Elsevier

American Heart Journal

Volume 168, Issue 2, August 2014, Pages 197-204.e4
American Heart Journal

Clinical Investigation
Acute Ischemic Heart Disease
Agreement between public register and adjudication committee outcome in a cardiovascular randomized clinical trial

https://doi.org/10.1016/j.ahj.2013.12.032Get rights and content

Background

The objective of this study is to describe the agreement between randomized trial outcome assessment by committee and outcomes entirely identified through public registers.

Methods

In the CLARICOR trial, 4,372 patients with stable coronary heart disease received a short course of clarithromycin versus placebo and were followed up for 2.6 years. The pertinent hospital records and death certificates had originally been evaluated by the adjudication committee using common definitions of outcomes mapped into a 6-category list. We now mechanically converted the International Classification of Diseases–coded diagnoses of the public registries into the same categories. After cross-tabulation of the committee diagnoses with National Patient Register diagnoses and Register of Causes of Death, we calculate agreement and compare the estimated intervention effects of the 2 data sets.

Results

With public register data, the protocol-specified categories were slightly more frequent. Overall agreement was 74% for hospital discharges and 60% for cause of death, but the intervention effect, expressed as a hazard ratio, stayed within 4% of the value originally obtained with the adjudication committee (P≥ .35).

Conclusions

Our results show a modest agreement between formal adjudication and outcomes deducible from public registers. However, the estimated intervention effect did not differ noticeably between the 2 data sources. If studies on a wide range of public registers confirm these findings, register outcomes may be considered as a replacement for adjudication committees.

Section snippets

Methods

The CLARICOR trial (ControlledTrials.gov NCT00121550) is a randomized, placebo-controlled, multicenter trial including 4,372 patients with stable coronary heart disease, using central randomization and blinding of all parties in all phases. All patients in Copenhagen with a hospital diagnosis of myocardial infarction or angina pectoris (International Classification of Diseases [ICD] codes I 20.9-21.9) during the years 1993 to 1999 were identified and, if alive, invited by mail in late 1999.

Results

During the follow-up period, 5,475 hospital discharges (type 1 events) and 384 deaths (types 2 and 3 events) occurred, out of which the RCD had no information on cause of death in 8 patients. Table I shows how each category is reproduced by the registers (liberal approach); the supplementary tables give the analogous features of the restrictive approach (online Appendix Supplementary Table I) and present the underlying complete 6-by-6 tables (online Supplementary Table II, Supplementary Table

Discussion

In patients with stable coronary heart disease participating in a randomized clinical trial where the health care contacts of the patients were traceable through existing public registries throughout follow-up, we observed that a literal, mechanical reading of ICD-coded register diagnoses would have produced nearly the same trial results as procurement of all underlying documents and dedicated assessment thereof by an AC. Specifically, the hazard ratios for the 3 protocol composite outcomes

Conclusions

All public or local registers are unique, and the quality of registers as seen from a research viewpoint varies greatly. The present study clearly demonstrates the ability of the health care system in Denmark, and presumably in other Scandinavian countries, to maintain accurate and complete public registers that may be used for research purposes. It is undoubtedly necessary to perform studies similar to ours before a clinical trial or an extended follow-up thereof can convincingly rely on

Disclosures

Funding: This study was funded by The Copenhagen Trial Unit, Center for Clinical Intervention Research. No extramural funding was used to support this work.

Conflict of Interest: None declared.

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