Patients were enrolled from an ancillary study of COPES (Coronary Psychosocial Patient Evaluation Study), a multisite, observational cohort study designed to investigate the aetiology and naturalistic course of depressive symptoms in the three‐month period after an ACS event. Patients were eligible for inclusion in COPES if they had been hospitalised for an ACS event (either acute myocardial infarction with or without ST segment elevation or unstable angina) and scored between 0 and 4 (indicative of no depressive symptoms) or
10 (at least mild depressive symptoms) on the Beck Depression Inventory (BDI) within one week after the index ACS event. The BDI is a self‐report measure of depressive symptom severity, and a score of
10 is associated with increased mortality risk after an ACS event.5
The BDI was readministered three months after enrolment.
Of the 275 patients enrolled in the COPES parent study between May 2003 and May 2005, 162 (58.9%) consented to a substudy in which blood was drawn to assess CRP concentrations at baseline and at the three‐month follow up. Substudy participants did not differ from non‐participants on age, sex, baseline depression score and several clinical variables (p > 0.20) (table 1 lists the variables). Of the 162 participants, 59 (36.4%) did not get their blood drawn at three months: 50 patients (30.9%) were lost to follow up, 5 (3.0%) declined follow up and 4 (2.5%) died.
Table 1Group characteristics
As the primary objective of this study was to determine the relation between CRP concentration and depression remission status over time, patients were classified into three comparison groups: persistently depressed (BDI score
10 at baseline and after three months), remittently depressed (BDI score
10 at baseline and < 10 after three months) and persistently non‐depressed (BDI score 0–4 at baseline and < 10 after three months).
After centrifugation, serum samples were stored in aliquot portions at −70°C until they were shipped to a core laboratory (Specialty Laboratories, Valencia, California, USA) for analysis of high sensitivity CRP concentrations. Concentrations of CRP were determined by turbidimetry (Bayer Diagnostics, Leverkusen, Germany). We divided CRP concentrations into two categories:
3 mg/l and > 3 mg/l as previously described.1
A cut off of 3 mg/l identifies a group at increased risk for recurrent events and death after an ACS event.1
Written informed consent was obtained from all participants, and the study was approved by the research ethics committees of the three university‐affiliated hospitals from which the participants were recruited (Mount Sinai Hospital, New York, New York; University of Medicine & Dentistry of New Jersey, New Jersey; and Yale–New Haven Hospital, New Haven, Connecticut, USA).
Differences in baseline characteristics between groups and differences in CRP concentrations in depression groups were analysed by univariate analyses of variance or χ2 analyses. To test for the impact of potential confounders that were specified a priori, a hierarchical logistic regression analysis was conducted. We used two‐tailed tests of significance and SPSS statistical software (V.12.0; SPSS Inc, Chicago, Illinois, USA).