Association between change in physician remuneration and use of peritoneal dialysis: a population-based cohort analysis

Aaron J. Trachtenberg; Amity E. Quinn; Zhihai Ma; Scott Klarenbach; Brenda Hemmelgarn; Marcello Tonelli; Peter Faris; Robert Weaver; Flora Au; Jianguo Zhang; Braden Manns

doi:10.9778/cmajo.20190132

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Figure 1:
Division of the entire study period for analysis purposes. Fee change 1 = introduction of weekly billing code for patients receiving peritoneal dialysis at $32.16. Fee change 2 = increase in weekly billing code for patients receiving peritoneal dialysis from $49.15 to $70.94. Fee change 3 = introduction of weekly billing code for all dialysis modalities at $135. Note that, during the exclusion period, the weekly billing code for patients receiving peritoneal dialysis was increased from $32.16 to $49.15, but we did not analyze this increase owing to the simultaneous expansion of the salaried program. *Patients who started dialysis during this period were excluded.
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Figure 2:
Flow diagram showing participant selection.
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Figure 3:
Proportion of patients starting long-term dialysis who were receiving peritoneal dialysis at 90 days in each month. For illustrative purposes, separate dashed regression lines for the fee-for-service and salaried groups before and after each fee change are displayed on top of the raw data.

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Table 1:

Characteristics of patients in the fee-for-service and salaried groups during study period 1 (Jan. 1, 2001–Mar. 31, 2004)^*

Characteristic	Fee-for-service, no. (%) of patients^†		Salaried, no. (%) of patients^†

	Before fee change 1 n = 197	After fee change 1 n = 325	Before fee change 1 n = 124	After fee change 1 n = 233
No. of months	15	24	15	24

Age, yr, mean ± SD^‡	62.6 ± 15.9	64.6 ± 15.7	62.7 ± 15.8	59.5 ± 16.1

Female sex	88 (44.7)	154 (47.4)	51 (41.1)	98 (42.1)

Income quintile^§

1 (lowest)	53 (26.9)	72 (22.2)	34 (27.4)	64 (27.5)

2	36 (18.3)	73 (22.5)	27 (21.8)	41 (17.6)

3	33 (16.8)	60 (18.5)	17 (13.7)	49 (21.0)

4	30 (15.2)	46 (14.2)	25 (20.2)	38 (16.3)

5 (highest)	38 (19.3)	54 (16.6)	14 (11.3)	28 (12.0)

Unknown^¶	7 (3.6)	20 (6.2)	7 (5.6)	13 (5.6)

Comorbidities

Alcohol use disorder	14 (7.1)	15 (4.6)	3 (2.4)	14 (6.0)

Cancer, nonmetastatic	14 (7.1)	16 (4.9)	5 (4.0)	11 (4.7)

Chronic heart failure^‡	79 (40.1)	148 (45.5)	40 (32.3)	82 (35.2)

Chronic pulmonary disease^‡	45 (22.8)	113 (34.8)^**	37 (29.8)	62 (26.6)

Dementia	4 (2.0)	10 (3.1)	4 (3.2)	7 (3.0)

Diabetes	115 (58.4)	183 (56.3)	74 (59.7)	130 (55.8)

Myocardial infarction	15 (7.6)	31 (9.5)	10 (8.1)	21 (9.0)

Peripheral vascular disease	21 (10.7)	38 (11.7)	6 (4.8)	19 (8.2)

Stroke/transient ischemic attack	36 (18.3)	71 (21.8)	24 (19.4)	40 (17.2)

Dialysis initiation as inpatient	62 (31.5)	88 (27.1)	39 (31.4)	64 (27.5)

Distance between patient postal code and nearest hemodialysis facility, km^‡^††

< 50	166 (84.3)	290 (89.2)	102 (82.3)	192 (82.4)

50–150	31 (15.7)	33 (10.2)	17 (13.7)	29 (12.4)

> 150	0 (0.0)	2 (0.6)	5 (4.0)	12 (5.2)

Distance between patient postal code and nearest peritoneal dialysis training centre, km^‡^††		^**

< 50	134 (68.0)	249 (76.6)	80 (64.5)	138 (59.2)

50–150	45 (22.8)	64 (19.7)	18 (14.5)	41 (17.6)

> 150	18 (9.1)	12 (3.7)	26 (21.0)	54 (23.2)

Note: SD = standard deviation.
↵* All covariates defined based on the date of dialysis initiation. χ² test was used for categorical variables (Fisher exact test when ≥ 20% of cells had an expected value < 5), and 2-sided 2-sample t test for continuous variables.
↵† Except where noted otherwise.
↵‡ Significant at p < 0.05 for difference between fee-for-service and salaried groups after policy change.
↵§ Estimated with the use of the postal code.
↵¶ These patients had postal codes without neighbourhood income data available.
↵** Significant at p < 0.05 for within-group difference before and after fee change.
↵†† Significant at p < 0.05 for difference between fee-for-service and salaried groups before policy change.

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Table 2:

Characteristics of patients in the fee-for-service and salaried groups during study period 2 (Apr. 1, 2005–Dec. 31, 2014)^*

Characteristic	Fee-for-service, no. (%) of patients^†			Salaried, no. (%) of patients^†

	Before fee change 2 n = 316	Between fee changes 2 and 3 n = 335	After fee change 3 n = 1065	Before fee change 2 n = 279	Between fee changes 2 and 3 n = 236	After fee change 3 n = 889
No. of months	24	24	69	24	24	69

Age, yr, mean ± SD^‡	64.1 ± 15.5	62.91 ± 15.7	63.4 ± 14.6	63.1 ± 15.1	63.2 ± 14.1	61.3 ± 15.6

Female sex	132 (41.8)	116 (34.6)	424 (39.8)	111 (39.8)	84 (35.6)	333 (37.5)

Income quintile^§			^¶

1 (lowest)	85 (26.9)	87 (26.0)	300 (28.2)	80 (28.7)	56 (23.7)	238 (26.8)

2	73 (23.1)	78 (23.3)	235 (22.1)	60 (21.5)	57 (24.2)	208 (23.4)

3	62 (19.6)	66 (19.7)	187 (17.6)	41 (14.7)	42 (17.8)	153 (17.2)

4	53 (16.8)	60 (17.9)	154 (14.5)	53 (19.0)	41 (17.4)	133 (15.0)

5 (highest)	43 (13.6)	42 (12.5)	135 (12.7)	45 (16.1)	36 (15.2)	124 (13.9)

Unknown^**	0 (0.0)	2 (0.6)	54 (5.1)	0 (0.0)	4 (1.7)	33 (3.7)

Comorbidities

Alcohol use disorder	19 (6.0)	22 (6.6)	69 (6.5)	113 (40.5)	21 (8.9)	68 (7.6)

Cancer, nonmetastatic	14 (4.4)	15 (4.5)	63 (5.9)	11 (3.9)	16 (6.8)	65 (7.3)

Chronic heart failure^††	150 (47.5)	147 (43.9)	447 (42.0)	100 (35.8)	93 (39.4)	351 (39.5)

Chronic pulmonary disease	101 (32.0)	105 (31.3)	328 (30.8)	85 (30.5)	96 (40.7)	265 (29.8)

Dementia	14 (4.4)	15 (4.5)	43 (4.0)	6 (2.2)	8 (3.4)	38 (4.3)

Diabetes	185 (58.5)	201 (60.0)	760 (71.4)^¶	151 (54.1)	139 (58.9)	565 (63.6)^¶

Myocardial infarction	42 (13.3)	53 (15.8)	167 (15.7)	33 (11.8)	46 (19.5)	140 (15.7)

Peripheral vascular disease	26 (8.2)	34 (10.1)	108 (10.1)	24 (8.6)	28 (11.9)	105 (11.8)

Stroke/transient ischemic attack	69 (21.8)	65 (19.4)	264 (24.8)	55 (19.7)	52 (22.0)	211 (23.7)

Dialysis initiation as inpatient^‡^††	126 (39.9)	130 (38.8)	440 (41.3)	89 (31.9)	81 (34.3)	320 (36.0)

Distance between patient postal code and nearest hemodialysis facility, km^‡

< 50	286 (90.5)	299 (89.2)	957 (89.9)	239 (85.7)	209 (88.6)	776 (87.3)

50–150	28 (8.9)	29 (8.7)	89 (8.4)	37 (13.3)	23 (9.7)	102 (11.5)

> 150	2 (0.6)	7 (2.1)	19 (1.8)	3 (1.1)	4 (1.7)	11 (1.2)

Distance between patient postal code and nearest peritoneal dialysis training centre, km^‡^††^‡‡			^¶

< 50	229 (72.5)	216 (64.5)	790 (74.2)	199 (71.3)	164 (69.5)	645 (72.6)

50–150	66 (20.9)	84 (25.1)	193 (18.1)	34 (12.2)	35 (14.8)	99 (11.1)

> 150	21 (6.6)	35 (10.4)	82 (7.7)	46 (16.5)	37 (15.7)	145 (16.3)

Note: SD = standard deviation.
↵* All covariates defined based on the date of dialysis initiation. χ² test used for categorical variables (Fisher exact test when ≥ 20% of the cells had an expected value < 5); for continuous variables, analysis of variance when comparing time intervals within group, and 2-sided 2-sample t test when comparing between groups.
↵† Except where noted otherwise.
↵‡ Significant at p < 0.05 for difference between fee-for-service and salaried groups after policy change 2.
↵§ Estimated with the use of the postal code.
↵¶ Significant at p < 0.05 for within-group difference between the 3 time periods.
↵** These patients had postal codes without neighbourhood income data available.
↵†† Significant at p < 0.05 for difference between fee-for-service and salaried groups before policy change 1.
↵‡‡ Significant at p < 0.05 for difference between fee-for-service and salaried groups in the period between policy changes 1 and 2.

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Table 3:

Results of individual patient-level analysis of peritoneal dialysis use 90 days after initiation of long-term dialysis before and after fee changes^*

Model^†	OR		Differences-in-differences estimator (95% CI)^‡
Model^†	Fee-for-service post–pre	Salaried post–pre	Differences-in-differences estimator (95% CI)^‡
Fee change 1 (Apr. 1, 2002)
Unadjusted	0.81	1.12	0.72 (0.35–1.48)
Adjusted^§	0.83	0.94	0.89 (0.44–1.81)
Fee change 2 (Apr. 1, 2007)
Unadjusted	1.10	0.88	1.24 (0.86–1.80)
Adjusted^§	1.03	0.89	1.15 (0.73–1.83)
Fee change 3 (Apr. 1, 2009)
Unadjusted	1.17	0.90	1.31 (0.87–1.80)
Adjusted^§	1.31	0.87	1.52 (0.96–2.40)

Note: CI = confidence interval, OR = odds ratio.
↵* The same subset of data served for the periods after fee change 2 and before fee change 3.
↵† Fee change 1: weekly fee-for-service remuneration for peritoneal dialysis introduced at $32.16; fee change 2: weekly fee-for-service remuneration for peritoneal dialysis increased from $49.15 to $70.94; fee change 3: weekly fee-for-service remuneration for all patients receiving dialysis $135.
↵‡ The differences-in-differences estimator is the odds ratio for peritoneal dialysis use in the fee-for-service group after versus before a fee change, divided by the odds ratio for peritoneal dialysis use in the salaried group after versus before a fee change.
↵§ Adjusted model controlled for patient-level covariates shown in Tables 1 and 2.