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Clinical Epidemiology logoLink to Clinical Epidemiology
. 2016 Oct 19;8:415–423. doi: 10.2147/CLEP.S108906

Evaluation of algorithms for registry-based detection of acute myocardial infarction following percutaneous coronary intervention

Gro Egholm 1,2,*,, Morten Madsen 2,*, Troels Thim 1, Morten Schmidt 2,3, Evald Høj Christiansen 1, Hans Erik Bøtker 1, Michael Maeng 1
PMCID: PMC5076540  PMID: 27799822

Abstract

Background

Registry-based monitoring of the safety and efficacy of interventions in patients with ischemic heart disease requires validated algorithms.

Objective

We aimed to evaluate algorithms to identify acute myocardial infarction (AMI) in the Danish National Patient Registry following percutaneous coronary intervention (PCI).

Methods

Patients enrolled in clinical drug-eluting stent studies at the Department of Cardiology, Aarhus University Hospital, Denmark, from January 2006 to August 2012 were included. These patients were evaluated for ischemic events, including AMI, during follow-up using an end point committee adjudication of AMI as reference standard.

Results

Of 5,719 included patients, 285 patients suffered AMI within a mean follow-up time of 3 years after stent implantation. An AMI discharge diagnosis (primary or secondary) from any acute or elective admission had a sensitivity of 95%, a specificity of 93%, and a positive predictive value of 42%. Restriction to acute admissions decreased the sensitivity to 94% but increased the specificity to 98% and the positive predictive value to 73%. Further restriction to include only AMI as primary diagnosis from acute admissions decreased the sensitivity further to 82%, but increased the specificity to 99% and the positive predictive value to 81%. Restriction to patients admitted to hospitals with a coronary angiography catheterization laboratory increased the positive predictive value to 87%.

Conclusion

Algorithms utilizing additional information from the Danish National Patient Registry yield different sensitivities, specificities, and predictive values in registry-based detection of AMI following PCI. We were able to identify AMI following PCI with moderate-to-high validity. However, the choice of algorithm will depend on the specific study purpose.

Keywords: Danish National Patient Registry, registry, percutaneous coronary intervention, validity, sensitivity, specificity

Introduction

First-time ischemic events such as acute myocardial infarction (AMI) are used to study the risk and to improve the prognosis of ischemic heart disease. AMI is often treated with percutaneous coronary intervention (PCI). To monitor the safety and efficacy of this intervention, robust registry-based algorithms are required for the detection of AMI in this population.1

In Denmark, record linkage using the ten-digit civil registration number offers unique possibilities for epidemiological studies.2 As the key registry, the Danish National Patient Registry contains data on all Danish hospital admissions and outpatient clinic visits, starting in 1997.3 Thereby, the Danish National Patient Registry can be utilized for the detection of AMI in the Danish population. However, to what extent the Danish National Patient Registry can be used to identify AMI in patients with existing ischemic heart disease undergoing PCI is unknown.3 In this study, we aimed to create an algorithm for using the Danish National Patient Registry to identify patients with AMI following PCI.

Methods

Study design, setting, and participants

We performed the evaluation in a population of patients treated with drug-eluting coronary stents as a part of clinical drug-eluting coronary stent studies. These patients were enrolled in the Central Region of Denmark, which covers a population of ~1.3 million inhabitants corresponding to 23% of the Danish population. The patients were treated with PCI at the Department of Cardiology, Aarhus University Hospital, Denmark, from January 2006 to August 2012.47 Using this cohort with end-point committee adjudication of AMI as reference standard, we compared different algorithms for the detection of AMI in the Danish National Patient Registry following PCI.

Definition of AMI

Clinical end-point committee adjudication of AMI was performed in each trial as previously described.47 Briefly, possible AMI events were screened using the Danish National Patient Registry3 and the Western Denmark Heart Registry.8 Possible events were subsequently reviewed by a clinical end-point committee, with reference to the contemporary universal definitions of AMI.9 The end-point committee also reviewed all deaths in order to classify these as cardiac or noncardiac. In case of cardiac death, the end-point committee evaluated whether it was secondary to AMI.

The Danish National Patient Registry

The Danish National Patient Registry contains information on all nonpsychiatric hospital admissions since 1977 and emergency room and outpatient clinic visits since 1995.3 The registry contains data from each admission including the admission and discharge dates, admission type, discharge diagnoses, and procedures performed during the admission.3 The International Classification of Diseases tenth revision (ICD-10) codes have been used since 1994. All admissions have one primary discharge diagnosis reflecting the primary reason for the admission. Additionally, admissions may have one or more secondary discharge diagnoses reflecting coexisting conditions. Discharge diagnoses are determined exclusively by the discharging physician.

The Danish national health care service is tax supported and provides free health care. Mandatory reporting to the Danish National Patient Registry, which is managed by the Danish Health Authority, ensures nationwide coverage of AMI hospitalisations.3

Algorithms for detection of AMI in the Danish National Patient Registry

To establish an algorithm for the detection of AMI in the Danish National Patient Registry, we identified AMI from discharge diagnoses using the ICD-10 code I21. Diagnoses were identified as primary (only) and primary or secondary discharge diagnoses. Furthermore, algorithms were based on patient contact type (inpatient admission), admission type (acute or elective), and hospital type (with or without coronary angiography capability). Table 1 shows the details of the different algorithms.

Table 1.

Algorithms for detection of acute myocardial infarction following percutaneous coronary intervention in the Danish National Patient Registry

Algorithm AMI diagnosis Admission type Hospital
A Primary or secondary All inpatients All hospitals
B Primary only All inpatients All hospitals
C Primary or secondary Acute admissions only All hospitals
D Primary only Acute admissions only All hospitals
E Primary or secondary Acute admissions only Hospitals with CAG capability
F Primary only Acute admissions only Hospitals with CAG capability

Abbreviations: AMI, acute myocardial infarction; CAG, coronary angiography.

Statistical analyses

Follow-up of the trial participants started upon discharge after drug-eluting stent implantation.47 Patients were followed until a first AMI was detected in the Danish National Patient Registry, by the end-point committee, or in both simultaneously.

For each algorithm for identifying AMI following PCI in the Danish National Patient Registry, we calculated sensitivity, specificity, and predictive values using the end-point committee adjudicated cases of AMI as reference. We stratified the results according to AMI status at the time of PCI (AMI before PCI, AMI at same date of PCI, or PCI without prior AMI) to determine whether recurrent AMI could be detected equally well as first-time AMI. We also stratified according to sex, age (≤65 years vs >65 years), indication for PCI (acute coronary syndrome vs stable angina pectoris), and time from index procedure to AMI. Confidence intervals were calculated with Jeffrey’s method.10

All statistical analyses were performed using SAS software Version 9.4 (SAS Institute Inc., Cary, NC, USA). The study was approved by the Danish Data Protection Agency (Ref no 2012-41-0164) and the Danish Health Authority (Ref no 6-8011-270/2). Registry studies do not require ethical committee approval or patients consent in Denmark.

Results

We evaluated 5,719 patients with a mean follow-up time of 3 years. Of these, 285 had an end-point committee adjudicated AMI. Baseline characteristics of the PCI cohort are presented in Table 2.

Table 2.

Baseline characteristics of patients with percutaneous coronary intervention

N=5,719
Demographics and comorbidities
Age, years, median (IQR) 66 (58–73)
Male sex 4,271 (74.7)
Body mass index >30 kg/m2 1,308 (22.9)
Active smokinga 1,819 (31.8)
Treatment for hypertensiona 3,046 (53.3)
Treatment for hypercholesterolemiaa 3,625 (63.4)
Diabetesa 905 (15.8)
Charlson comorbidity index =0 2,679 (46.8)
Charlson comorbidity index =1 1,448 (25.3)
Charlson comorbidity index ≥2 1,592 (27.8)
Procedure characteristics
More than one stent 2,212 (38.7)
Stent length ≥20 mm 3,025 (52.9)
PCI indication ACS 2,650 (46.3)
PCI indication SAP 2,878 (50.3)
Calendar year of percutaneous coronary intervention
2006 718 (12.6)
2007 643 (11.2)
2008 643 (11.2)
2009 1,050 (18.4)
2010 1,005 (17.6)
2011 942 (16.5)
2012 718 (12.6)

Notes: Data presented as number (%) unless otherwise stated.

a

Missing information was <3%, missing values on smoking, diabetes and treatment were considered “not smoking”, “not having diabetes”, and “not treated”, respectively.

Abbreviations: IQR, interquartile range; PCI, percutaneous coronary intervention; ACS, acute coronary syndrome; SAP, stable angina pectoris.

The results from different algorithms are reported in Table 3 and Figure 1. Since patients with a detected AMI, either by the algorithm or by the end-point committee, were censored from the time of AMI detection, the number of patients with AMI and the average follow-up period vary between algorithm evaluations. Two-way tables for each algorithm evaluation are provided in Tables S1S6.

Table 3.

Performance of algorithms for detection of acute myocardial infarction following percutaneous coronary intervention in the Danish National Patient Registry

Algorithm Sensitivity, % (95% CI) Specificity, % (95% CI) Negative predictive value, % (95% CI) Positive predictive value, % (95% CI)
A 95.2 (92.2–97.3) 93.4 (92.7–94.0) 99.7 (99.6–99.9) 41.7 (37.9–45.7)
B 85.0 (80.5–88.8) 98.2 (97.8–98.5) 99.2 (99.0–99.4) 70.4 (65.4–75.1)
C 93.9 (90.6–96.3) 98.3 (97.9–98.6) 99.7 (99.5–99.8) 73.4 (68.6–77.8)
D 82.1 (77.3–86.3) 99.0 (98.7–99.2) 99.1 (98.8–99.3) 81.0 (76.1–85.2)
E 67.7 (62.1–73.0) 99.0 (98.7–99.2) 98.3 (98.0–98.7) 78.0 (72.5–82.8)
F 58.0 (52.1–63.6) 99.5 (99.3–99.7) 97.8 (97.4–98.2) 86.8 (81.4–91.0)

Note: A, diagnosis type: primary or secondary, all inpatients; B, diagnosis type: primary, all inpatients; C, diagnosis type: primary or secondary and acute admission; D, diagnosis type: primary and acute admission; E, diagnosis type: primary or secondary and acute admission at a hospital with coronary angiography capability; and F, diagnosis type: primary and acute admission at a hospital with coronary angiography capability.

Abbreviation: CI, confidence interval.

Figure 1.

Figure 1

Sensitivity vs 1-positive predictive value for algorithms A–F.

Notes: A, diagnosis type: primary or secondary, all inpatients; B, diagnosis type: primary, all inpatients; C, diagnosis type: primary or secondary and acute admission; D, diagnosis type: primary and acute admission; E, diagnosis type: primary or secondary and acute admission at a hospital with coronary angiography capability; and F, diagnosis type: primary and acute admission at a hospital with coronary angiography capability.

Abbreviation: PPV, positive predictive value.

The algorithms with the best performance were the combination of AMI as primary (algorithm D) or primary or secondary (C) discharge diagnosis combined with acute admission. A broader algorithm (A) combining AMI as primary or secondary discharge diagnosis and all inpatients, instead of acute admissions, improved the sensitivity (95%), but decreased the positive predictive value considerably (42%). Restricting the algorithm to admissions at a hospital with coronary angiography capability increased the positive predictive value. However, these narrower algorithms all had a decreased sensitivity (Table 3, Figure 1).

Evaluation of a broad algorithm of AMI diagnosis (code I21) as either primary or secondary diagnosis and inpatient (algorithm A, Table 3) showed that 13 patients with a validated AMI were not detected (Table S1). These AMIs resulted in cardiac arrest (n=6) and were recorded as such with the corresponding ICD-10 code in the Danish National Patient Registry. For the remaining patients, the discharge diagnosis codes covered various ICD-10 codes for ischemic heart disease, examination for angina, and examination for acute coronary syndrome.

Evaluation of a narrow algorithm of AMI diagnosis (code I21) as both primary or secondary diagnosis and acute admission (algorithm C, Table 2) showed that 95 patients were recorded with AMI diagnoses in the Danish National Patient Registry without having an end-point committee adjudicated AMI (Table S3). The majority of these were patients admitted for examination for angina or examination for acute coronary syndrome.

The stratified analyses of algorithm C are reported in Table 4, with corresponding two-way tables provided in Tables S7S23. Sex and age had no major impact on the parameters. Among patients with acute coronary syndrome, positive predictive value was lower than among patients with stable angina pectoris. Time from index procedure to AMI seemed to influence positive predictive values, which were lowest within the first 30 days after discharge following PCI and improved thereafter.

Table 4.

Performance of algorithm C (all acute admissions with acute myocardial infarction as primary or secondary discharge diagnosis) across subgroups

Sensitivity, % (95% CI) Specificity, % (95% CI) Negative predictive value, % (95% CI) Positive predictive value, % (95% CI)
Sex
Female 91.7 (83.6–96.4) 98.0 (97.2–98.7) 99.6 (99.1–99.8) 71.0 (61.2–79.4)
Male 94.7 (91.0–97.1) 98.3 (97.9–98.7) 99.7 (99.5–99.9) 74.2 (68.7–79.2)
Age
≤65 years 95.7 (90.8–98.3) 98.3 (97.7–98.7) 99.8 (99.6–99.9) 70.7 (63.3–77.4)
>65 years 92.6 (87.9–95.9) 98.2 (97.7–98.7) 99.6 (99.3–99.8) 75.5 (69.2–81.1)
Indication for stent implantation
Acute coronary syndrome 93.0 (87.9–96.3) 97.5 (96.9–98.1) 99.6 (99.3–99.8) 68.0 (61.2–74.3)
Stable angina pectoris 94.9 (90.2–97.7) 98.9 (98.4–99.2) 99.8 (99.5–99.9) 79.8 (73.1–85.4)
Prior myocardial infarction
Myocardial infarction prior to index admission 96.1 (90.9–98.7) 97.8 (96.8–98.5) 99.7 (99.2–99.9) 78.4 (70.6–84.9)
Myocardial infarction at index admission 92.4 (85.0–96.8) 97.3 (96.4–98.0) 99.6 (99.2–99.8) 62.9 (53.9–71.3)
No prior myocardial infarction 92.9 (86.5–96.7) 99.1 (98.6–99.4) 99.7 (99.5–99.9) 78.4 (70.3–85.2)
Time from stent implantation to detection of acute myocardial infarction
0–30 days 89.7 (74.9–97.0) 99.5 (99.3–99.7) 99.9 (99.9–100) 50.0 (36.7–63.3)
>30–1 year 94.2 (87.7–97.7) 99.3 (99.1–99.5) 99.9 (99.8–100) 67.5 (58.8–75.4)
<1 years 94.8 (89.6–97.8) 98.8 (98.5–99.1) 99.9 (99.8–100) 63.0 (55.6–69.9)
1–<2 years 98.1 (91.7–99.8) 99.5 (99.2–99.7) 99.9 (99.8–100) 72.6 (61.6–81.8)
2–<3 years 89.8 (80.2–95.6) 99.8 (99.6–99.9) 99.8 (99.7–99.9) 88.3 (78.5–94.6)
3–<4 years 94.1 (82.4–98.8) 99.8 (99.6–99.9) 99.9 (99.7–100) 88.9 (75.7–96.1)
4–<5 years 88.2 (67.3–97.5) 100 (99.8–100) 99.9 (99.7–100) 100 (78.2–100)
>30 days to 5 years 93.6 (90.1–96.1) 98.7 (98.4–99.0) 99.7 (99.5–99.8) 77.2 (72.3–81.7)

Abbreviation: CI, confidence interval

Discussion

We found that different algorithms yielded different sensitivities, specificities, and predictive values to detect AMI in the Danish National Patient Registry. The choice of algorithm will depend on the specific study purpose. However, combining the discharge diagnosis of AMI (I21) and acute admission yielded a better positive predictive value for patients with prior PCI than use of a discharge diagnosis of AMI alone.

Apart from the diagnosis AMI, our algorithms relied on the variable “acute admission”, which has been shown to have a high validity in the Danish National Patient Registry.11 Previously, the validity of AMI diagnoses in the general population, as registered in the Danish National Patient Registry, has been validated using medical records,12,13 discharge summaries,14,15 or a clinical registry.16 We recorded a lower positive predictive value of first-time AMI in the Danish National Patient Registry than in these earlier studies.1214 This was expected as our study population consisted of patients with established ischemic heart disease undergoing PCI. These patients are therefore more likely to be given a later discharge diagnosis of AMI, ie, to be misclassified due to their prior medical history. Similar misclassification has also been previously shown for other conditions, eg, venous thromboembolism.16 In agreement with this interpretation, we found a lower positive predictive value of the algorithm among patients with AMI during the index admission or with acute coronary syndrome as indication for stent implantation and within the first 30 days after stent implantation as compared to later.

The choice of algorithm will depend on the specific study purpose. For example, in registry-based randomized clinical trials with end-point adjudication by an end-point committee, it is important to detect as many of the potential events as possible. In this case, a broad algorithm, like algorithm A, seems the optimal choice. The low positive predictive value for this algorithm will be corrected by the end-point committee. In traditional randomized cohort studies relying on registry-based end points, ie, without adjudication by an end-point committee, algorithms C and D are preferable due to the combination of high sensitivity (although lower than algorithm A) and higher positive predictive values. Finally, in case–control studies, a high positive predictive value is preferred to correctly detect cases.

A small number of patients with adjudicated AMI did not have this diagnosis in the Danish National Patient Registry. One half of these patients died from cardiac arrest and were diagnosed with AMI by the end-point committee when the cause of death was reviewed. The other half had various ischemia-related diagnoses and were diagnosed by endpoint committee review of all angiographies and coronary interventions during the study period. A composite end point of registry-based AMI and all-cause death, often used in registry-based studies, would thus include half of the missed AMIs, ie, only very few true events would be overlooked by a use of combined end point and thereby improve sensitivity.

Strengths and limitations

We were able to evaluate the described algorithms using a large study population with end-point committee-validated AMIs. In comparison with earlier studies, this gave us an opportunity to evaluate sensitivity and specificity of the algorithms and also the positive predictive values in a subgroup of patients undergoing PCI. Thus, this study included patients treated with drug-eluting coronary stents, and the reported sensitivities and specificities of the different algorithms may not extend to the general population, to patients with ischemic heart disease without stent implantation, or to patients without previous ischemic heart disease.

Conclusion

Different algorithms utilizing additional information from the Danish National Patient Registry yielded different sensitivities, specificities, and predictive values in registry-based detection of AMI following PCI. The choice of algorithm will depend on the specific study purpose. However, it was possible to identify algorithms for AMI detection following PCI in the Danish National Patient Registry with moderate-to-high validity.

Supplementary Material

Table S1.

Two-way table for detection algorithm A

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 258 13 271
No AMI 360 5,088 5,448
Total 618 5,101 5,719

Note: I21 as either primary or secondary discharge diagnoses for an inpatient, all admission types (acute or elective), and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Register; AMI, acute myocardial infarction.

Table S2.

Two-way table for detection algorithm B

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 238 42 280
No AMI 100 5,339 5,439
Total 338 5,381 5,719

Note: I21 as primary discharge diagnoses for an inpatient, all admission types (acute or elective), and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Register; AMI, acute myocardial infarction.

Table S3.

Two-way table for detection algorithm C

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 262 17 279
No AMI 95 5,345 5,440
Total 357 5,369 5,719

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Register; AMI, acute myocardial infarction.

Table S4.

Two-way table for detection algorithm D

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 230 50 280
No AMI 54 5,385 5,439
Total 284 5,435 5,719

Note: I21 as primary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Register; AMI, acute myocardial infarction.

Table S5.

Two-way table for detection algorithm E

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 191 54 245
No AMI 91 5,384 5,475
Total 282 5,438 5,719

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital with coronary angiography capability.

Abbreviations: DNPR, Danish National Patient Register; AMI, acute myocardial infarction.

Table S6.

Two-way table for detection algorithm F

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 164 119 283
No AMI 25 5,411 5,436
Total 189 5,530 5,719

Note: I21 as primary discharge diagnoses, acute admission, and hospital with coronary angiography capability.

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S7.

Two-way table for algorithm C stratified for female sex

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 66 6 72
No AMI 27 1,349 1,376
Total 357 1,355 1,448

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S8.

Two-way table for algorithm C stratified for male sex

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 196 11 207
No AMI 68 3,996 4,064
Total 264 4,007 4,271

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S9.

Two-way table for algorithm C stratified for age ≤ 65 years

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 111 5 116
No AMI 46 2,647 2,693
Total 157 2,652 2,809

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S10.

Two-way table for algorithm C stratified for age > 65 years

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 151 12 163
No AMI 49 2,698 2,747
Total 200 2,710 2,910

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S11.

Two-way table for algorithm C stratified for indication of index stent, acute coronary syndrome

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 132 10 142
No AMI 62 2,446 2,508
Total 194 2,456 2,650

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S12.

Two-way table for algorithm C stratified for indication of index stent, stable angina

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 130 7 137
No AMI 33 2,899 2,932
Total 163 2,906 3,069

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S13.

Two-way table for algorithm C stratified on acute myocardial infarction prior to index admission

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 98 4 102
No AMI 27 1,189 1,216
Total 125 1,193 1,318

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S14.

Two-way table for algorithm C stratified on acute myocardial infarction at index admission

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 73 6 79
No AMI 43 1,541 1,584
Total 116 1,547 1,663

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S15.

Two-way table for algorithm C stratified on no prior acute myocardial infarction

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 91 7 98
No AMI 25 2,616 2,641
Total 116 2,623 2,739

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S16.

Two-way table for algorithm C stratified on time from admission, 0–30 days

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 26 3 29
No AMI 26 5,664 5,690
Total 52 5,667 5,719

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S17.

Two-way table for algorithm C stratified on time from admission, >30 days to 1 year

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 81 5 86
No AMI 39 5,527 5,566
Total 120 5,532 5,652

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S18.

Two-way table for algorithm C stratified on time from admission, < 1 year

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 109 6 115
No AMI 64 1,628 1,692
Total 173 1,634 1,807

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S19.

Two-way table for algorithm C stratified on time from admission, 1–2 years

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 53 1 54
No AMI 20 90 110
Total 73 91 164

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S20.

Two-way table for algorithm C stratified on time from admission, 2–3 years

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 53 6 59
No AMI 7 1,489 1,496
Total 60 1,495 1,555

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Register; AMI, acute myocardial infarction.

Table S21.

Two-way table for algorithm C stratified on time from admission, 3–4 years

Detected in DNPR

Detected in end point committee AMI No AMI Total
AMI 32 2 34
No AMI 4 61 65
Total 36 63 99

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Register; AMI, acute myocardial infarction.

Table S22.

Two-way table for algorithm C stratified on time from admission, 4–5 years

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 15 2 17
No AMI 0 2,077 2,077
Total 15 2,079 2,094

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Register; AMI, acute myocardial infarction.

Table S23.

Two-way table for algorithm C stratified on time from admission, >30 days to 5 years

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 234 16 250
No AMI 69 5,333 5,402
Total 303 5,349 5,652

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Register; AMI, acute myocardial infarction.

Footnotes

Disclosure

The authors report no conflicts of interest in this work.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Table S1.

Two-way table for detection algorithm A

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 258 13 271
No AMI 360 5,088 5,448
Total 618 5,101 5,719

Note: I21 as either primary or secondary discharge diagnoses for an inpatient, all admission types (acute or elective), and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Register; AMI, acute myocardial infarction.

Table S2.

Two-way table for detection algorithm B

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 238 42 280
No AMI 100 5,339 5,439
Total 338 5,381 5,719

Note: I21 as primary discharge diagnoses for an inpatient, all admission types (acute or elective), and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Register; AMI, acute myocardial infarction.

Table S3.

Two-way table for detection algorithm C

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 262 17 279
No AMI 95 5,345 5,440
Total 357 5,369 5,719

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Register; AMI, acute myocardial infarction.

Table S4.

Two-way table for detection algorithm D

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 230 50 280
No AMI 54 5,385 5,439
Total 284 5,435 5,719

Note: I21 as primary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Register; AMI, acute myocardial infarction.

Table S5.

Two-way table for detection algorithm E

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 191 54 245
No AMI 91 5,384 5,475
Total 282 5,438 5,719

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital with coronary angiography capability.

Abbreviations: DNPR, Danish National Patient Register; AMI, acute myocardial infarction.

Table S6.

Two-way table for detection algorithm F

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 164 119 283
No AMI 25 5,411 5,436
Total 189 5,530 5,719

Note: I21 as primary discharge diagnoses, acute admission, and hospital with coronary angiography capability.

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S7.

Two-way table for algorithm C stratified for female sex

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 66 6 72
No AMI 27 1,349 1,376
Total 357 1,355 1,448

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S8.

Two-way table for algorithm C stratified for male sex

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 196 11 207
No AMI 68 3,996 4,064
Total 264 4,007 4,271

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S9.

Two-way table for algorithm C stratified for age ≤ 65 years

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 111 5 116
No AMI 46 2,647 2,693
Total 157 2,652 2,809

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S10.

Two-way table for algorithm C stratified for age > 65 years

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 151 12 163
No AMI 49 2,698 2,747
Total 200 2,710 2,910

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S11.

Two-way table for algorithm C stratified for indication of index stent, acute coronary syndrome

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 132 10 142
No AMI 62 2,446 2,508
Total 194 2,456 2,650

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S12.

Two-way table for algorithm C stratified for indication of index stent, stable angina

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 130 7 137
No AMI 33 2,899 2,932
Total 163 2,906 3,069

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S13.

Two-way table for algorithm C stratified on acute myocardial infarction prior to index admission

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 98 4 102
No AMI 27 1,189 1,216
Total 125 1,193 1,318

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S14.

Two-way table for algorithm C stratified on acute myocardial infarction at index admission

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 73 6 79
No AMI 43 1,541 1,584
Total 116 1,547 1,663

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S15.

Two-way table for algorithm C stratified on no prior acute myocardial infarction

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 91 7 98
No AMI 25 2,616 2,641
Total 116 2,623 2,739

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S16.

Two-way table for algorithm C stratified on time from admission, 0–30 days

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 26 3 29
No AMI 26 5,664 5,690
Total 52 5,667 5,719

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S17.

Two-way table for algorithm C stratified on time from admission, >30 days to 1 year

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 81 5 86
No AMI 39 5,527 5,566
Total 120 5,532 5,652

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S18.

Two-way table for algorithm C stratified on time from admission, < 1 year

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 109 6 115
No AMI 64 1,628 1,692
Total 173 1,634 1,807

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S19.

Two-way table for algorithm C stratified on time from admission, 1–2 years

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 53 1 54
No AMI 20 90 110
Total 73 91 164

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Registry; AMI, acute myocardial infarction.

Table S20.

Two-way table for algorithm C stratified on time from admission, 2–3 years

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 53 6 59
No AMI 7 1,489 1,496
Total 60 1,495 1,555

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Register; AMI, acute myocardial infarction.

Table S21.

Two-way table for algorithm C stratified on time from admission, 3–4 years

Detected in DNPR

Detected in end point committee AMI No AMI Total
AMI 32 2 34
No AMI 4 61 65
Total 36 63 99

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Register; AMI, acute myocardial infarction.

Table S22.

Two-way table for algorithm C stratified on time from admission, 4–5 years

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 15 2 17
No AMI 0 2,077 2,077
Total 15 2,079 2,094

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Register; AMI, acute myocardial infarction.

Table S23.

Two-way table for algorithm C stratified on time from admission, >30 days to 5 years

Detected in DNPR

Detected in end-point committee AMI No AMI Total
AMI 234 16 250
No AMI 69 5,333 5,402
Total 303 5,349 5,652

Note: I21 as either primary or secondary discharge diagnoses, acute admission, and hospital (with or without coronary angiography capability).

Abbreviations: DNPR, Danish National Patient Register; AMI, acute myocardial infarction.


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