Health economic evaluation of peritoneal dialysis based on cost-effectiveness in Japan: a preliminary study

Figures & data

Figure 1 Method of determining the equivalence of CAPD and APD groups. To compare the cost-effectiveness of CAPD and APD, data were processed by conducting an analysis of the propensity score and a stratified analysis to ensure equivalence between the two groups.

Table 1 Patients’ clinical characteristics

Characteristic	PD (Mean±Standard deviation)	HD (Mean±Standard deviation)	Significant difference (p-value)
Number of cases (cases)	179	25	—
Age (years)	64.6±13.2	62.8±14.0	n. s.
Males (%)	53.0	36.0	n. s.
Duration of dialysis (months)	35.0±14.4	36.1±11.6	n. s.
Primary disease (cases, %)
Diabetic nephropathy	76; 42.5%	5; 25.0%	n. s.
Glomerulonephritis	50; 30.0%	11; 45.8%	n. s.
Nephrosclerosis	21; 11.7%	2; 8.3%	n. s.
Other	32;17.9%	6; 20.8%	n. s.
Laboratory tests
Residual Kt/V	0.7±0.3	—	—
BUN (mg/dL)	50.7±13.7	69.6 ±14.3	**
Alb (g/dL)	3.2±0.5	3.9±0.3	**
P (mg/dL)	4.7±1.2	5.3±1.1	n. s.
K (mEq/L)	4.1±0.6	4.9±0.5	**
Hb (g/dL)	10.7±1.2	10.2±0.8	n. s.
HDL (mg/dL)	55.1±23.6	62.6±17.2	n. s.
TG (mg/dL)	133.4±83.6	123.1±73.4	n. s.
Type of PD
CAPD (cases, %)	144; 80.4%
APD (cases, %)	35; 19.5%

Notes: Welch’s t-test **p < 0.01, n. s.: not significant; Residual Kt/V; total weekly peritoneal urea clearance per urea distribution volume.

Abbreviations: BUN, blood urea nitrogen; Alb, Albumin; P, Phosphorus; K, potassium; Hb, hemoglobin; HDL, high-density lipoprotein; TG, triglyceride.

Figure 2 Changes over the course of PD intervention and cost-effectiveness. The cost-effectiveness tended to gradually deteriorate once PD intervention was initiated (difference became marked from 36 months). Furthermore, the baseline CUA for 12–24 months was significantly better in the PD group than in the HD group. Error bars denote standard error (SE). Statistical significance of population mean difference was analyzed using Welch’s t-test.

Table 2 Comparison of the PD and HD cost-effectiveness (Baseline cost-utility analysis)

Item	PD (Mean±Standard deviation)	HD (Mean±Standard deviation)	Significant difference (p-value)
Utility (EQ−5D score, monthly conversion)	0.825±0.177	0.785±0.181	*
Medical costs (medical department outpatient, US$/month)	3,615±1,435	3,626±439	n. s.
Cost-utility analysis (US$/QALY, annual conversion)	55,019±25,163	58,815±18,347	n. s.

Notes: Welch’s t-test *p < 0.05, n. s.: not significant.

Table 3 Correlation analysis of factors influencing the cost-effectiveness

Item	Correlation analysis
	Population correlation coefficient (ρ)	p-value
Age	−0.158	**
Duration of PD (months)	0.030	0.499
Disease (code)	0.193	**
Residual Kt/V	−0.058	0.199
BUN	0.043	0.345
Alb	0.062	0.379
Ca	0.074	0.209
P	0.172	*
K	−0.144	**
PTH	−0.099	0.050
Hb	0.080	0.070
HDL	−0.130	**
LDL	0.073	0.222
TG	−0.098	*

Notes: Welch’s t-test *p < 0.05, **p < 0.01; When we assessed the significance of the population correlation coefficient using the CUA as the response variable and clinical indices as the predictor variables, we found a strong correlation between cost-effectiveness and age, disease, P, K, HDL, and TG.

Figure 3 A cost-utility analysis by primary disease. Adjusting the baseline CUA by disease revealed that glomerulonephritis had a significantly better CUA than nephropathy. Error bars denote SE. Statistical significance of population mean difference was analyzed using Welch’s t-test.

Figure 4 A medical cost analysis by age. The medical costs for patients in their 50s were significantly higher than those in their 60s and 70s. In general, medical costs for the elderly tended to be lower than those for middle-aged patients (indices in the figure: 5th percentile, first quartile; median, 3rd and 95th percentile; outliers of maximum and minimum). Statistical significance of population mean difference was analyzed using Welch’s t-test.

Figure 5 A cost-utility analysis by age. The baseline CUA was adjusted by age group and showed a tendency for a significantly higher CUA for patients in their 70s than for those in their 50s. Error bars denote SE. Statistical significance of population mean difference was analyzed using Welch’s t-test.

Table 4 Comparison of the CAPD and APD cost-effectiveness and incremental cost-utility ratio

Item (Disease: Diabetic nephropathy, Age: 60–70 years)		APD (Mean±Standard deviation)	CAPD (Mean±Standard deviation)	Significant difference (p-value)
Number of cases	(cases)	9	9	—
Age	(years)	70.1±3.5	70.6±4.2	n. s.
Males	(%)	66.7	55.6	n. s.
Dialysis duration	(months)	18.6±31.7	18.5±16.5	n. s.
Test values
Residual Kt/V		0.9±0.5	0.8±0.2	n. s.
BUN (mg/dL)		44.0±12.7	49.7±13.3	n. s.
Alb (g/dL)		3.4±0.2	3.0±0.6	n. s.
P (mg/dL)		4.9±0.9	4.7±1.2	n. s.
K (mEq/L)		4.3±0.4	4.2±0.5	n. s.
HDL (mg/dL)		50.6±9.3	69.1±37.2	n. s.
TG (mg/dL)		96.4±62.9	165.6±124.0	*
Utility (EQ−5D score, monthly conversion)		0.987±0.039	0.860±0.164	*
Medical costs (medical department outpatient, US$/month)		4,591±1,494	3,275±1,204	**
Cost-utility analysis (US$/QALY, annual conversion)		59,830±19,376	49,023±66,773	*
Incremental cost-utility ratio
(ICUR: CAPD vs. APD calculation)		126,034 (12–24 months after intervention: 74,598)
(US$/QALY, annual conversion)

Notes: Welch’s t-test *p < 0.05, **p < 0.01, n. s.: not significant.