Table 1
Bivariable association of the baseline characteristics of study patients with the outcomes.
| Characteristic | Outcome at the end of six months | P value | ||
|---|---|---|---|---|
| No event (n = 141) | MACE only (n = 28) | Death/MACE (n = 31 | ||
| Age [Mean (SD)], y | 54.63 (12.31) | 62.46 (14.21) | 61.39 (13.12) | 0.0013a |
| Males [n (%)] | 109 (77.30) | 13 (46.43) | 16 (51.61) | 0.0004b |
| Body mass index [Mean (SD)], Kg/m2 | 22.39 (2.11) | 22.09 (2.30) | 22.17 (2.22) | 0.6825a |
| Waist/Hip Ratio [Mean (SD)] | 0.91 (0.05) | 0.90 (0.05) | 0.91 (0.05) | 0.7296a |
| Overweight—BMI ≥25 Kg/m2 [n (%)] | 15 (10.64) | 3 (10.71) | 4 (12.90) | 0.9369c |
| Number of Personal Risk factors [n (%)]d | 0.4696c | |||
| 0 | 65 (46.10) | 19 (67.86) | 17 (54.84) | |
| 1 | 42 (29.79) | 5 (17.86) | 7 (22.58) | |
| 2 | 21 (14.89) | 3 (10.71) | 6 (19.35) | |
| 3 | 13 (9.22) | 1 (3.57) | 1 (3.23) | |
| Killip class [n (%)] | 3.70 × 10–14c | |||
| I | 76 (53.90) | 8 (28.57) | 2 (6.45) | |
| II | 61 (43.26) | 11 (39.29) | 11 (35.48) | |
| III | 4 (2.84) | 9 (32.14) | 15 (48.39) | |
| IV | 0 (0.00) | 0 (0.00) | 3 (9.68) | |
| Acute coronary syndrome type [n (%)]e | 0.3608 | |||
| STEMI | 92 (62.25) | 20 (71.43) | 26 (83.87) | |
| NSTEMI | 6 (4.26) | 1 (3.57) | 1 (3.23) | |
| UA | 43 (30.50) | 7 (25.00) | 4 (12.90) | |
| Comorbidities [n (%)] | ||||
| Diabetes | 106 (75.18) | 17 (60.71) | 18 (58.06) | 0.0790b |
| Hypertension | 86 (60.99) | 13 (46.43) | 15 (48.39) | 0.2089b |
| TIA/Stroke | 0 (0.00) | 2 (7.14) | 3 (9.68) | 0.0020c |
| Heart failure | 1 (0.71) | 3 (10.71) | 3 (9.68) | 0.0041c |
| Cardiovascular disease | 41 (29.08) | 4 (14.29) | 6 (19.35) | 0.1809b |
| Clinical chemistry at baseline | ||||
| Hemoglobin [Mean (SD)], g/dl | 12.94 (1.89) | 10.16 (1.70) | 9.77 (2.59) | 1.90 × 10–17a |
| Anemia [n (%)] | 63 (44.68) | 26 (92.86) | 28 (90.32) | 6.72 × 10–9b |
| Serum albumin [Mean (SD)], g/dl | 4.38 (0.41) | 4.51 (0.45) | 4.50 (0.44) | 0.1411a |
| Serum creatinine [Mean (SD)], mg/dl | 1.23 (0.18) | 1.27 (0.17) | 1.25 (0.22) | 0.5892a |
| Serum creatine-kinase MB [Mean (SD)], IU | 69.11 (8.07) | 68.46 (13.41) | 72.97 (10.32) | 0.9731a |
| Medication use [n (%)] | ||||
| Aspirin | 121 (85.82) | 20 (71.43) | 23 (74.19) | 0.0911b |
| β-blockers | 105 (74.47) | 15 (53.57) | 19 (61.29) | 0.0489b |
| Statins | 110 (78.01) | 21 (75.00) | 18 (58.06) | 0.0697b |
| Angiotensin receptor blockers | 16 (11.35) | 2 (7.14) | 0 (0.00) | 0.1256c |
| ACE inhibitors | 53 (37.59) | 7 (25.00) | 4 (12.90) | 0.0163c |
| Spironolactone | 6 (4.26) | 0 (0.00) | 1 (3.23) | 0.8357c |
| PCI done | 14 (9.93) | 3 (10.71) | 1 (3.23) | 0.4663c |
[i] a estimated using analysis of variance; b estimated using Pearson’s Χ2 test; c estimated using Fisher’s exact test; d combinations of tobacco ingestion, smoking and alcohol intake currently or in the past; e STEMI – ST elevation myocardial infarction, NSTEMI – non-ST elevation myocardial infarction, UA – unstable angina.
Table 2
Results of logistic regression analysis for the multivariable association of risk factors with the study outcomes.
| Covariate | Death within 6 months | Death/MACE within 6 months | ||
|---|---|---|---|---|
| OR (95% CI) | p | OR (95% CI) | p | |
| Full model | ||||
| Age | 0.98 (0.94–1.02) | 0.376 | 0.99 (0.96–1.03) | 0.745 |
| Males | 0.92 (0.32–2.62) | 0.869 | 0.74 (0.28–1.89) | 0.527 |
| Killip class | 11.0 (3.11–38.9) | 2.0 × 10–4 | 10.2 (2.54–40.8) | 0.001 |
| Diabetes | 1.18 (0.41–3.44) | 0.755 | 1.61 (0.64–4.06) | 0.307 |
| TIA/Stroke | 9.55 (1.01–90.17) | 0.049 | – | 0.992 |
| Heart failure | 0.93 (0.14–6.15) | 0.940 | 1.59 (0.14–18.1) | 0.709 |
| Hemoglobin | 0.70 (0.54–0.91) | 0.007 | 0.58 (0.44–0.75) | 4.9 × 10–5 |
| Aspirin use | 3.73 (0.43–32.1) | 0.230 | 0.69 (0.11–4.56) | 0.702 |
| β-blocker use | 1.56 (0.37–6.66) | 0.546 | 0.85 (0.25–2.82) | 0.792 |
| Statin use | 0.23 (0.05–0.98) | 0.046 | 1.10 (0.26–4.66) | 0.893 |
| ACE inhibitor use | 0.39 (0.10–1.47) | 0.165 | 0.67 (0.24–1.86) | 0.444 |
| Stratified propensity score adjusted model | ||||
| Hemoglobin | 0.72 (0.57–0.91) | 0.007 | 0.55 (0.43–0.72) | 5.4 × 10–6 |
[i] OR, odds ratio; CI, confidence interval.
Figure 1
Incremental value of baseline hemoglobin concentration in prognostication of ACS over the GRACE score. (A–B) Comparison of the ROC curves that predict death within 6 months (A) or death/MACE within 6 months based on GRACE score only (orange curves) or GRACE score as well as baseline hemoglobin concentration (purple curves). Difference in the areas under the two ROCs were estimated using a bootstrapping method as detailed in the Stata package comproc. Statistical significance was tested using the DeLong, DeLong and Clarke-Pearson test. AUC, area under the curve; ROC, receiver operating characteristic curve. (C) Incremental value of baseline hemoglobin concentration as assessed using the incremental discrimination improvement (IDI), relative IDI and the net reclassification index (NRI). Diamonds indicate point estimates and the error bars indicate 95% confidence intervals. All the plots are color-coded for the two study outcomes. (D) Predicted probability of the study outcomes based on a combination of the dichotomized GRACE score and presence or absence of baseline anemia.
Figure 2
Derivation of a propensity score to test the robustness of association of baseline hemoglobin concentration with study outcomes. (A) Sequential logistic regression models were used to ensure the balance of the predictors of baseline anemia across groups of patients with and without anemia. The standardized differences before and after adjustment are shown in blue and red circles, respectively. All the variables were adequately balanced after adjustment. (B) Kernel density of the propensity score across patients with and without anemia.
| ACS | acute coronary syndrome |
| GRACE | Global Registry of Acute Coronary Events |
| IDI | incremental discrimination improvement |
| LMIC | low and middle income countries |
| MACE | major adverse cardiac event |
| NRI | net reclassification index |
| OOP | optimum operating point |
| ROC | receiver operating characteristics |