The role of a parental history of Balkan endemic nephropathy in the occurrence of BEN: a prospective study

Figures & data

Figure 1 Hypothesized path diagram.

Note: Arrows represent the effect of one variable on another.
Abbreviation: BEN, Balkan endemic nephropathy.

Table 1 Characteristics of participants stratified by incidence of BEN in year 2005–2006

Variables	Definite BEN (n = 15) N cases (%)	Probable BEN (n = 23) N cases (%)	No BEN (n = 162) N cases (%)
Sex
Female	8 (53.33)	14 (60.87)	84 (51.85)
Parental history of BEN
Biparental	5 (33.33)	8 (34.78)	21 (12.96)
Mother	8 (53.33)	6 (26.09)	26 (16.05)
Father	2 (13.33)	9 (39.13)	23 (14.20)
Living in endemic area
<20 years	0 (0.00)	2 (8.70)	22 (13.58)
21–40 years	3 (20.00)	3 (13.04)	64 (39.51)
≥41 years	12 (80.00)	18 (78.86)	76 (46.91)
Body mass index
Overweight	11 (73.33)	10 (43.48)	69 (42.59)
Obesity	2 (13.33)	9 (39.13)	42 (25.93)
History of other kidney disease
Pyelonephritis	3 (20.00)	2 (8.70)	8 (4.97)
Other (stone, cystitis, cancer)	3 (20.00)	4 (17.39)	22 (13.66)
Smoking status
Current	4 (26.67)	4 (17.39)	60 (37.64)
Exsmoker	1 (6.67)	0 (0.00)	4 (2.47)
Mean (95% CI, or 5%, 95%)
Age (year)	61.26 (56.79, 65.74)	54.78 (51.46, 58.11)	49.69 (48.26, 51.10)
Kidney length (mm)	109.88 (102.64, 117.02)	113.20 (109.74, 116.64)	119.03 (117.94, 120.13)
Kidney cortex width (mm)	12.99 (11.72, 14.25)	14.65 (13.81, 16.65)	16.07 (15.79, 16.35)
CCr (mL/min/1.73 m^2)	73.23 (62.68, 81.78)	83.67 (78.80, 88.65)	91.03 (88.42, 93.65)
CRPa (mg/dL)	0.50 (0.08, 3.43)	0.44 (0.09, 1.71)	0.27 (0.06, 1.73)
β2Ma (μg/g creatinine)	123.56 (75.77, 892.29)	114.89 (38.72, 800.00)	108.02 (47.84, 363.28)

Note:

a Median.

Abbreviations: CCr, creatinine clearance rate; BEN, Balkan endemic nephropathy; β₂M, β₂-microglobulin; CRP, C-reactive protein.

Table 2 Rank correlation coefficients (Spearman) of parental history, age, and clinical markers

	n = 219					n = 198	n = 219
	Age (years)	Kidney cortex width	Kidney length	CCr	β2M	CRP	Biparental	Mother	Father
Age (year)	1.00
Kidney cortex width	−0.421*	1.00
Kidney length	−0.192*	0.363*	1.00
CCr	−0.641*	0.458*	0.294*	1.00
β2M	0.281*	−0.273*	0.003	−0.212*	1.00
CRP	0.236*	−0.146*	−0.015	−0.113	0.071	1.00
Biparental	0.183*	−0.067	−0.084	−0.040	−0.045	0.179*	1.00
Mother	0.133*	−0.047	−0.176*	−0.093	0.072	0.131	−0.237*	1.00
Father	−0.181*	−0.066	−0.012	0.051	−0.029	−0.038	−0.127*	−0.237*	1.00

Note:

* P value < 0.05.

Abbreviations: CCr, creatinine clearance rate; BEN, Balkan endemic nephropathy; β₂M, β₂-microglobulin; CRP, C-reactive protein.

Figure 2 Direct and indirect path linking parental Balkan endemic nephropathy (BEN) and the incidence of BEN.

Notes: The unstandardized (standard error) parameter estimates are shown. The dotted line presents a significant statistic (P < 0.05) of an indirect association between parental history of BEN and the occurrence of BEN. The solid line shows a statistically significant direct effect between parental history of BEN and the occurrence of BEN (P < 0.05). The underlined coefficients are logit coefficients and need to be exponentiated to calculate odds ratios. The nonunderlined coefficients are interpreted as linear regression coefficients: per unit of increase in the independent variable there will be a coefficient unit of increase in the dependent variable. The curved line with arrows at each end indicates a correlation between variables.

Figure 3 Direct and indirect path linking a specific status of parental Balkan endemic nephropathy (BEN) and the incidence of BEN.

Notes: The unstandardized (standard error) parameter estimates are shown. The dotted line presents a significant statistic (P < 0.05) of an indirect association between parental history of BEN and the occurrence of BEN. The solid line shows a statistically significant direct effect between parental history of BEN and the occurrence of BEN (P < 0.05). The underlined coefficients are logit coefficients and need to be exponentiated to estimate odds ratios. The nonunderlined coefficients are interpreted as linear regression coefficients: per unit of increase in the independent variable there will be a coefficient unit of increase in the dependent variable. The curved line with arrows at each end indicates a correlation between variables.