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Table 2 Patients with complete and incomplete follow-up data stratified for CKD onset; values are numbers (%) unless indicated otherwise

From: An external validation of models to predict the onset of chronic kidney disease using population-based electronic health records from Salford, UK

Parameters No CKD CKD
Patients with complete follow-up Patients with incomplete follow-up
  Missing   Missing   Missing
Included patients 156,615 None 172,361 None 6038 None
Died before developing CKD 719 (0.5) None 6941 (4) None / None
Follow-up (mean, SD) 5.6 (0.2) None 5.4 (0.7) None 2.6 (1.7) None
Age (mean, SD) 42.1 (16.7) None 42.7 (17.3) None 70.3 (12.5) None
Female sex 82,883 (52.9) None 89,389 (51.9) None 3452 (57.2) None
Townsend index (mean, SD)e 1.6 (3.5) 2900 (1.9) 1.6 (3.4) 3244 (1.9) 1.4 (3.4) 47 (0.8)
Ethnicity Not recorded 55,586 (35.6) Not applicabled 61,220 (35.6) Not applicabled 2014 (33.4) Not applicabled
White 90,443 (57.8) 99,243 (57.7) 3889 (64.5)
Other 10,586 (6.8) 11,898 (6.9) 135 (2.2)
Smokinge Non-smoker 66,769 (48.8) 19,901 (12.7) 72,137 (48.4) 23,296 (13.5) 2167 (37.7) 292 (4.8)
Ex-smoker 29,980 (21.9) 33,097 (22.2) 2475 (43.1)
Light smoker (1–9 cg/day) 11,072 (8.1) 12,128 (8.1) 344 (6)
Moderate smoker (10–19 cg/day) 16,951 (12.4) 18,472 (12.4) 413 (7.2)
Heavy smoker (≥ 20 cg/day) 11,942 (8.7) 13,231 (8.9) 347 (6)
BMI, kg/m2 (mean, SD)e 26.6 (6) 33,717 (21.5) 28 (6.1) 38,628 (22.4) 28.4 (6) 518 (8.6)
Diastolic blood pressure, mmHg (mean, SD)e 76.9 (9.8) 75,616 (48.3) 78.9 (10.2) 85,075 (49.4) 75.8 (10.2) 1164 (19.3)
Systolic blood pressure, mmHg (mean, SD)e 128.2 (15.8) 75,602 (48.3) 130.5 (16.7) 85,058 (49.3) 136.3 (16.7) 1166 (19.3)
eGFR, mL/min/1.73 m2 (mean, SD) 83.7 (9.4) 118,912 (75.9) 82.5 (9.4) 131,103 (76.1) 69.4 (11.3) 1828 (30.3)
Hb, g/dLe 13.9 (1.6) 110,723 (70.7) 13.8 (1.6) 122,430 (71) 13.4 (1.7) 2530 (41.9)
Proteinuriaa,b 751 (0.5) 149,234 (95.3) 18 (0.2) 164,097 (95.2) 236 (3.9) 4665 (77.3)
Quantitative albuminuriab,c 129 (0.1) 152,266 (97.2) 4 (0) 167,482 (97.2) 62 (1) 5167 (85.6)
HDL cholesterol levelb, mg/dL (mean, SD) 25.9 (7.9) 122,477 (78.2) 26.7 (7.9) 135,066 (78.4) 25.7 (7.8) 2413 (40)
  1. BMI, body mass index; cg, cigarettes; CKD, chronic kidney disease; eGFR, estimated glomerular filtration rate; HDL, high-density lipoprotein; MDRD, modification of diet in renal disease; SD, standard deviation
  2. aAlbumin:creatinine ratio >30 mg/mmol or albumin concentration >200 mg/L, or diagnostic code
  3. bVariable excluded as predictor from external validation due to >70 % missing values
  4. cAlbumin:creatinine ratio >30 mg/mmol
  5. dPatients without recorded ethnicity were considered as white (see Methodssection)
  6. eMultiple imputation applied to missing values