Table 1

Baseline characteristics for patients in the Emergency Department and Hospitalised Cohorts

Emergency Department Cohort (n=36049)Hospitalised Cohort (n=38566)
Demographics
 Median age (IQR), years77 (72–83)76 (71–82)
 Women (n (%))19262 (53.4)19070 (49.4)
Income Quintile(n (%))
 One (lowest)7678 (21.3)8027 (20.8)
 Two7306 (20.3)7765 (20.1)
 Three (middle)7062 (19.6)7654 (19.8)
 Four6110 (16.9)6797 (17.6)
 Five (highest)7301 (20.3)7816 (20.3)
Year of Cohort Entry(n (%))
 2003–20043648 (10.1)6733 (17.5)
 2005–20068348 (23.2)9256 (24.0)
 2007–200811954 (33.2)11380 (29.5)
 2009–201012099 (33.6)11197 (29.0)
Rural location(n (%))5397 (15.0)7165 (18.6)
Resident in a long-term care facility(n (%))1454 (4.0)1298 (3.4)
Comorbidities* (n (%))
 Chronic kidney disease†1526 (4.2)1632 (4.2)
 Diabetes mellitus‡8497 (23.6)8650 (22.4)
 Peripheral vascular disease1137 (3.2)2077 (5.4)
 Coronary artery disease§16847 (46.7)18844 (48.9)
 Congestive heart failure8860 (24.6)9224 (23.9)
 Stroke/transient ischaemic attack1434 (4.0)1467 (3.8)
 Chronic liver disease837 (2.3)1074 (2.8)
Medication Use* (n (%))
 Angiotensin-converting enzyme inhibitor13781 (38.2)14859 (38.5)
 Angiotensin-receptor blocker6540 (18.1)6514 (16.9)
 Potassium sparing diuretic3643 (10.1)3949 (10.2)
 Non-potassium sparing diuretic16308 (45.2)17145 (44.5)
 Calcium channel blocker11785 (32.7)12553 (32.5)
 β-Adrenergic antagonist13646 (37.9)14662 (38.0)
 Statins15706 (43.6)16602 (43.0)
 NSAIDs (excluding aspirin)6520 (18.1)7761 (20.1)
 Anticonvulsants2297 (6.4)2244 (5.8)
 Antidepressants9187 (25.5)8938 (23.2)
 Antipsychotics1883 (5.2)1692 (4.4)
 Benzodiazepines9035 (25.1)9414 (24.4)
 Antineoplastics2217 (6.1)2377 (6.2)
 Thyroid hormone6172 (17.1)6150 (15.9)
Baseline laboratory measurements¶
Serum creatinine concentration, µmol/L, median (IQR)91 (75–113)90 (75–114)
 eGFR ml/min/1.73 m2,** median (IQR)61 (46–75)62 (47–77)
eGFR category(n (%))
 ≥60 ml/min/1.73 m218382 (51.0)20716 (53.7)
 45–59 ml/min/1.73 m29043 (25.1)9011 (23.4)
 30–44 ml/min/1.73m25622 (15.6)5633 (14.6)
 15–29 ml/min/1.73m22415 (6.7)2537 (6.6)
 <15 ml/min/1.73m2587 (1.6)669 (1.7)
Urine dipstick protein(n (%))
 negative4186 (84.0)3252 (81.4)
 0.3g/l415 (8.3)409 (10.2)
 1.0g/l296 (5.9)257 (6.4)
 ≥3.0g/l87 (1.7)79 (2.0)
Serum sodium concentration, mmol/l, median (IQR)139 (137–142)139 (137–141)
Serum potassium concentration, mmol/l, median (IQR)4.0 (4.0–5.0)4.0 (4.0–5.0)
AKI definitions for all patients(n (%))
 AKIN Stage 1 or greater5312 (14.7)6879 (17.8)
 RIFLE Risk473 (1.3)884 (2.3)
 RIFLE Injury294 (0.8)567 (1.5)
 RIFLE Failure527 (1.5)920 (2.4)
AKI definitions for patients with CKD† (n (%))
 AKIN Stage 1 or greater524 (34.3)644 (39.5)
 RIFLE Risk25 (1.6)65 (4.0)
 RIFLE Injury12 (0.8)41 (2.5)
 RIFLE Failure154 (10.1)246 (15.1)
  • *Comorbidities and medication usage in the 5 and 6 months preceding the hospital encounter were considered, respectively.

  • †CKD was assessed by the ICD-10 code N18×, defined as ‘chronic kidney disease’.

  • ‡Diabetes mellitus was assessed by the diabetic medication use in the previous 6 months.

  • §Coronary artery disease includes the receipt of coronary artery bypass graft surgery, percutaneous coronary intervention and diagnoses of angina.

  • ¶The baseline measurements for serum creatinine were taken at a median (IQR) of 102 (41–204) and 39 (16–128) days prior to the hospital encounter for the Emergency Department Cohort and the Hospitalised Cohort, respectively. Baseline urine protein and serum sodium and potassium were available for a subset of patients. Emergency Department cohort: A total of 4984, 29 746 and 30 040 patients had a baseline urine protein and serum sodium and potassium measurement available in the 7 to 365 days prior to the index date, respectively. Hospitalised cohort: A total of 3997, 34 407 and 34 538 patients had a baseline urine protein and serum sodium and potassium measurements available in the 7–365 days prior to the index date, respectively

  • **eGFR was calculated using the CKD-Epi equation.

  • CKD-Epi equation:141×min((serum creatinine in μmol/L/88.4)/κ, 1)α×max((serum creatinine in μmol/L/88.4)/κ, 1)−1.209×0.993Age×1.018 (if female)×1.159 (if an African–American) κ=0.7 for females and 0.9 for males, α=−0.329 for females and −0.411 for males, min=the minimum of Scr/κ or 1, max=the maximum of Scr/κ or 1. Racial information was not available in our data sources and all patients were assumed not to be of a non African–Canadian race. This was a reasonable assumption; as of 2006, African–Canadians represented less than 7% of the Ontario population. Source: http://www12.statcan.ca/census-recensement/2006/dp-pd/hlt/97-562/index.cfm?Lang=E

  • eGFR, estimated glomerular filtration rate.