosclerotic heart disease, is the end result of the accumulation of atheromatous plaques within the walls of the arteries that supply the myocardium (the muscle of the heart). While the symptoms and signs of coronary heart disease are noted in the advanced state of disease, most individuals with coronary heart disease show no evidence of disease for decades as the disease progresses before the first onset of symptoms, often a "sudden" heart attack, finally arise. After decades of progression, some of these atheromatous plaques may rupture and (along with the activation of the blood clotting system) start limiting blood flow to the heart muscle. The disease is the most common cause of sudden death. See MedlinePlus® - Health Topics - Coronary Artery Disease for more information.

Literature Review

Table 1 summarizes five studies, published prior to 2006, that used administrative data to identify CHD cases. The literature review excluded studies that focused narrowly on only one form of CHD, such as acute myocardial infarction (AMI) or angina. None of the studies used prescription drug data to identify CHD cases from administrative data.

Manitoba Heart Disease Algorithms

The following studies describe ischemic heart disease (IHD) / coronary heart disease (CHD) algorithms developed at the Manitoba Centre for Health Policy (MCHP).

DATA SOURCES:

In the following algorithms:


• hospitalization / hospital separation information is found in the Hospital Abstracts data;
  
• physician visit / physician claims information is found in the Medical Services (Physician Claims) data; and
  
• medication / prescription drug information is found in the Drug Program Information Network (DPIN) data.

1. Fransoo et al. (2005)

In the Sex Differences in Health Status, Health Care Use, and Quality of Care: A Population-Based Analysis for Manitoba's Regional Health Authorities deliverable, Fransoo et al. defined IHD as any resident aged 19+ with one or more of the following conditions:


• one or more hospitalizations with one of ICD-9-CM diagnosis codes 410, 411, 412, 413 or 414 in any diagnosis field over two years of data, OR,
  
• two or more physician claims with one of diagnosis codes 410, 411, 412, 413 or 414 over two years of data, OR,
  
• one or more physician claim with one of diagnosis codes 410, 411, 412, 413 or 414 AND 2+ prescriptions for IHD drugs over two years of data. IHD drugs included in this study are:
  
  • Cardiac therapy (ATC Code C01)
    
  • Beta-blocking agents (ATC Code C07)
    
  • Calcium channel blockers (ATC Code C08)
    
  • Agents acting on the rennin-angiotensin system(ATC Code C09), AND
    
  • Serum lipid reducing agents (ATC Code C10)

2. Lix et al. (2006)

In the Defining and Validating Chronic Diseases: An Administrative Data Approach deliverable, Lix et al. (2006) , used ICD-9-CM codes 410 to 414 in all algorithms to identify heart disease cases. The second-level Anatomical Therapeutic Chemical (ATC) drug codes that were selected for the research, based on the results of a literature review and consultations with clinical experts were C01 (cardiac therapy), C07 (beta-blocking agents), C08 (calcium channel blockers), and C09 (agents acting on the renin-angiotensin system). All of the Drug Identification Numbers (DINs) associated with these ATC codes in the MCHP Master Formulary were included in the analysis.

The algorithms investigated in Lix et al. (2006) are based on one, two, three, or five years of data. Two algorithms in each set are based only on the physician data, two are based on either hospital or physician data, and a single algorithm used all three data sources. None of the algorithms relied exclusively on prescription drug data for identifying disease cases; prescription drug records had to appear in combination with one medical services/physician claim for an individual to be identified as a CHD case. This is because several of the drugs selected for this research are not used exclusively in the treatment or management of CHD. An algorithm that relied only on the prescription drug data was expected to have low specificity.

Table 2 reports the estimates of sensitivity, specificity, kappa, Youden's index, PPV (positive predictive value) and NPV (negative predictive value) for each of the investigated coronary heart disease algorithms. The validation was conducted using self-report data on heart disease from cycle 1.1 of the Canadian Community Health Survey (CCHS). In total, there were 371 respondents who reported having heart disease. Individuals who indicated that they had congestive heart failure (CHF) were excluded from the CCHS validation data ( N = 19), because preliminary analyses revealed that estimates of sensitivity were improved when these individuals were excluded from the data. Lix et al.(2006) did not include the ICD-9-CM code for CHF in the algorithms (i.e., ICD-9-CM 428). CCHS respondents who indicated that they had been diagnosed with heart disease were also asked to indicate whether they had angina or had previously had a heart attack.

Calculating Population-based Prevalence Rates

The population registry was used by Lix et al. (2006) to define population cohorts to derive numerator and denominator data for calculating crude provincial prevalence estimates for each algorithm from 1998/99 to 2002/03. Note: The Lix et al. (2006) estimates are based on the population 19 years of age and older.

3. Lix et al. (2008)

In the Defining and Validating Chronic Disease: An Administrative Data Approach. An Update with ICD-10-CA. deliverable, Lix et al. (2008) provided an update to the 2006 study identifying IHD with ICD-10-CA codes. The purpose of the 2008 report is to examine the validity of administrative data for monitoring the prevalence of chronic disease in Manitoba. Specific objectives are:

• Report relevant ICD-10-CA codes for ascertaining cases of chronic disease in administrative health data;
  
• Evaluate the validity of multiple algorithms for identifying disease cases from Manitoba administrative data.

The 2008 report uses the same methods and algorithms as described in the 2006 report, with the following modifications:


• ICD-10-CA codes were used to define specific chronic diseases from hospital separation data, beginning April 1, 2004. This is due to a change in coding systems used in Manitoba hospitals. The same ICD-9-CM codes identified in the 2006 report were used to identify hospital cases prior to April 1, 2004.
  
• data from the Canadian Community Health Survey (CCHS), cycle 3.1, collected from January 2005 to January 2006 were used to evaluate the validity of the administrative data. The cohort consisted of 5,099 adults 19+ years of age.
  
• eight additional algorithms were investigated: 1 or more hospital separation(s) or 1 or more physician claim(s) or 1 or more prescription record(s) over one, two, three and five years of data, AND 1 or more hospital separation(s) or 1 or more physician claim(s) or 2 or more prescription record(s) over one, two, three and five years of data.

The following ICD-10-CA codes were used to define CHD in administrative hospital separation data from April 1, 2004 to March 31, 2006:


• I20 - I25 - ischemic heart diseases

Table 3 contains the estimates of agreement kappa(κ), sensitivity, specificity, Youden's Index, PPV (positive predictive value) and NPV (negative predictive value) for each of the 28 algorithms that were investigated for CHD.

Discussion of the validation results for CHD can be found in the full report: Chapter 5: Coronary Heart Disease

Calculating Population-based Prevalence Rates

Crude provincial prevalence estimates for the 28 CHD algorithms are reported in Table 4 .

Discussion of the prevalence rates for CHD can be found in the full report: Chapter 5: Coronary Heart Disease

4. Fransoo et al. (2009), Martens et al. (2010), Chartier et al. (2012), Fransoo et al. (2013), Martens et al. (2015) and Fransoo et. al. (2019)

In the following deliverables:


• Manitoba RHA Indicators Atlas 2009 by Fransoo et al. (2009);
  
• Profile of Metis Health Status and Healthcare Utilization in Manitoba by Martens et al. (2010);
  
• Health and Healthcare Utilization of Francophones in Manitoba by Chartier et al. (2012); and
  
• The 2013 RHA Indicators Atlas by Fransoo et al. (2013)
  
• The Cost of Smoking: A Manitoba Study by Martens et al. (2015) - (see ++NOTES below)
  
• The 2019 RHA Indicators Atlas by Fransoo et al. (2019)
  
  ... Ischemic Heart Disease (IHD) is defined as: residents aged 19 years and older were diagnosed with IHD within a five year period, if they met one of the following conditions:

  ++NOTE: In Martens et al. (2015), this was restricted to survey respondents aged 12 and older in the five years prior to their survey date

• one or more hospitalizations with a diagnosis for IHD: ICD-9-CM codes 410-414, OR ICD-10-CA codes I20-I22, I24, I25; OR
  
• two or more physician visits with a diagnosis for IHD: ICD-9-CM codes 410-414; OR
  
• one physician visit with a diagnosis of IHD: ICD-9-CM codes 410-414, and two or more prescriptions for medications to treat IHD (see individual project medication lists below)

List of drugs / medications used to treat IHD (with ATC codes) - from individual MCHP reports:


• Manitoba RHA Indicators Atlas 2009 (2009)
  
• Profile of Metis Health Status and Healthcare Utilization in Manitoba (2010)
  
• Health and Healthcare Utilization of Francophones in Manitoba (2012)
  
• The 2013 RHA Indicators Atlas (2013)
  
• The 2019 RHA Indicators Atlas - Online Supplement (2019)
  
• The Cost of Smoking: A Manitoba Study (2015)
  
  ++NOTE:

  In The Cost of Smoking deliverable, for participants of the Manitoba Heart Health Survey (MHHS), there is no prescription data available. The Drug Program Information Network (DPIN) data is only available from 1995 onwards. Therefore, in this research, the definition of IHD used for MHHS participants is:
  
  

  • one or more hospitalization, or
    
  • two or more physician visits in the five years before the survey date.

  
  In addition to calculating IHD prevalence from administrative data, they investigated self-reported IHD from the survey data. In the MHHS respondents were asked, "Have you ever had a heart attack?" Possible responses include "yes", "no" or "not sure". They were then also asked, "Do you suffer from any other kind of heart disease?" Possible responses include "yes" or "no". In the National Population Health Survey (NPHS) and the Canadian Community Health Survey (CCHS) respondents were asked, "Do you have heart disease?" Possible responses include "yes", "no" or "don't know".
  
  The weighted crude self-reported prevalence of IHD was calculated for survey respondents aged 12 and older as the percentage of respondents who answered "yes" out of all respondents who gave a valid answer. Respondents who answered "don't know" or "not sure" or those with missing or invalid data were excluded from the prevalence calculation.

Further Information

For more information on IHD prevalence please see:

• section 4.7 Ischemic Heart Disease (IHD) Prevalence from The 2013 RHA Indicators Atlas;
  
• section 4.7 Ischemic Heart Disease (IHD) Prevalence from The 2019 RHA Indicators Atlas;


For more information on the prevalence rates of IHD from survey (self-reported) and administrative data from The Cost of Smoking: A Manitoba Study deliverable, see Table 4.8 Chronic Diseases of Estimated-Population-Based Sample* at Time of Survey by Smoking Status Categories in Martens et al. (2015)

5. Finlayson et al. (2010)

In the The Additional Cost of Chronic Disease in Manitoba deliverable, Finlayson et al. (2010) define CHD as one or more hospitalizations OR one or more physician visits over a five-year time period for those aged 19+ where the events are coded with an ICD code representing CHD (ICD-9-CM codes: 410-414).

6. Martens et al. (2010)

In the Health Inequities deliverable, Martens et al. (2010) define Ischemic Heart Disease (IHD) as residents aged 19 and older with one of the following conditions within a three year period:


• one or more hospitalizations with a diagnosis of IHD: ICD-9-CM codes 410-414; ICD-10-CA codes I20-I22, I24, I25; or
  
• two or more physician visits with a diagnosis of IHD: ICD-9-CM codes 410-414

NOTE: In the Health Inequities deliverable (Martens et. al, 2010), the definitions for identifying different diagnoses / conditions did not include prescriptions from the Drug Program Information Network (DPIN) data. The reason for this is to maintain consistency in the definition across time, because the earliest analysis time frame (1984) pre-dated the availability of the DPIN data (1995). For an illustration of the difference of the crude rate for cumulative mental illness with and without DPIN data over time, please see the Cumulative Mental Illness glossary term.

7. Fransoo et al. (2011)

In the Adult Obesity in Manitoba: Prevalence, Associations, and Outcomes (Fransoo et al., 2011) Deliverable, Ischemic Heart Disease (IHD) is defined as any resident aged 18 or older that met one of the following conditions:

• one or more hospitalizations within 5 years with a diagnosis for IHD: ICD-9-CM codes 410-414, OR ICD-10-CA codes I20-I22, I24, I25; OR
  
• two or more physician visits within 5 years with a diagnosis for IHD: ICD-9-CM codes 410-414; OR
  
• one physician visit with a diagnosis of IHD: ICD-9-CM codes 410-414, and two or more prescriptions for medications to treat IHD (see list of IHD medications from Adult Obesity in Manitoba: Prevalence, Associations, and Outcomes Deliverable).

NOTE:

In the Obesity deliverable, for participants of the Manitoba Heart Health Survey (MHHS) who were surveyed in 1989-1990, there is no prescription data available. The DPIN data is only available from 1995 onwards. Therefore, in this study, the definition of IHD for MHHS participants is:



• one or more hospitalizations within 5 years with a diagnosis for IHD: ICD-9-CM codes 410-414, OR ICD-10-CA codes I20-I22, I24, I25; OR
  
• two or more physician visits within 5 years with a diagnosis for IHD: ICD-9-CM codes 410-414.

8. Katz et al. (2013)

In Katz et al. (2013), they investigated the patterns of ambulatory care services (see Ambulatory Visits - Physician) delivered by primary care and specialist physicians to Manitobans with one of six chronic conditions. This study focused on Manitobans aged 19 and older over a three-year period (plus one-year follow-up) and measured how these patterns of care impact on the quality of care received. As one of the six chronic conditions investigated, ischemic heart disease (IHD) was defined as:


• at least one hospital diagnosis: IHD (ICD-10-CA codes: I20-I25) in three years OR
  
• at least two ambulatory visit diagnoses: IHD (ICD-9-CM codes: 410-414) in three years OR
  
• at least one ambulatory visit diagnosis: IHD (ICD-9-CM codes: 410-414) in three years AND at least two prescriptions: vasodilators (ATC codes: C01DA02, C01DA05, C01DA08, C01DA14), other cardiac drugs (ATC codes: C01EB09), beta blocking agents (ATC codes: C07AA02, C07AA03, C07AA05, C07AA06, C07AA12, C07AB02, C07AB03, C07AB04, C07AB07, C07AG01, C07BA05, C07BA06, C07BA12, C07CA03, C07CB03), calcium channel blockers (ATC codes: C08CA01, C08CA02, C08CA04, C08CA05, C08CA06, C08DA01, C08DB01), angiotensin converting enzyme inhibitors (ACEI; ATC codes: C09AA01, C09AA02, C09AA03, C09AA04, C09AA05, C09AA06, C09AA07, C09AA08, C09AA09, C09AA10, C09BA02, C09BA03, C09BA04, C09BA06, C09BA08), angiotensin II antagonists (ATC codes: C09CA01, C09CA02, C09CA03, C09CA04, C09CA06, C09CA07, C09DA01, C09DA02, C09DA03, C09DA04, C09DA06, C09DA07) in three years.

9. Chartier et al. (2015)

In the Care of Manitobans Living with Chronic Kidney Disease deliverable by Chartier et al. (2015) they investigated the prevalence and relative risk of IHD as a comorbidity to chronic kidney disease (CKD) and end stage kidney disease (ESKD). IHD was defined as Manitoba residents receiving one of the following diagnoses or prescriptions in the five-year fiscal period 2007/08-2011/12, using the following algorithm:


• Age Groups:
  
  • Adults: 18 years and older
  
  
• Codes and Conditions:
  
  
  • one or more inpatient hospitalizations for ischemic heart disease (ICD-9-CM: 410-414, ICD-10-CA: I20-I22, I24, I25); or
    
  • two or more physician claims for ischemic heart disease (prefix=7, ICD-9-CM: 410-414); or
    
  • one or more prescriptions for platelet aggregation inhibitors, organic nitrates, ubidecarenone, reserpine and diuretics, beta blocking agents, calcium channel blockers, agents acting on the reninangiotensin system, HMG CoA reductase inhibitors, fibrates, ezetimibe with the following ATC codes: B01AC04, B01AC22, B01AC24, C01DA02, C01DA05, C01DA08, C01DA14, C01EB09, C02LA01, C07AA02, C07AA03, C07AA05, C07AA06, C07AA12, C07AB02, C07AB03, C07AB04, C07AB07, C07AG01, C07BA05, C07BA06, C07BA12, C07CA03, C07CB03, C08CA01, C08CA02, C08CA04, C08CA05, C08CA06, C08DA01, C08DB01, C09AA01, C09AA02, C09AA03, C09AA04, C09AA05, C09AA06, C09AA07, C09AA08, C09AA09, C09AA10, C09BA02, C09BA03, C09BA04, C09BA06, C09BA08, C09CA01, C09CA02, C09CA03, C09CA04, C09CA06, C09CA07, C09CA08, C09DA01, C09DA02, C09DA03, C09DA04, C09DA06, C09DA07, C09DA08, C09DB02, C10AA01, C10AA02, C10AA03, C10AA04, C10AA05, C10AA06, C10AA07, C10AA08, C10AB04, C10AB05, C10AB02, C10AX09, C10BX03; or
    
  • one or more prescriptions for low-dose aspirin (= 325 mg; DINs: N02BA01, N02BA51, N02BA71

For more information on prevalence and relative risk, see:

• Table 4.1 Physical Health of Adults in End Stage Kidney Disease; and
  
• Table 4.5 Physical Health of Adults in Chronic Kidney Disease.

Cautions

NOTE: Lists of drugs to treat diseases change all the time: new drugs are added, drugs are taken off the market, etc. Also it is very research specific. The medication lists presented in this concept represent a starting point to identifying the medications used to treat Coronary Heart Disease. It is always preferable to consult a clinician or pharmacist.