Background
Methods
Population
Outcomes – Unplanned readmission or death within 90 days
Follow up
Covariates and candidate predictors
AKI criteria | Definition |
---|---|
Index AKI episode (lasting up to 90 days in duration) | Serum creatinine ≥1.5 times higher than the median of all creatinine values 8-90 days ago; or 91–365 days ago if no tests between 8 and 90 days; or serum creatinine ≥1.5 times higher than the lowest creatinine within 7 days; or serum creatinine >26 μmol/L higher than the lowest creatinine within 48 h |
Prior AKI episode | Any episode occurring 91-1095 days prior to index episode |
Statistical analyses
Assessment of model performance
Model application
Results
Cohort characteristics
90 day readmission or death (%) | 90 day readmission free survival (%) baseline impairment | Univariable odds ratio (95% CI) | ||||
---|---|---|---|---|---|---|
N | 3065 | 13388 | ||||
Age (median, IQR) | 74 | (62–83) | 69 | (55–79) | 1.20 (/10 years) | (1.17–1.23) |
Male sex | 1372 | (44.8) | 5770 | (43.1) ()) | 1.07 | (0.99–1.16) |
Residential care | 277 | (9.0) | 471 | (3.5) | 2.72 | (2.34–3.18) |
Deprived (highest quintile) | 298 | (9.7) | 1088 | (8.1) | 1.22 | (1.06–1.39) |
Rural (settlement <3000) | 735 | (24.0) | 3720 | (27.8) | 0.82 | (0.75–0.90) |
Admission context | ||||||
No admissions past yeara
| 1896 | (61.9) | 10461 | (78.1) | 1.38 (/admission) | (1.34–1.43) |
1 admission past year | 593 | (19.3) | 1872 | (14.0) | ||
2 admissions past year | 244 | (8.0) | 620 | (4.6) | ||
3+ admissions past year | 332 | (10.8) | 435 | (3.2) | ||
Length of stay (median, IQR) | 7 | (2–16) | 3 | (1–9) | 1.05 (/7 days) | (1.04–1.06) |
Emergency admission | 2326 | (75.9) | 7760 | (58.0) | 2.28 | (2.09–2.50) |
Medical ward admission | 1889 | (61.6) | 6570 | (49.1) | 1.67 | (1.54–1.81) |
Intensive care admission | 98 | (3.2) | 366 | (2.7) | 1.18 | (0.94–1.47) |
Renal function | ||||||
No AKI | 2154 | (70.3) | 11676 | (87.2) | (reference group) | |
AKI stage 1 | 528 | (17.2) | 1190 | (8.9) | 2.41 | (2.15–2.69) |
AKI stage 2 | 233 | (7.6) | 341 | (2.5) | 3.70 | (3.12–4.40) |
AKI stage 3 | 150 | (4.9) | 181 | (1.4) | 4.49 | (3.60–5.60) |
No prior AKI episodesa
| 2526 | (82.4) | 12188 | (91.0) | 1.71 (/episode) | (1.58–1.85) |
1 prior AKI episode | 414 | (13.5) | 1000 | (7.5) | ||
2+ prior AKI episodes | 125 | (4.1) | 200 | (1.5) | ||
Baseline eGFR (median, IQR)a
| 63 | (48–83) | 66 | (52–87) | 0.94 (/10 ml/min/1.73 m2) | (0.93–0.96) |
Baseline eGFR 0–29 | 213 | (6.9) | 502 | (3.7) | ||
Baseline eGFR 30–44 | 423 | (13.8) | 1461 | (10.9) | ||
Baseline eGFR 45–59 | 713 | (23.3) | 3309 | (24.7) | ||
Baseline eGFR ≥60 | 1716 | (56.0) | 8116 | (60.6) | ||
Discharge creatinine 20% > baseline | 520 | (17.0) | 1167 | (8.7) | 2.14 | (1.91–2.39) |
Comorbidity | ||||||
Cancer | 410 | (13.4) | 973 | (7.3) | 1.97 | (1.74–2.23) |
Cardiac failure | 317 | (10.3) | 592 | (4.4) | 2.49 | (2.16–2.88) |
Cerebrovascular disease | 231 | (7.5) | 580 | (4.3) | 1.80 | (1.54–2.11) |
Dementia | 96 | (3.1) | 163 | (1.2) | 2.62 | (2.03–3.39) |
Diabetes | 336 | (11.0) | 776 | (5.8) | 2.00 | (1.75–2.29) |
Hemiplegia | 28 | (0.9) | 71 | (0.5) | 1.73 | (1.11–2.68) |
Liver disease | 59 | (1.9) | 156 | (1.2) | 1.66 | (1.23–2.25) |
Myocardial infarction | 257 | (8.4) | 638 | (4.8) | 1.83 | (1.57–2.13) |
Peptic ulcer disease | 81 | (2.6) | 278 | (2.1) | 1.28 | (1.00–1.64) |
Peripheral vascular disease | 162 | (5.3) | 452 | (3.4) | 1.60 | (1.33–1.92) |
Pulmonary disease | 346 | (11.3) | 704 | (5.3) | 2.29 | (2.00–2.62) |
Rheumatic disease | 82 | (2.7) | 289 | (2.2) | 1.25 | (0.97–1.60) |
Reasons for readmission after AKI
Relationship between AKI and unplanned readmission or death
AKI as an independent predictor of unplanned readmission or death
Full model | Best stepwise model | ||||||
---|---|---|---|---|---|---|---|
OR | 95% CI |
p-value | OR | 95% CI |
p-value | Variable Inclusion %b
| |
Characteristics | |||||||
Age (per 10 years) | 1.19 | (1.14–1.24) | <0.001 | 1.17 | (1.13–1.21) | <0.001 | 100 |
Age term squared | 1.00 | (0.99–1.02) | 0.388 | 12.4 | |||
Male sex | 1.08 | (1.00–1.18) | 0.061 | 26.4 | |||
Residential care | 1.63 | (1.36–1.94) | <0.001 | 1.37 | (1.42–1.98) | <0.001 | 100 |
Deprived (highest vs all other quintiles) | 1.11 | (0.96–1.29) | 0.150 | 15.4 | |||
Rural (settlement <3000) | 0.88 | (0.80–0.97) | 0.008 | 0.86 | (0.78–0.94) | 0.001 | 65.2 |
Admission context | |||||||
Admissions in prior 1 year (per admission) | 1.21 | (1.17–1.25) | <0.001 | 1.23 | (1.18–1.27) | <0.001 | 100 |
Length of stay (per week) | 0.99 | (0.98–1.00) | 0.242 | 7.0 | |||
Emergency admission | 1.81 | (1.64–2.01) | <0.001 | 1.89 | (1.72–2.08) | <0.001 | 100 |
Medical ward admission | 1.09 | (0.99–1.19) | 0.066 | 24.6 | |||
Intensive care admission | 0.88 | (0.68–1.13) | 0.308 | 5.2 | |||
Renal function | |||||||
No AKI | (reference group) | ||||||
AKI stage 1 | 1.57 | (1.36–1.80) | <0.001 | 1.50 | (1.33–1.70) | <0.001 | 100 |
AKI stage 2 | 2.35 | (1.92–2.88) | <0.001 | 2.23 | (1.85–2.68) | <0.001 | 100 |
AKI stage 3 | 2.95 | (2.29–3.80) | <0.001 | 2.80 | (2.22–3.53) | <0.001 | 100 |
Prior AKI count (per episode) | 1.11 | (1.02–1.22) | 0.020 | 47.4 | |||
Baseline eGFR linear terma
| 0.89 | (0.82–0.96) | 0.005 | 0.87 | (0.80–0.94) | <0.001 | |
Baseline eGFR squared terma
| 1.01 | (1.00–1.02) | 0.001 | 1.01 | (1.01–1.02) | <0.001 | 91.0 |
Discharge creatinine 20% > baseline | 0.93 | (0.80–1.08) | 0.317 | 6.0 | |||
Comorbidity | |||||||
Cancer | 1.59 | (1.38–1.82) | <0.001 | 1.59 | (1.37–1.82) | <0.001 | 100 |
Cardiac failure | 1.32 | (1.12–1.55) | 0.001 | 1.42 | (1.21–1.66) | <0.001 | 88.8 |
Cerebrovascular disease | 1.07 | (0.89–1.27) | 0.471 | 6.0 | |||
Dementia | 1.21 | (0.92–1.60) | 0.174 | 13.2 | |||
Diabetes | 1.33 | (1.15–1.54) | <0.001 | 1.38 | (1.19–1.60) | <0.001 | 92.0 |
Hemiplegia | 0.91 | (0.56–1.47) | 0.691 | 0.4 | |||
Liver disease | 1.19 | (0.86–1.66) | 0.299 | 11.2 | |||
Myocardial infarction | 1.13 | (0.95–1.33) | 0.170 | 13.6 | |||
Peptic ulcer disease | 0.90 | (0.69–1.18) | 0.464 | 2.0 | |||
Peripheral vascular disease | 1.00 | (0.82–1.22) | 0.994 | 0.6 | |||
Pulmonary | 1.44 | (1.24–1.67) | <0.001 | 1.47 | (1.27–1.70) | <0.001 | 99.2 |
Rheumatic disease | 0.92 | (0.70–1.20) | 0.525 | 2.4 |
Performance of prediction models
Full model | Best stepwise model | Administrative data only model | Biochemistry + age model | Age alone model | AKI alone | |
---|---|---|---|---|---|---|
Characteristics | ||||||
Age | * | * | * | * | * | |
Age term quadratic term | * | * | * | |||
Male sex | * | |||||
Residential care | * | * | * | |||
Deprived (highest quintile) | * | |||||
Rural (settlement <3000) | * | * | * | |||
Admission context | ||||||
Admissions in prior 1 year (per admission) | * | * | * | |||
Length of stay (per week) | * | |||||
Emergency admission | * | * | * | |||
Medical ward admission | * | * | ||||
Intensive care admission | * | |||||
Renal function | ||||||
AKI stages 0–3 | * | * | * | * | ||
Prior AKI count (per episode) | * | * | ||||
Baseline eGFR (linear and quadratic) | * | * | * | |||
Discharge creatinine 20% > baseline | * | |||||
Comorbidity | ||||||
Cancer | * | * | * | |||
Cardiac failure | * | * | * | |||
Cerebrovascular disease | * | |||||
Dementia | * | |||||
Diabetes | * | * | * | |||
Hemiplegia | * | |||||
Liver disease | * | |||||
Myocardial infarction | * | |||||
Peptic ulcer disease | * | |||||
Peripheral vascular disease | * | |||||
Pulmonary | * | * | * | |||
Rheumatic disease | * | |||||
Model C statistic | 0.699 | 0.698 | 0.685 | 0.655 | 0.594 | 0.587 |
95% confidence interval | (0.688–0.709) | (0.688–0.709) | (0.675–0.696) | (0.644–0.666) | (0.582–0.605) | (0.578–0.596) |
P-value for AUC comparison with the next most complex model | - | 0.536 | <0.001 | <0.001 | <0.001 | 0.344 |