Article Figures & Data
Figures
- Figure 1.
Distribution of PDP among the study cohort. On the basis of the empiric distribution, PDP was categorized according to observed quartile (indicated by dashed lines), with a separate category used to represent subjects with no prescribed restriction of dietary phosphate.
- Figure 2.
Longitudinal changes in metabolic bone disease indices according to baseline PDP. (A) Overall, serum phosphate did not change over time (P = 0.77); although serum phosphate tended to rise more in quartiles 3 (PDP 1000 mg/d) and 4 (PDP 1001 to 2000 mg/d), these differences were not statistically significant from the referent group (PDP ≤870 mg/d): P for group-by-time interaction 0.12 and 0.38, respectively. (B) Overall, serum parathyroid hormone (PTH) tended to rise over time (P = 0.03), and this slope was greater among participants with more permissive PDP: P for group by time interaction 0.01, 0.05, and 0.11 for PDP 1000, 1001 to 2000, and no-restriction groups, respectively (referent PDP ≤870 mg/d). [Because of its highly skewed distribution, PTH was analyzed on the log scale and back transformed for this figure, accounting for the curvilinear appearance.]
- Figure 3.
Use of dietary supplements over time among the categories of PDP. In these analyses, PDP was time updated to reflect the current year's prescription. P trend across PDP groups <0.001 within each year.
- Figure 4.
Association between PDP and all-cause mortality on baseline analyses. For each model, the referent group is PDP ≤870 mg/d. Multivariable models were adjusted, through application of inverse probability of treatment weights, for age, sex, race, dialysis vintage, access type, eKt/V, diabetes, congestive heart failure, arterial disease, serum albumin, serum creatinine, corrected serum calcium, serum phosphorus, serum parathyroid hormone, vitamin D use, estimated dry weight, triceps skin-fold thickness, midarm muscle circumference, normalized protein catabolic ratio, appetite assessment, and nutritional supplement use (each specified as per Table 1); two-way interaction terms with sex were included for estimated dry weight, triceps skin-fold thickness, and midarm muscle circumference to account for sex-specific differences in the prognostic significance of these variables. In addition, an expanded model (multivariable + intake) was fit that included all of the above covariates as well as observed caloric and protein intake (each normalized to body weight).
- Figure 5.
Associations between PDP and survival using marginal structural models (MSM) to adjust for age, sex, race, dialysis vintage, access type, eKt/V, diabetes, congestive heart failure, arterial disease, serum albumin, serum creatinine, corrected serum calcium, serum phosphorus, serum parathyroid hormone, vitamin D use, estimated dry weight, triceps skin-fold thickness, midarm muscle circumference, normalized protein catabolic ratio, appetite assessment, nutritional supplement use, and two-way sex-interaction terms for estimated dry weight, triceps skin-fold thickness, and midarm muscle circumference using stabilized inverse probability of treatment and censoring weights. (A) Stratum-specific HRs (95% CIs) with and without additional inclusion of protein and caloric intake; the referent for each model is PDP ≤870 mg/d. (B) HRs (95% CIs) for no phosphate restriction (referent PDP ≤870 mg/d) among predefined subgroups (serum phosphate and vitamin D use categories are based on baseline values); stabilized weights were re-estimated within each group.
Tables
- Table 1.
Baseline comparison of demographic, anthropometric, comorbidity, biochemical, and nutritional characteristics across categories of prescribed dietary phosphate
First Quartile (n = 300)a Second Quartile (n = 314)a Third Quartile (n = 307)a Fourth Quartile (n = 297)a No Phosphate Prescription (n = 533)a Global P Value for Differences among Groupsb PDP (mg/d) 800 (600 to 870) 900 (871 to 999) 1000 (1000 to 1000) 1200 (1001 to 2000) NA NA Age (years) 57.3 ± 14.8 59.1 ± 13.4 58.6 ± 13.5 56.8 ± 13.2 57.2 ± 14.6 0.14 Female genderc 79.7% 57.0% 54.4% 36.4% 55.7% <0.001 Black racec 69.7% 76.4% 65.8% 54.2% 54.6% <0.001 Vintage 0.008 ≤1 year 24.3% 25.8% 22.5% 21.9% 18.6% 1 to 2 years 19% 25.2% 22.2% 27.6% 20.6% 2 to 4 years 23.3% 17.8% 26.1% 25.3% 29.1% >4 years 33.3% 31.2% 29.3% 25.3% 31.7% Accessc <0.001 graft 68.7% 63.7% 65.2% 52.5% 53.9% fistula 23.7% 27.7% 28.7% 41.8% 40.5% catheter 7.7% 8.6% 6.2% 5.7% 5.6% Diabetes 42.7% 47.1% 45.0% 43.1% 45.0% 0.81 Arterial diseasec 53.3% 58.0% 57.7% 58.3% 52.7% 0.34 CHFc 42.7% 40.8% 37.5% 41.4% 35.8% 0.25 EDW (kg) femalec 60.4 ± 12.4 70.6 ± 13.6 68.9 ± 15.2 71.7 ± 15.6 68.0 ± 16.0 <0.001 malec 65.2 ± 12.5 71.2 ± 12.2 73.8 ± 15.4 77.0 ± 13.6 70.5 ± 12.8 <0.001 MAMC (cm) femalec 22.9 ± 3.5 24.3 ± 4.3 24.3 ± 4.0 25.3 ± 4.7 23.6 ± 4.7 0.001 male 24.4 ± 3.3 25.6 ± 2.8 25.6 ± 3.9 26.2 ± 3.4 25.2 ± 4.1 0.02 TSF (mm) femalec 18.7 ± 10.0 22.7 ± 13.4 21.7 ± 10.9 21.7 ± 9.2 23.5 ± 15.2 <0.001 male 12.5 ± 8.5 11.3 ± 6.7 13.8 ± 8.7 14.2 ± 8.3 14.4 ± 11.8 0.004 Alb (g/dl)c 3.59 ± 0.36 3.61 ± 0.37 3.59 ± 0.33 3.65 ± 0.35 3.67 ± 0.36 0.006 Cr (mg/dl)c 9.69 ± 2.84 10.76 ± 3.04 10.44 ± 3.10 10.63 ± 2.80 10.05 ± 2.69 0.001 eKt/V 1.50 ± 0.27 1.49 ± 0.31 1.49 ± 0.31 1.46 ± 0.30 1.49 ± 0.31 0.21 Corrected Ca (mg/dl) 9.62 ± 1.05 9.51 ± 1.02 9.62 ± 0.95 9.52 ± 0.97 9.70 ± 0.89 0.004 (n = 313) Phos (mg/dl) 5.90 ± 1.99 5.73 ± 1.89 5.63 ± 1.82 6.01 ± 1.90 5.72 ± 1.88 0.05 (n = 313) PTH (pg/ml)c <0.001 ≤150 31.3% 30.6% 42.7% 39.4% 44.3% 151 to 300 22.0% 20.4% 20.9% 21.9% 21.6% >300 38.0% 33.4% 27.7% 30.3% 28.0% missing 8.7% 15.6% 8.8% 8.4% 6.2% nPCR (g/kg/d) 1.01 ± 0.25 1.02 ± 0.25 1.05 ± 0.24 1.00 ± 0.27 1.04 ± 0.27 0.004 Vitamin D use 53.7% (n = 298) 54.1% 49.0% (n = 306) 58.3% 55.4% (n = 531) 0.23 Nutritional supplement usec 27.3% 33.1% 25.7% 15.5% 14.6% <0.001 Appetitec 0.004 very good 21.3% 36.0% 26.4% 32.0% 32.3% good 41.0% 32.2% 43.7% 34.7% 37.7% fair 26.0% 21.7% 21.2% 25.6% 22.7% poor 8.3% 8.9% 6.2% 6.4% 6.4% very poor 3.3% 1.3% 2.6% 1.4% 0.9% Observed protein 1.01 ± 0.42 0.93 ± 0.44 0.96 ± 0.40 0.94 ± 0.40 0.92 ± 0.42 0.03 intake (g/kg/d)c (n = 287) (n = 309) (n = 304) (n = 293) (n = 528) Observed caloric intake 24.9 ± 9.7 22.1 ± 9.3 22.6 ± 9.1 23.5 ± 9.8 22.2 ± 9.5 <0.001 (kcal/kg/d)c (n = 287) (n = 309) (n = 304) (n = 293) (n = 528) Observed phosphate 820 ± 380 810 ± 390 840 ± 380 910 ± 430 830 ± 380 0.02 intake (mg/d) (n = 288) (n = 309) (n = 304) (n = 293) (n = 528) The values are expressed as the means ± standard deviation or proportion, except for PDP, which is expressed as median (range). EDW, estimated dry weight; MAMC, midarm muscle circumference; TSF, triceps skin-fold thickness; CHF, congestive heart failure; Alb, serum albumin; Cr, serum creatinine; eKT/V, equilibrated Kt/V; Corrected Ca, corrected serum calcium; Phos, serum phosphate; nPCR, normalized protein catabolic rate; NA, not applicable.
↵a Except where indicated.
↵b P value for global comparisons among groups by Kruskal Wallis and χ2 tests for continuous and categorical variables, respectively.
↵c P < 0.05 for two-way comparison between first quartile and no-prescription groups by Wilcoxon rank sum test.
- Table 2.
Changes in indices of metabolic bone disease control, nutritional status, and body composition in the year after a change in prescribed dietary phosphate
Change over 1 Year after Conversion to More Restrictive PDP (n = 232)a Change over 1 Year after No Change in PDP (n = 1553)a Change over 1 Year after Conversion to More Liberal PDP (n = 236)a P Value for Difference between Groups with Change to More Restrictive versus More Liberal PDP Serum phosphorus (mg/dl) −0.3 ± 1.9 0.1 ± 1.9 0.0 ± 1.9 0.11 Corrected calcium (mg/dl) 0.0 ± 0.9 0.1 ± 1.1 −0.1 ± 1.1 0.22 Serum PTH (pg/ml) 20.4 ± 383 (n = 209) 24.3 ± 362 (n = 1474) 31.0 ± 336 (n = 225) 0.76 Serum albumin (g/dl) −0.1 ± 0.3 0.0 ± 0.3 0.0 ± 0.4 0.11 Serum creatinine (mg/dl) −0.2 ± 2.0 −0.2 ± 1.9 −0.2 ± 1.9 0.85 Normalized PCR (g/kg/d) 0.0 ± 0.3 0.0 ± 0.3 (n = 1554) 0.0 ± 0.2 (n = 235) 0.94 EDW (kg) −0.8 ± 4.5 −0.7 ± 4.6 (n = 1554) −1.3 ± 3.9 (n = 235) 0.24 Triceps skinfold thickness (mm) 0.5 ± 10.8 (n = 216) −0.7 ± 7.7 (n = 1385) −1.0 ± 7.6 (n = 220) 0.11 Mid-arm muscle circumference (cm) −0.5 ± 3.5 (n = 216) 0.0 ± 2.8 (n = 1385) −0.1 ± 3.0 (n = 220) 0.25 Observed caloric intake (kcal/kg/d) 0.3 ± 10.9 (n = 213) 0.0 ± 10.5 (n = 1403) 1.3 ± 10.0 (n = 214) 0.35 Observed protein intake (g/kg/d) 0.0 ± 0.5 (n = 213) 0.0 ± 0.5 (n = 1403) 0.0 ± 0.5 (n = 214) 0.99 PCR, protein catabolic rate; EDW, estimated dry weight.
↵a Except where indicated.
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