Supplementary Appendix This appendix has been provided by the authors to give readers additional information about their work. Supplement to: Solomon SD, Uno H, Lewis EF, et al. Erythropoietic response and outcomes in kidney disease and type 2 diabetes. N Engl J Med 2010;363:1146-55.
Supplementary Appendix Methods: Supplemental Statistical Analysis To determine whether baseline covariates could account for hyporesponsiveness, we included 92 baseline covariates* in a backward stepwise selection logistic regression using p < 0.2 as the selection criteria, and then assessed the predictive accuracy of all possible combinations of the remaining variables (gender, smoking status, duration of chronic kidney disease, hemoglobin, egfr, albumin, crp, potassium, transferrin saturation, white blood cell, drug allergy/sensitivity, history of cardio vascular disease, angina, coronary artery bypass graft, percutaneous coronary intervention, osteopenia/osteoporosis, use of aspirin and other antiplatelet agents, aldosterone receptor blockers, statin). For each model, we calculated each patient s predicted hyporesponsiveness score, and those patients in the highest quartile for this score were classified as predicted hyporesponsive. We then identified the model that attained the highest prediction accuracy by ten-fold cross-validation. To further assess the incremental value of the hyporesponsiveness measure on predicting outcomes, we utilized a modification of the method proposed by Pencina et al. (1) in which we calculated two risk scores from logistic regression outcome models, first using baseline covariates alone and then adding the actual measure of hyporesponsiveness, and then calculated the difference in the proportion of patients with and without events whose risk score increased when the actual hyporesponsiveness measure was added.
1. Pencina MJ, D Agostino RB, D Agostino RB Jr., Vasan RS. Evaluating the added predictive ability of a new marker: From are under the ROC curve to reclassification and beyond. Statistics in Medicine, 2008, 27: 157-212. * Original variables included in model: age, gender, race (white/non-white), weight, height, bmi, waist circumference, hip circumference, ratio of waist and hip circumference, smoking status (current or not), diastolic and systolic blood pressure, heart rate, hemoglobin, hemoglobin a1c, duration of diabetes, duration of chronic kidney disease, family history of premature coronary heart disease, alcohol intake, drug allergy/sensitivity, history of cardio vascular disease, stroke, chronic atrial fibrillation/flutter, paroxysmal atrial fibrillation, auto implantable cardioverterdefibrillator, venticular, tachycardia/fibrillation, pacemaker, hypertension, valvular heart disease, angina, coronary artery bypass graft, percutaneous coronary intervention, carotid artery, peripheral, renal artery, aortic (aneurysm repair), copd, upper and lower GI bleeding, gastroparesis, peptic ulcer disease, gastroesophageal reflux disease, dyslipidemia, thyroid disease, hyperglycemia, ketoacidosis, acute pulmonary embolism, peripheral thromboembolic event, received oral iron therapy, received IV iron therapy, polysensory neuropathy, extremity weakness, amputation, left and right foot ulcer, systemic lupus erythematosus, osteopenia/osteoporosis, osteoarthritis, hyperuricemia/gout, malignancy, atrial fibrillation, cardiac arrythmia, diabetic neuropathy, heart failure, use of anti-hypertensive, statin or other lipid lowering agents,
aspirin and other antiplatelet agents, iron medications, any for diabetes, anticoagulant, diuretics excluding loop and K sparing, aldosterone receptor blockers, statin, iron medications (intramuscular), iron medications (intravenous), iron medications (oral), iron medications (other), protein creatinine ratio, egfr, albumin, bun, crp, ferritin, urine protein, potassium, reticulocytes, transferrin saturation, total cholesterol, HDL cholesterol, platelets, triglycerides, white blood cell)
Table 1. Baseline Characteristics by Quartile of Hemoglobin Response (first month). Lowest quartile defined as hyporesponders. P- value is a comparison between all four groups. Variable Category Q1 Q2 Q3 Q4 P-value Poor Response Percent Hb Change, first month < 2% 2%-8% 8-15% 15% Median Hb Change [IQ Range] -0.2 [-0.7, 0.0] 0.5 [0.4, 0.7] 1.2 [1.0,1.4] 2.0 [1.7, 2.6] Total 471 467 467 467 -- Demographic Age [Years] Mean (SD) 67.4(11.1) 67.8(10.5) 66.7(10.2) 66.8(10.7) 0.356 Median (Q1,Q3) 68 (60,75) 68 (61,75) 67 (59,75) 68 (59,74) Female Gender 294(62.4) 286(61.2) 261(55.9) 251(53.7) 0.018 Race category BLACK 105(22.3) 100(21.4) 95(20.3) 85(18.2) 0.162 OTHER 66(14.0) 60(12.8) 85(18.2) 83(17.8)
WHITE 300(63.7) 307(65.7) 287(61.5) 299(64.0) Clinical BMI at bl (kg/m^2) Mean (SD) 32.17(8.14) 32.38(7.78) 31.54(7.00) 30.79(7.03) 0.021 Current Smoking 14(3.0) 20(4.3) 29(6.2) 37(7.9) 0.004 Medical History Cardiovascular Disease Yes 326(69.2) 288(61.7) 295(63.2) 287(61.5) 0.044 Months from diagnosis of CKD to randomization Months from diagnosis of diabetes to randomization Median (Q1,Q3) Median (Q1,Q3) 28 (12,51) 29 (10,65) 26 (9,55) 25 (10,53) 0.634 179 (82,262) 178 (86,259) 193 (120,268) 185 (103,263) 0.148 Stroke 61(13.0) 48(10.3) 63(13.5) 45(9.6) 0.170 TIA 33(7.0) 31(6.6) 25(5.4) 34(7.3) 0.646 Peripheral Arterial Disease 112(23.8) 103(22.1) 84(18.0) 102(21.8) 0.173 Myocardial Infarction 92(19.5) 87(18.6) 86(18.4) 78(16.7) 0.726 Coronary Artery Disease 223(47.3) 195(41.8) 188(40.3) 194(41.5) 0.126 Heart Failure 165(35.0) 147(31.5) 139(29.8) 139(29.8) 0.259 Cardiac Arrythmia 87(18.5) 72(15.4) 63(13.5) 61(13.1) 0.083 Atrial Fibrillation 65(13.8) 57(12.2) 35(7.5) 46(9.9) 0.011
Ventricular tachycardia, ventricular fibrillation, automatic implantable cardiac 33(7.0) 29(6.2) 34(7.3) 20(4.3) 0.22 defibrillator or Pacemaker Hypertension 436(92.6) 427(91.4) 433(92.7) 428(91.6) 0.849 CABG 83(17.6) 62(13.3) 60(12.8) 52(11.1) 0.028 Diabetic Neuropathy 224(47.6) 233(49.9) 244(52.2) 223(47.8) 0.439 Malignancy 52(11.0) 48(10.3) 38(8.1) 38(8.1) 0.301 Retinopathy 221(46.9) 216(46.3) 246(52.7) 225(48.2) 0.196 Laboratory Data Blood Pressure (mm Hg) Systolic Mean (SD) 135.4(19.1) 135.0(17.6) 136.6(19.7) 137.6(18.9) 0.071 Diastolic Mean (SD) 72.3(11.4) 71.8(11.1) 72.1(11.1) 73.3(10.6) 0.160 Heart rate Mean (SD) 72.6(11.1) 72.6(10.5) 73.0(11.2) 72.5(11.0) 0.780 Abnormal ECG (%) 311(66.0) 303(64.9) 312(66.8) 277(59.3) 0.07 Protein/creatinine ration (g/g) Median (Q1,Q3) 0.4 (0.1,2.1) 0.3 (0.1,1.8) 0.4 (0.1,1.8) 0.4 (0.1,1.9) 0.181 Estimated Glomerular Mean (SD) Filtration Rate (ml/min/1.73m^2) 35.0(11.5) 35.6(11.9) 36.3 (11.9) 35.58(11.30) 0.474
Hemoglobin- hemocue (g/dl) Mean (SD) 10.79(0.99) 10.49(0.87) 10.33(0.80) 9.90(1.03) <0.001 Hemoglobin - central lab (g/dl) Mean (SD) 10.50(0.92) 10.44(0.92) 10.36(0.93) 10.20(1.08) <0.001 albumin (g/dl) Mean (SD) 3.95(0.45) 4.00(0.43) 3.94(0.44) 3.95(0.43) 0.208 total cholesterol(mg/dl) Mean (SD) 180.5 (57.0) 175.5 (50.4) 176.6 (53.5) 173.99(47.58) 0.684 LDL cholesterol (mg/dl) Mean (SD) 92.00(41.35) 90.27(40.02) 90.64(41.09) 90.12(37.79) 0.844 creatinine (mg/dl) Mean (SD) 2.05(1.77) 1.94(0.62) 1.93(0.60) 1.98(0.77) 0.822 ferritin (ug/l) Median (Q1,Q3) 152.0 120 (61,257) 116 (63,231) 133 (72,260) (72.5,271.0) 0.013 Transferrin Saturation Mean (SD) 23.3 (10.0) 24.3 (10.7) 24.6 (8.3) 25.6 (10.3) < 0.001 hemoglobin a1c (%) Mean (SD) 7.44(1.71) 7.29(1.48) 7.38(1.50) 7.27(1.55) 0.427 potassium (mmol/l) Mean (SD) 4.62(0.65) 4.73(0.60) 4.69(0.62) 4.78(0.64) <0.001 platelets (10^9/l) Mean (SD) 247.4(85.6) 251.8(79.5) 247.4(79.7) 246.12(75.59) 0.477 Urine protein (mg/dl) Mean (SD) 113.86(197.45) 108.06(201.17) 121.22(217.81) 125.26(223.83) 0.161 reticulocytes (%) Mean (SD) 1.87(0.82) 1.89(0.81) 1.90(1.02) 1.79(0.81) 0.225 White blood cell count (10^9/l) Mean (SD) 6.85(2.22) 6.78(2.03) 6.84(2.08) 6.86(2.19) 0.934 C-Reactive Protein Median (Q1,Q3) 3.2 (3.0, 7.8) 3.2(3.0, 7.2) 3.0 (3.0, 5.9) 3.0 (3.0, 5.2) < 0.001 (mg/dl)(standard assay*) Blood Urea Nitrogen (mg/dl) Mean (SD) 42.62(18.85) 42.19(16.48) 41.21(15.94) 42.16(16.86) 0.91 Medication Anti-hypertensive 457(97.0) 453(97.0) 452(96.8) 444(95.1) 0.304 Statin or other lipid lowering 288(61.1) 313(67.0) 310(66.4) 293(62.7) 0.177
agents Aspirin and other antiplatelet agents 219(46.5) 245(52.5) 224(48.0) 218(46.7) 0.225 Iron medications 205(43.5) 184(39.4) 211(45.2) 225(48.2) 0.054 Drugs used in diabetes 424(90.0) 420(89.9) 420(89.9) 418(89.5) 0.994 ACEi or ARB 361(76.6) 378(80.9) 385(82.4) 377(80.7) 0.141 Diuretics - loop 273(58.0) 261(55.9) 271(58.0) 254(54.4) 0.622 Diuretics - K sparing 46(9.8) 26(5.6) 25(5.4) 22(4.7) 0.006 Aldosterone receptor blockers 40(8.5) 22(4.7) 22(4.7) 20(4.3) 0.015 Statin 259(55.0) 292(62.5) 286(61.2) 277(59.3) 0.096 Other lipid lowering agents 79(16.8) 70(15.0) 76(16.3) 63(13.5) 0.508 Aspirin 195(41.4) 210(45.0) 197(42.2) 192(41.1) 0.620 Other antiplatelet agents 53(11.3) 66(14.1) 61(13.1) 58(12.4) 0.606 Insulin 237(50.3) 233(49.9) 234(50.1) 212(45.4) 0.372 Oral anti-diabetic agents 260(55.2) 274(58.7) 264(56.5) 281(60.2) 0.422 Vitamin K antagonists 41(8.7) 32(6.9) 29(6.2) 26(5.6) 0.256 Aspirin or platelet aggregation inhibitors or vitamin K antagonists 250(53.1) 269(57.6) 242(51.8) 239(51.2) 0.193 Insulin Use 237(50.3) 233(49.9) 234(50.1) 212(45.4) 0.37 * all less than assay values for c-reactive protein were reported as 3.0 mg/dl
TREAT Dosing Algorithm Subjects in both arms received investigational product (darbepoetin alfa or placebo) by subcutaneous injection. All dose assignments were managed using an interactive voice response system (IVRS) which utilized a pre-specified dosing algorithm based on the subject s hemoglobin and rate of rise. Darbepoetin alfa Arm This algorithm was designed to titrate the dose of the darbepoetin alfa group to maintain hemoglobin levels at approximately 13 g/dl, taking into account both rate of rise and stability of hemoglobin levels. Initially, study drug was administered every two weeks but once a hemoglobin level between 12.0 and 13.5 g/dl was maintained with no dosage adjustments, the frequency of drug administration was extended to monthly with the dosage doubled. To maintain blinding, the IVRS assigned comparable changes to placebo patients (Appendix C). The initial dose of darbepoetin alfa for each subject in the treatment arm was 0.75 μg/kg. Doses were adjusted as necessary to maintain a hemoglobin of 13 g/dl. Dose increases did not occur more frequently than once monthly. The protocol specified a maximum monthly dose of 600 μg. Doses were initially administered once every 2 weeks, however, once a subject had achieved 2 consecutive hemoglobin levels within 12.0 13.5 g/dl, with no change in dose, the frequency of administration was extended to once monthly, with the initial once monthly dose of darbepoetin alfa equal to twice the previous every 2-week dose. Subjects receiving the lowest dose of darbepoetin alfa every 2 weeks who required a dose decrease, also had their dosing interval extended to monthly. If a subject was unable to maintain the hemoglobin target while on the monthly dosing regimen, the subject was reverted back to the once every 2 week dosing frequency. Placebo Arm To prevent unblinding, an IVRS algorithm ensured that the dosing frequency schedule changes occurring in the darbepoetin alfa arm were mirrored in the placebo arm. If at any time a placebo subject s hemoglobin fell below 9.0 g/dl, rescue therapy with darbepoetin alfa was initiated with a single dose of 0.45 μg/kg. Rescue therapy continued to be assigned per a predefined dosing algorithm until the subject s hemoglobin reached 9.0 g/dl, at which time placebo injections were resumed.
Darbepoetin alfa Dosing Algorithm Hb (g/dl) Hb rate of rise (g/dl/2 weeks) Dose Adjustment < 0.5 Increase to next higher dose < 12.5 0.5 - < 1.0 Maintain dose 1.0 Decrease to next lower dose < 0.5 Maintain dose 12.5 - < 13.5 0.5 - < 1.0 Maintain dose 1.0 Decrease to next lower dose 13.5-14.0 Any Decrease to next lower dose > 14.0 Any Administer placebo until Hb value is below 13.0, then resume darbepoetin alfa at next lower dose Rescue Therapy Dosing Algorithm Hb (g/dl) Hb rate of rise (g/dl/2 weeks) Dose Adjustment < 9.0 < 0.5 Initiate or increase to next higher dose < 9.0 0.5, but < 1.0 Maintain dose < 9.0 1.0 Decrease to next lower dose 9.0 Any Resume placebo administration