Risk factors and clinical prediction models for osteoporosis in pre-dialysis chronic kidney disease patients

Figures & data

Table 1. Baseline characteristics of patients.

Characteristics	Total (N = 326)	Non osteoporosis (N = 255)	Osteoporosis (N = 71)	p value
Age (years)	64 ± 15	62 ± 15	73 ± 11	<0.001
BMI (kg/m^2)	24.39 ± 5.63	24.88 ± 5.83	22.29 ± 4.11	0.002
Hypertension (n, %)	255 (78.2)	200 (78.4)	55 (77.4)	0.499
Diabetes Mellitus (n, %)	166 (50.9)	132 (51.7)	34 (47.8)	0.399
Laboratory results
UREA (mmol/L)	13.24 (8.31,20.75)	12.85 (8.23, 20.83)	15.56 (9.08, 20.72)	0.283
CREA (umol/L)	230 (116,468)	211 (116, 469)	268 (116, 464)	0.657
URIC (umol/L)	446.32 ± 136.91	452.16 ± 135.53	425.15 ± 140.78	0.144
Cys-C (mg/L)	2.51 (1.66,3.70)	2.44 (1.62, 3.61)	2.79 (1.97, 3.98)	0.050
Ca (mmol/L)	2.15 (2.02,2.26)	2.15 (2.02, 2.26)	2.15 (2.02, 2.25)	0.970
P (mmol/L)	1.28 (1.13,1.57)	1.28(1.13, 1.55)	1.28 (1.16, 1.60)	0.601
Mg (mmol/L)	0.90 (0.82,0.98)	0.90 (0.82, 0.98)	0.89 (0.82, 1.00)	0.718
Fe (umol/L)	9.75 (6.90,13.53)	10.00 (7.05, 13.80)	9.60 (6.30, 13.10)	0.314
TRF (g/L)	1.92 ± 0.44	1.92 ± 0.44	1.92 ± 0.42	0.945
ALT (U/L)	18 (12,26)	18 (13, 27)	15 (12, 20)	0.023
AST (U/L)	20 (16,26)	20 (16, 26)	20 (16, 24)	0.774
ALP (U/L)	85 (66,103)	82 (65, 101)	89 (71, 127)	0.016
ALB(g/L)	37.2 (32.55,41.00)	37.40 (32.60, 41.10)	36.80 (31.80, 40.68)	0.649
TCHOL (mmol/L)	4.98 ± 1.70	5.10 ± 1.72	4.55 ± 1.55	0.016
TG (mmol/L)	1.56 (1.03,2.31)	1.64 (1.10, 2.37)	1.22 (0.81, 2.06)	0.004
eGFR (mL/min/1.73m^2)	22.62 (9.32,47.22)	24.53 (9.33, 48.59)	16.44 (8.67, 38.76)	0.085
NBAP (ug/L)	11.03 (8.35,13.99)	10.82 (8.32, 13.69)	12.46 (8.36, 17.45)	0.108
25-(OH)-Vitamin D (ng/ml)	18.70 (13.45,24.75)	19.05 (13.30, 26.25)	18.20 (14.10, 22.95)	0.542
PTH (pg/ml)	66.48 (36.76,175.36)	62.28 (36.47, 165.25)	94.17 (38.18, 203.14)	0.307
HGB (g/L)	106.88 ± 24.24	108.92 ± 24.00	99.24 ± 23.79	0.003
WBC (*10^9/L)	7.13 (5.82,9.00)	7.16 (5.89, 9.14)	6.91 (5.55, 8.81)	0.359
NEU (*10^9/L)	4.80 (3.79,6.55)	4.82 (3.87, 6.62)	4.80 (3.53, 6.48)	0.576
LYM (*10^9/L)	1.48 ± 0.62	1.52 ± 0.64	1.33 ± 0.50	0.010
PLT (*10^9/L)	234.58 ± 82.38	237.68 ± 80.72	222.96 ± 87.99	0.191
D-dimer (ng /ml)	895 (390,1710)	730 (347, 1520)	1205 (793, 1295)	0.001
Dual-energy X-ray Absorptiometry
Whole body bone BMD (g/cm^3)	1.06 ± 0.14	1.09 ± 0.12	0.93 ± 0.14	<0.001
Whole body bone T	−0.30 ± 1.13	0.06 ± 0.94	−1.24 ± 1.06	<0.001
Whole body bone Z	0.30 (-0.40, 0.70)	0.30 (-0.40, 0.70)	–	–
BMD of L1-L4 (g/cm^3)	1.06 ± 0.19	1.11 ± 0.17	0.85 ± 0.12	<0.001
L1-L4 T	−0.45 ± 1.67	0.07 ± 1.47	−2.14 ± 1.01	<0.001
L1-L4 Z	0.70 (-0.25, 1.30)	0.70 (-0.10, 1.30)	–	–
BMD of Femoral (g/cm^3)	0.78 ± 0.15	0.81 ± 0.12	0.56 ± 0.08	<0.001
Femoral T	−1.70 ± 1.19	−1.24 ± 0.95	−3.09 ± 0.66	<0.001
Femoral Z	−0.60 (-1.10, 0.13)	−0.50 (-1.10, 0.15)	–	–

Data were presented as mean ± SD, %, or median (interquartile range). BMI, body index mass; CREA, creatinine; URIC, uric acid; Cys-C, cystatin c; Ca, serum calcium; P, serum phosphorus; Mg, serum magnesium; Fe, serum iron; TRF, transferrin; ALT, glutamic-pyruvic transaminase; AST, glutamic oxaloacetic transaminase; ALP, alkaline phosphatase; ALB, serum albumin; TCHOL, total cholesterol; TG, triglyceride; eGFR, glomerular filtration rate; NBAP, Serum bone alkaline phosphatase; iPTH, intact parathyroid hormone; HGB, hemoglobin; WBC, white blood-cell; NEU, absolute value of neutrophil cell; LYM, absolute value of lymphocytes; PLT, platelet.

Table 2. Binary logistic regression analysis of the correlation between relevant indicators and osteoporosis in pre-dialysis patients of different genders.

Study objects	variable	β value	p value	OR	95%CI
Male	Age	0.10	0.04	1.11	(1.00,1.23)
	25-(OH)-vitamin D	−0.2	0.04	0.83	(0.69,0.99)
Female	Age	0.17	0.01	1.18	(1.05,1.33)
	Underweight	3.60	0.04	36.40	(1.15,1151.54)
	iPTH	−0.02	0.03	0.98	(0.96,1.00)
	NBAP	0.36	0.01	1.44	(1.10,1.89)
	G5	2.40	0.03	11.04	(1.27,96.35)

iPTH, intact parathyroid hormone; NBAP, Serum bone alkaline phosphatase. BMI was categorized into three distinct classes: underweight (<18.5 kg/m²), normal weight (18.5 kg/m²≤BMI < 24.0 kg/m²), and overweight or obese (BMI ≥24 kg/m²). Renal function was stratified based on eGFR into two grades: G1-G4 (eGFR ≥ 15 mL/min/1.73m²) and G5 (eGFR < 15 mL/min/1.73m²). The covariates considered in the male and female subgroups were as follows: Sex, BMI, Ca, P, 25(OH)D, eGFR staging, iPTH, and NBAP, respectively.

Figure 1. The ROC curves and nomogram of predictive models for osteoporosis in patients of different genders. (A, B) The ROC curves and nomogram for male pre-dialysis patients. (C, D) The ROC curves and nomogram for female pre-dialysis patients. In the line corresponding to BMI, the number 1 represents normal weight (18.5 kg/m²≤BMI < 24.0 kg/m²), the number 2 represents underweight (BMI < 18.5 kg/m²), the number 3 represents overweight or obese (BMI ≥24 kg/m²). In the line segment corresponding to the stage of renal function, the number 1 represents the early stage of CKD (G1-G4), the number 2 represents the late stage of CKD (G5).

Figure 2. The ROC curves and nomograms of predictive models for osteoporosis in patients with different renal function stages. (A, B) The ROC curves and nomograms for G1-G4 patients. In the line corresponding to BMI, the number 1 represents normal weight (18.5 kg/m²≤BMI < 24.0 kg/m²), the number 2 represents underweight (BMI < 18.5 kg/m²), the number 3 represents overweight or obese (BMI ≥24 kg/m²). (C, D) The ROC curves and nomograms for G5 patients.

Table 3. Binary logistic regression analysis on the correlation between related indicators and osteoporosis in pre-dialysis patients with different renal function stages.

Study objects	variable	β value	p value	OR	95%CI
G1-G4	Age	0.07	0.02	1.07	(1.01,1.13)
	NBAP	0.13	0.02	1.14	(1.02,1.28)
	Underweight	2.39	0.03	10.88	(1.28,92.46)
G5	Age	0.13	0.004	1.14	(1.04,1.24)
	25-(OH)-vitamin D	−0.16	0.05	0.85	(0.73,1.00)
	iPTH	−0.01	0.04	0.99	(0.97,1.00)
	NBAP	0.277	0.017	1.32	(1.05,1.65)

NBAP, Serum bone alkaline phosphatase; iPTH, intact parathyroid hormone. BMI was categorized into three distinct classes: underweight (<18.5 kg/m²), normal weight (18.5 kg/m²≤BMI < 24.0 kg/m²), and overweight or obese (BMI ≥24 kg/m²). The covariates included were Age, Sex, BMI, Ca, P, 25-(OH)-vitamin D, iPTH, and NBAP.