Association between ambient carbon monoxide and secondary hyperparathyroidism in nondiabetic patients undergoing peritoneal dialysis

Figures & data

Table 1 Characteristics of the PD patients

Variables	Total patients =141
Age (years)	50±10.4
BSA (m^2)	1.55±0.14
PD duration (months)	67.3±40.4
Sex (male/female)	30/111
Serum Cr (mg/dL)	11.35±2.47
WBC count (×10^9/L)	7.5±2.38
Al (μg/L)	0.8 (0.3–1.3)
iPTH (pg/dL)	166 (71.75–525)
Albumin (g/L)	4.08±0.31
nPNA (g/kg/day)	1.03 (0.88–1.17)
hs-CRP (mg/L)	2.7 (1.14–7.29)
KT/Vurea T	2.26±0.33
CCrn T (L/week/1.73 m^2)	59.25±11.13
Dialysate Ca (2.5/3.5 mEq/L), n	60/81
Use of calcium-based phosphate binders, n	131
Use of aluminum-based phosphate binders, n	11
Use of calcitriol, n	51
Environmental PM10 (μg/m^3)	49.1 (44.9–56.2)
Environmental PM2.5 (μg/m^3)	29.69 (26.44–29.88)
Environmental SO2 (ppb)	4.4 (3.9–5.85)
Environmental NO2 (ppb)	20.1 (16.4–22.3)
Environmental CO (ppm)	0.53 (0.44–0.57)
Environmental O3 (ppb)	28.7 (27.6–30.85)

Note: Data presented as mean ± SD or median (IQR), unless otherwise specified.

Abbreviations: BSA, body-surface areas; PD, peritoneal dialysis; Cr, creatinine; WBC, white blood cell; Al, aluminum; iPTH, intact parathyroid hormone; nPNA, normalized protein nitrogen appearance; hs-CRP, high-sensitivity C-reactive protein; KT/V_urea T, peritoneal KT/V_urea + renal KT/V_urea; CCrn T, total Cr clearance; PM₁₀, particulate matter with aerodynamic diameter less than 10 μm; PM_2.5, particulate matter with aerodynamic diameter less than 2.5 μm; SD, standard deviation; IQR, interquartile range.

Table 2 Comparison of patients with iPTH ≥180 pg/dL and without iPTH <180 pg/dL hyperparathyroidism

Variables	iPTH <180 pg/dL (n=73)	iPTH ≥180 pg/dL (n=68)	P-value
Age (years)	51.06±11.07	48.94±9.73	0.22
PD duration (months)	60.19±39.07	75.11±40.72	0.02
Residual renal function (mL/min)	3.33 (0–10.7)	0.39 (0–5.18)	0.02
Sex, male/female (n)	16/57	14/54	0.99
BUN (mg/dL)	60.54±15.25	58.06±16.96	0.36
Serum Cr (mg/dL)	11.36±2.59	11.35±2.35	0.99
WBC count (×10^9/L)	7.62±2.49	7.37±2.25	0.53
Al (μg/L)	0.8 (0.25–1.3)	0.8 (0.4–1.45)	0.6
Hypoalbuminemia, n	9/73 (12.3%)	18/68 (26.5%)	0.05
nPNA (g/kg/day)	1.04±0.2	1.04±0.22	0.86
Ca (mg/dL)	10.24±0.86	10.21±0.87	0.82
Phosphate (mg/dL)	4.8±1.09	5.23±1.29	0.03
Dialysate Ca (2.5/3.5 mEq/L)	30/43	30/38	0.736
hs-CRP (mg/L)	2.17 (1.11–5.96)	3 (1.27–9.13)	0.35
KT/Vurea T	2.23±0.34	2.29±0.33	0.25
CCrn T (L/week/1.73 m^2)	58.56±11.47	59.98±10.79	0.45
Environmental SO2 (ppb)	4.4 (3.9–5.9)	5.2 (4.0–5.75)	0.39
Environmental NO2 (ppb)	20.1 (16.3–21.0)	21.0 (18.02–22.9)	0.02
Environmental CO (ppm)	0.53 (0.4–0.57)	0.57 (0.44–0.66)	0.01
Environmental O3 (ppb)	29.0 (28.2–31.2)	28.7 (26.4–29.22)	0.06
Environmental PM10 (μg/m^3)	49.4 (44.9–56.2)	48 (44.9–58.45)	0.8
Environmental PM2.5 (μg/m^3)	29.69 (26.44–29.88)	27.56 (26.51–29.85)	0.35

Notes: Data are expressed as median (interquartile range) in nonnormal distribution variables, and as means ± standard deviation in normal distribu tion variables, unless otherwise specified.

Abbreviations: iPTH, intact parathyroid hormone; PD, peritoneal dialysis; BUN, blood urea nitrogen; Cr, creatinine; WBC, white blood cell; Al, aluminum; nPNA, normalized protein nitrogen appearance; hs-CRP, high-sensitivity C-reactive protein; KT/V_urea T, peritoneal KT/V_urea + renal KT/V_urea; CCrn T, total Cr clearance; PM₁₀, particulate matter with aerodynamic diameter less than 10 μm; PM_2.5, particulate matter with aerodynamic diameter less than 2.5 μm.

Table 3 Logistic regression analysis between hyperparathyroidism (iPTH $180 pg/dL) and clinical variables (n=141)

Variables	Hyperparathyroidism (iPTH ≥180 pg/dL)
	Univariate logistic regression, OR (95% CI)	P-value	Forward multivariate logistic regression, OR (95% CI)	P-value
High SO2 (ppb) exposure	1.44 (0.74–2.8)	0.27
High NO2 (ppb) exposure	2.3 (1.16–4.57)	0.01
High CO (ppm) exposure	2.43 (1.23–4.82)	0.01	3.22 (1.42–7.28)	0.005
High O3 (ppb) exposure	0.77 (0.39–1.49)	0.44
High PM10 exposure	0.578 (0.296–1.126)	0.10
High PM2.5 exposure	0.726 (0.36–1.44)	0.36
Age (years)	0.98 (0.94–1.01)	0.22
Male sex	0.92 (0.41–2.07)	0.84
Serum Cr (mg/dL)	0.99 (0.87–1.14)	0.99
CCrn T (L/week/1.73 m^2)	1.01 (0.98–1.04)	0.44
Log nPNA (g/kg/day)	1.14 (0.25–5.1)	0.86
Hypoalbuminemia	2.56 (1.06–6.18)	0.03	3.76 (1.29–10.94)	0.015
Ca (mg/dL)	0.95 (0.65–1.40)	0.82
Phosphate (mg/dL)	1.36 (1.02–1.82)	0.03	1.66 (1.17–2.37)	0.005
Log hs-CRP (mg/dL)	1.34 (0.72–2.5)	0.35
PD duration (months)	1.01 (1.001–1.018)	0.03
Use of calcitriol	6.83 (3.12–14.96)	<0.001	8.25 (3.43–19.85)	<0.001
Use of calcium-based phosphate binders	1.43 (0.38–5.31)	0.59
Use of aluminum-based phosphate binders	12.41 (1.54–99.81)	0.01
Anuria	2.15 (1.11–4.34)	0.02
CAD	0.53 (0.047–5.98)	0.60
HTN	0.79 (0.4–1.55)	0.5
High education level	1.16 (0.59–2.25)	0.65
Log Al (μg/L)	1.23 (0.6–2.52)	0.56
Dialysate Ca (mEq/L)	0.88 (0.45–1.72)	0.717

Notes: High SO₂ exposure represented as ≥ mean value of 4.4 ppb; high NO₂ exposure represented as ≥ mean value of 20.1 ppb; high CO exposure represented as ≥ mean value of 0.53 ppm; high O₃ exposure represented as ≥ mean value of 28.7 ppb; high PM₁₀ exposure represented as ≥ median value of 49.1 μg/m³; high PM_2.5 exposure represented as ≥ median value of 29.69 μg/m³; anuria defined as 24-hour urine volume <50 cm³.

Abbreviations: iPTH, intact parathyroid hormone; PM₁₀, particulate matter with aerodynamic diameter less than 10 μm; PM_2.5, particulate matter with aerodynamic diameter less than 2.5 μm; Cr, creatinine; CCrn T, total Cr clearance; nPNA, normalized protein nitrogen appearance; hs-CRP, high-sensitivity C-reactive protein; PD, peritoneal dialysis; CAD, coronary arterial disease; HTN, hypertension.

Figure 1 Comparison of patients living in high and low CO-exposure areas.

Notes: Patients living in high CO-exposure areas had higher iPTH levels than patients living in low CO-exposure areas. High and low CO exposures were separated by a mean value of 0.53 ppm. iPTH, nPNA and hs-CRP are represented as median values, and the others are represented as mean values. *P<0.05.
Abbreviations: iPTH, intact parathyroid hormone; nPNA, normalized protein nitrogen appearance; P, phosphate; hs-CRP, high-sensitivity C-reactive protein; CCrn T, total creatinine clearance; KT/V_urea T, peritoneal KT/V_urea + renal KT/V_urea; WBC, white blood cell; Hb, hemoglobin.

Figure 2 Inference of the correlation between air pollution, CO, and parathyroid hormone.

Abbreviations: ↓, decrease; ↑, increase; PD, peritoneal dialysis.