Blood lead level: an overlooked risk of carpal tunnel syndrome in hemodialysis patients

Figures & data

Table 1. Baseline characteristics of 866 MHD patients.

Characteristics	Total (n = 866) Mean ± SD/ Median (interquartile range)	Normal range in CGMH
Demographics
Age (y)	56.18 ± 13.59
Male, n (%)	440 (50.8%)
Body mass index (kg/m^2)	22.19 ± 3.18
Smoking, n (%)	150 (17.3%)
Co-morbidity
Diabetes mellitus, n (%)	192 (22.2%)
Hypertension, n (%)	339 (39.1%)
Previous CVD, n (%)	41 (4.7%)
HBV, n (%)	98 (11.3%)
HCV, n (%)	168 (19.4%)
CTS, n (%)	76 (8.8%)
Dialysis Related Data
Hemodialysis duration (y)	6.96 ± 5.35
Erythropoietin (U/kg/week)	73.62 ± 47.37
Fistula as blood access, n (%)	689 (79.6%)
Hemodiafiltration, n (%)	187 (21.6%)
Kt/Vurea (Daugirdes)	1.79 ± 0.32
nPCR (g/kg/day)	1.18 ± 0.26
Residual daily urine of >100 mL, n (%)	178 (20.6%)
Biochemical Data
Hemoglobin (g/dL)	10.51 ± 1.36	M: 13.5–17.5 F: 12–16
Albumin (g/dL)	4.06 ± 0.34	3.5–5.5
Creatinine (mg/dL)	10.88 ± 2.39	M: 0.64–1.27 F: 0.44–1.03
Ferritin (μg/L)^a	305.0 (129.57, 504.45)	M: 22–322 F: 10–291
Corrected-calcium (mg/dL)	9.94 ± 0.93	7.9–9.9
Phosphate (mg/dL)	4.84 ± 1.35	2.4–4.7
Intact parathyroid hormone (pg/mL)^a	130.1 (52.52, 319.2)	ESRD: 168–342
hsCRP (mg/L)^a	2.95 (1.4, 7.01)	<5
hsCRP > 3 mg/L, n (%)	420 (48.5%)
Cardiovascular Risks
Cholesterol (mg/dL)	171.3 ± 37.66	<200
Triglyceride (mg/dL)	164.33 ± 115.8	<150
LDL (mg/dL)	94.83 ± 30.59	<100
BLL (ug/dL)^a	10.39 (7.26, 14.19)	<10

M: male; F: female; ESRD: end stage renal disease; MHD: maintenance hemodialysis; CTS: carpal tunnel syndrome; CVD: cardiovascular disease; HBV: hepatitis B virus infection; HCV: hepatitis C virus infection; nPCR: normalized protein catabolic rate; hsCRP: high-sensitivity C-reactive protein; LDL: low density lipoprotein; Kt/V_urea (Daugirdes): dialysis clearance of urea; BLL: blood lead level; CGMH: Chang Gung Memorial Hospital.

^a Non-normal distribution data are presented as median (interquartile range).

Table 2. Comparison of the baseline characteristics between different BLLs.

	Low-normal BLL (n = 408)	High-normal BLL (n = 380)	High BLL (n = 78)	p Value
Age (y)	56.21 ± 13.89	55.87 ± 13.26	57.52 ± 13.66	.72
Male, n (%)	48.3	52.1	57.7	.09
Body mass index (kg/m^2)	22.21 ± 3.27	22.22 ± 3.13	21.94 ± 3.01	.64
Smoking, n (%)	15.7	18.2	21.8	.15
Diabetes mellitus, n (%)	27.5	19.2	9.0	<.001
Hypertension, n (%)	39.0	39.2	39.7	.89
Previous CVD, n (%)	4.2	6.1	1.3	.92
HBV, n (%)	10.0	12.1	14.1	.22
HCV, n (%)	14.7	22.1	30.8	<.001
CTS, n (%)	2.2	11.6	29.5	<.001
Hemodialysis duration (y)	5.73 ± 4.75	7.58 ± 5.39	10.28 ± 6.18	<.001
Erythropoietin (U/kg/week)	79.58 ± 46.34	69.57 ± 47.73	62.27 ± 47.33	<.001
Fistula as blood access, n (%)	78.7	79.7	83.3	.39
Hemodiafiltration, n (%)	15.0	24.7	41	<.001
Kt/Vurea (Daugirdes)	1.75 ± 0.30	1.82 ± 0.32	1.90 ± 0.39	<.001
nPCR (g/kg/day)	1.18 ± 0.26	1.19 ± 0.27	1.16 ± 0.27	.97
Residual daily urine of >100 mL, n (%)	23.5	18.4	15.4	.035
Hemoglobin (g/dL)	10.33 ± 1.31	10.63 ± 1.34	10.88 ± 1.57	<.001
Albumin (g/dL)	4.08 ± 0.33	4.05 ± 0.35	3.98 ± 0.36	.018
Creatinine (mg/dL)	10.88 ± 2.46	10.90 ± 2.29	10.79 ± 2.47	.88
Corrected-calcium (mg/dL)	9.89 ± 0.90	9.96 ± 0.94	10.06 ± 0.99	.11
Phosphate (mg/dL)	4.83 ± 1.35	4.87 ± 1.37	4.72 ± 1.26	.76
Ferritin (μg/L)^a	359.9 (165.1,569.85)	272.4 (111.25,445.55)	283.55 (156.32,420.45)	.001
Intact parathyroid hormone (pg/mL)^a	112.4 (41.5,249.1)	144.25 (55.6,365.42)	195.85 (82.67,435.27)	<.001
hsCRP (mg/L)^a	2.87 (1.34,7.51)	2.98 (1.54,6.49)	3.36 (1.4,7.38)	.6
LDL (mg/dL)	93.95 ± 30.63	95.94 ± 30.57	93.90 ± 30.69	.62

Low-normal BLL, BLL <10 μg/dL (reference).

High-normal BLL, 20 μg/dL > BLL ≥10 μg/dL.

High BLL, BLL ≥20 μg/dL.

BLL: blood lead level; MHD: maintenance hemodialysis; CTS: carpal tunnel syndrome; CVD: cardiovascular disease; HBV: hepatitis B virus infection; HCV: hepatitis C virus infection; nPCR: normalized protein catabolic rate; hsCRP: high-sensitivity C-reactive protein; LDL: low density lipoprotein; Kt/V_urea (Daugirdes): dialysis clearance of urea.

^a Non-normal distribution data are presented as median (interquartile range).

Table 3. Univariate logistic regression analysis of predictors of CTS in MHD Patients.

Variables	Odds ratio (OR) 95% confidence Intervals (CI)	p
Age (years)	1.007 (0.99, 1.025)	.432
Male	0.812 (0.5, 1.30)	.386
Body mass index (kg/m^2)	0.96 (0.89, 1.03)	.33
Smoking	0.7 (0.35, 1.4)	.31
Diabetes mellitus	0.33 (0.15, 0.73)	.007
Hypertension	0.95 (0.58, 1.55)	.85
Previous CVD	0.52 (0.12, 2.19)	.37
HBV	0.65 (0.27, 1.53)	.32
HCV	2.07 (1.23, 3.47)	.006
Hemodialysis duration (years)	1.17 (1.13, 1.22)	<.001
Fistula as blood access	1.76 (0.89, 3.51)	.1
Hemodiafiltration	1.54 (0.91, 2.6)	.11
Kt/Vurea (Daugirdes)	3.39 (1.71, 6.7)	<.001
nPCR (g/kg/day)	3.17 (1.35, 7.4)	.008
Non-Anuria	0.3 (0.13, 0.72)	.007
Hemoglobin (g/dL)	1.21 (1.02, 1.43)	.027
Albumin < 4 g/dL	2.038 (1.26, 3.27)	.003
Albumin	0.489 (0.253, 0.946)	.034
Creatinine (mg/dL)	0.94 (0.85, 1.04)	.3
Corrected-calcium (mg/dL)	1.18 (0.92, 1.51)	.18
Phosphate (mg/dL)	0.95 (0.79, 1.13)	.57
Log ferritin	1.07 (0.65, 1.78)	.76
Log iPTH	2.62 (1.63, 4.22)	<.001
hsCRP >3.0 mg/L	1.18 (0.73, 1.90)	.48
Cholesterol (mg/dL)	1.002 (0.99, 1.008)	.63
Triglyceride (mg/dL)	1.00 (0.99, 1.002)	.73
Log BLL	118.67 (31.72, 443.92)	<.001
BLLs		<.001
Low-normal BLL, BLL < 10 ug/dL (reference)
High-normal BLL, 20 ug/dL > BLL ≥ 10 ug/dL	5.806 (2.79, 12.06)	<.001
High BLL, BLL ≥ 20 ug/dL	18.539 (8.16, 42.11)	<.001
Mean previous 12-month Environmental PM2.5 (ug/m^3)	1.078 (1.008, 1.153)	.027

CTS: carpal tunnel syndrome; MHD: maintenance hemodialysis; CVD: cardiovascular disease; HBV: hepatitis B virus infection; HCV: hepatitis C virus infection; nPCR: normalized protein catabolic rate; hsCRP: high-sensitivity C-reactive protein; LDL: low density lipoprotein; Kt/V_urea (Daugirdes): dialysis clearance of urea; iPTH: intact parathyroid hormone; Pb: blood lead; BLL: blood lead level; PM_2.5: particulate matter with an aerodynamic diameter of <2.5 mm.

Table 4. Analysis A: Multivariate logistic regression analysis of predictors of CTS in MHD Patients with log Pb.

Variables	Odds ratio (OR) 95% confidence Intervals (CI)	p
Diabetes mellitus	0.983 (0.931–1.034)	NS
HCV	1.482 (0.911, 2.192)	NS
Hemodialysis duration (years)	1.195 (1.131,1.264)	<.001
Kt/Vurea (Daugirdes)	2.874 (0.951–4.692)	NS
nPCR (g/kg/day)	3.743 (1.478,9.482)	.005
Non-Anuria	0.453 (1.035–0.722)	NS
Hemoglobin (g/dL)	1.070 (0.953–1.211)	NS
Albumin < 4 g/dL	2.102 (1.220,3.621)	.007
Log iPTH	1.514 (0.955–2.026)	NS
Log BLL	54.810 (13.622,220.54)	<.001
Mean previous 12-month Environmental PM2.5 (ug/m^3)	1.073 (0.999,1.152)	NS

CTS: carpal tunnel syndrome; MHD: maintenance hemodialysis; nPCR: normalized protein catabolic rate; hsCRP: high-sensitivity C-reactive protein; Kt/V_urea (Daugirdes): dialysis clearance of urea; iPTH: intact parathyroid hormone; BLL: blood lead level; PM_2.5: particulate matter with an aerodynamic diameter of <2.5 mm.

Table 5. Analysis B: Multivariate logistic regression analysis of predictors of CTS in MHD Patients with BLL category.

Variables	Odds ratio (OR) 95% confidence Intervals (CI)	p
Diabetes mellitus	0.972 (0.946–1.041)	NS
HCV	1.373 (0.925, 1.996)	NS
Hemodialysis duration (years)	1.197 (1.132, 1.265)	<.001
Kt/Vurea (Daugirdes)	2.913 (0.934–4.731)	NS
nPCR (g/kg/day)	3.862 (1.530, 9.751)	.004
Non-Anuria	0.452 (1.034–0.731)	NS
Hemoglobin (g/dL)	1.075 (0.964–1.221)	NS
Albumin < 4 g/dL	2.187 (1.269, 3.768)	.005
Log iPTH	1.512 (0.957–2.028)	NS
BLLs		<.001
Low-normal BLL, BLL <10 μg/dL (reference)
High-normal BLL, 20 μg/dL > BLL ≥10 μg/dL	4.839 (2.262, 10.351)	<.001
High BLL, BLL ≥20 μg/dL	12.952 (5.391, 31.119)	<.001
Mean previous 12-month Environmental PM2.5 (ug/m^3)	1.075 (0.996, 1.159)	NS

CTS: carpal tunnel syndrome; HCV: hepatitis C virus infection; MHD: maintenance hemodialysis; nPCR: normalized protein catabolic rate; Kt/V_urea (Daugirdes): dialysis clearance of urea; iPTH: intact parathyroid hormone; BLL: blood lead level; PM_2.5: particulate matter with an aerodynamic diameter of <2.5 mm.

Table 6. Analysis C: Multivariate logistic regression analysis of predictors of CTS in MHD Patients with Pb ≥12.3 μg/dL.

Variables	Odds ratio (OR) 95% confidence intervals (CI)	p
Diabetes mellitus	0.991 (0.955–1.031)	NS
HCV	1.378 (0.929, 1.987)	NS
Hemodialysis duration (years)	1.203 (1.138, 1.273)	<.001
Kt/Vurea (Daugirdes)	2.918 (0.938–4.742)	NS
nPCR (g/kg/day)	3.207 (1.273, 8.078)	.013
Non-Anuria	0.460 (1.040–0.742)	NS
Hemoglobin (g/dL)	1.077 (0.975–1.223)	NS
Albumin <4 g/dL	2.221 (1.284, 3.842)	.004
Log iPTH	1.521 (0.957–2.036)	NS
BLL ≥12.3 μg/dL	6.827 (3.737, 12.472)	<.001
Mean previous 12-month Environmental PM2.5 (ug/m^3)	1.009 (0.999, 1.020)	NS

CTS: carpal tunnel syndrome; HCV: hepatitis C virus infection; MHD: maintenance hemodialysis; nPCR: normalized protein catabolic rate; Kt/V_urea (Daugirdes): dialysis clearance of urea; iPTH: intact parathyroid hormone; BLL: blood lead level; PM_2.5: particulate matter with an aerodynamic diameter of <2.5 mm.