Table 3.
Rate of death according to serum potassium by eGFR stratum
| Variable | Serum K+ Level | Omnibus P Value | ||||||
|---|---|---|---|---|---|---|---|---|
| <3.5 mEq/L | 3.5–3.9 mEq/L | 4.0–4.4 mEq/L | 4.5–4.9 mEq/L | 5.0–5.4 mEq/L | 5.5–5.9 mEq/L | ≥6.0 mEq/L | ||
| eGFR<30 ml/min per 1.73 m2 | ||||||||
| Deaths, n | 32 | 94 | 212 | 277 | 175 | 63 | 39 | |
| Patient-years | 126 | 726 | 2211 | 3160 | 2121 | 699 | 164 | |
| Crude ratea (95% CI) | 0.26 (0.18 to 0.36) | 0.13 (0.11 to 0.16) | 0.10 (0.08 to 0.11) | 0.09 (0.08 to 0.10) | 0.08 (0.07 to 0.10) | 0.09 (0.07 to 0.12) | 0.24 (0.18 to 0.32) | |
| Adjusted IRRb,c (95% CI) | 2.77 (1.89 to 4.06) | 1.30 (1.02 to 1.66) | 1.05 (0.87 to 1.26) | Ref | 1.01 (0.83 to 1.22) | 1.11 (0.84 to 1.47) | 3.08 (2.17 to 4.37) | <0.001 |
| eGFR 30–39 ml/min per 1.73 m2 | ||||||||
| Deaths, n | 35 | 130 | 297 | 310 | 152 | 50 | 8 | |
| Patient-years | 225 | 1681 | 5694 | 6984 | 3636 | 873 | 137 | |
| Crude ratea (95% CI) | 0.16 (0.11 to 0.22) | 0.08 (0.07 to 0.09) | 0.05 (0.05 to 0.06) | 0.04 (0.04 to 0.05) | 0.04 (0.04 to 0.05) | 0.06 (0.04 to 0.08) | 0.06 (0.03 to 0.12) | |
| Adjusted IRRb,d (95% CI) | 4.31 (2.36 to 7.89) | 1.08 (0.68 to 1.69) | 0.90 (0.64 to 1.25) | Ref | 0.73 (0.47 to 1.11) | 0.98 (0.52 to 1.88) | 2.74 (1.13 to 6.74) | 0.04 |
| eGFR 40–49 ml/min per 1.73 m2 | ||||||||
| Deaths, n | 29 | 142 | 391 | 354 | 171 | 44 | 6 | |
| Patient-years | 486 | 3845 | 12,796 | 13,612 | 5455 | 1018 | 127 | |
| Crude ratea (95% CI) | 0.06 (0.04 to 0.09) | 0.04 (0.03 to 0.04) | 0.03 (0.03 to 0.03) | 0.03 (0.02 to 0.03) | 0.03 (0.03 to 0.04) | 0.04 (0.03 to 0.06) | 0.05 (0.02 to 0.11) | |
| Adjusted IRRb,c (95% CI) | 2.52 (1.71 to 3.71) | 1.46 (1.19 to 1.78) | 1.16 (1.00 to 1.34) | Ref | 1.18 (0.99 to 1.42) | 1.68 (1.23 to 2.30) | 1.72 (0.76 to 3.86) | 0.001 |
| eGFR 50–59 ml/min per 1.73 m2 | ||||||||
| Deaths, n | 57 | 277 | 612 | 469 | 170 | 36 | 7 | |
| Patient-years | 974 | 9554 | 30,349 | 26,230 | 8701 | 1316 | 117 | |
| Crude ratea (95% CI) | 0.06 (0.05 to 0.08) | 0.03 (0.03 to 0.03) | 0.02 (0.02 to 0.02) | 0.02 (0.02 to 0.02) | 0.02 (0.02 to 0.02) | 0.03 (0.02 to 0.04) | 0.06 (0.03 to 0.13) | |
| Adjusted IRRb,d (95% CI) | 4.15 (2.66 to 6.51) | 1.74 (1.33 to 2.28) | 1.14 (0.92 to 1.42) | Ref | 1.02 (0.74 to 1.42) | 0.99 (0.49 to 2.01) | 3.90 (1.23 to 12.32) | <0.001 |
Reference group for comparison is 4.5–4.9 mEq/L. P value interaction between eGFR category and K=0.72. K+, potassium; 95% CI, 95% confidence interval; IRR, incidence rate ratio; Ref, reference.
No adjustments were taken for crude rate calculations, which are expressed as events per patient-year. A Poisson distribution was used to construct the 95% CI of the crude rate for each eGFR stratum.
IRRs were adjusted for prior hospitalization, age, sex, race/ethnicity, diabetes, congestive heart failure, coronary artery disease, cerebrovascular accident, and the use of four types of medications (loop diuretics, thiazide diuretics, renin-angiotensin-aldosterone system blockers, and nondihydropyridine calcium channel blockers). Poisson distributions were used.
Model was not adjusted for race/ethnicity.
Model was not adjusted for diabetes.