Primary Care Physician Panel Size and Quality of Care: A Population-Based Study in Ontario, Canada

Simone Dahrouge; William Hogg; Jaime Younger; Elizabeth Muggah; Grant Russell; Richard H. Glazier

doi:10.1370/afm.1864

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Table 1

Patient, Physician, and Practice Characteristics Across Panel Size Ranges

Characteristic	Panel Size
Characteristic	All	1,200–1,799	1,800–2,399	2,400–2,999	3,000–3,599	3,600+
Physician profile
Physicians, No.	4,195	2,028	1,351	526	168	122
Age, median (IQR), y	53 (46–59)	51 (44–58)	54 (47–60)	55 (47–60)	54 (47–58)	52 (46–58)
Male, mean %	68.9	59.9	74.7	81.7	76.8	89.3
Foreign trained, mean %	26.9	22.7	27.4	34.2	41.1	39.3
Time since graduation, median (IQR), y	27 (20–34)	25 (18–33)	28 (21–35)	28 (22–35)	28 (21–33)	25 (19–33)
Practice group size, median (IQR), No.	16 (7–30)	15 (7–30)	16 (7–29)	18 (7–31)	17 (7–36)	18 (5–54)
Rurality: RIO index, median (IQR)	2 (0–8)	2 (0–10)	2 (0–8)	2 (0–6)	2 (0–8)	0 (0–3)
Rurality categories, %
Major urban (RIO <10)	76.6	74.0	77.3	81.2	79.1	89.1
Minor urban (RIO 10–45)	20.4	21.8	20.2	17.4	20.9	10.9
Rural (RIO >45)	3.0	4.2	2.5	1.4	0.0	0.0
Patient profile
Patients, No.	8,265,930	3,014,806	2,792,387	1,399,485	547,305	511,947
Proportion virtually rostered, %	12.7	13.6	11.5	12.5	13.0	13.5
Age, median (IQR)	41 (21–56)	41 (22–57)	41 (21–57)	40 (21–56)	38 (20–54)	37 (20–52)
0 to18 y, %	21.5	21	21.1	21.7	23	23.5
19 to <65 y, %	63.9	63.4	63.7	64.3	64.9	65.9
≥65 y, %	14.6	15.7	15.2	14.1	12.1	10.6
Male, %	48.3	46.4	49.0	49.6	49.1	50.6
Recent immigrants, %	10.5	8.4	8.7	11.3	15.8	25.0
Rurality: RIO index, median (IQR)	2 (0–11)	2 (0–14)	2 (0–11)	2 (0–8)	2 (0–8)	0 (0–5)
Rurality categories, %
Major urban (RIO <10)	73.5	70.5	72.9	76.0	76.6	84.0
Minor urban (RIO 10–45)	23.1	24.6	23.9	22.0	22.4	14.7
Rural (RIO >45)	3.4	4.9	3.2	1.0	1.0	1.2
Socioeconomic profile by income quintile (%)
First (lowest)	18.0	16.6	17.3	18.7	22.0	24.3
Second	19.6	18.6	19.4	20.4	21.1	23.0
Third	20.5	19.9	20.6	21.3	20.9	21.3
Fourth	21.6	22.4	21.8	21.0	19.8	18.4
Fifth (highest)	20.3	22.5	20.9	18.6	16.2	13.0
Case mix:^a Resource Utilization Bands (%)
0 (lowest)	13.0	12.5	13.5	13.1	13.0	13.4
1	10.8	10.5	10.8	11.1	11.2	11.2
2	27.2	27.0	27.4	27.1	27.8	27.4
3	40.7	41.2	40.2	40.7	40.4	40.5
4	6.6	6.9	6.5	6.4	6.3	6.3
5 (highest)	1.7	1.8	1.7	1.6	1.4	1.3

IQR = interquartile range; RIO = Rurality Index of Ontario.
↵a The Resource Utilization Bands provide a measure of the health care resource requirements for individuals. The percentage distribution of patients across the 5 Resource Utilization Bands provides a measure of case mix for the population.

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Table 2

Estimated Performance Level in the Fully Adjusted Model for the Corresponding Panel Size

Indicator	Panel size P value	Panel Size
Indicator	Panel size P value	1,200	1,500	1,800	2,100	2,400	2,700	3,000	3,300	3,600	3,900
Cancer screening, % (95% CI)
Breast	<.001	64.6 (63.9–65.3)	64.2 (63.8–64.6)	63.8 (63.4–64.1)	63.4 (63.0–63.8)	63.1 (62.6–63.6)	62.7 (62.2–63.3)	62.4 (61.8–63.0)	62.1 (61.4–62.9)	61.9 (60.8–62.9)	61.6 (60.3–62.9)
Cervical	<.001	63.7 (62.9–64.5)	62.8 (62.3–63.2)	61.9 (61.5–62.3)	61.1 (60.5–61.6)	60.4 (59.8–61.0)	59.9 (59.3–60.6)	59.5 (58.7–60.3)	59.2 (58.1–60.3)	58.9 (57.4–60.5)	58.7 (56.6–60.7)
Colorectal	.01	45.6 (44.3–46.8)	44.6 (43.9–45.4)	43.8 (43.2–44.4)	43.2 (42.5–43.9)	42.9 (42.1–43.8)	43.0 (42.1–43.9)	43.2 (42.1–44.2)	43.5 (42.1–44.9)	44.0 (42.1–45.9)	44.4 (42.0–46.9)
Chronic disease management, % (95% CI)
Diabetes
Eye examination	.75	71.6 (71.1–72.2)	71.8 (71.4–72.1)	71.8 (71.6–72.1)	71.9 (71.6–72.2)	71.9 (71.6–72.3)	72.0 (71.6–72.3)	71.9 (71.5–72.4)	71.9 (71.4–72.4)	71.8 (71.2–72.5)	71.8 (70.9–72.7)
Lipid test	.59	62.8 (61.4–64.1)	63.0 (62.2–63.8)	63.1 (62.5–63.8)	63.3 (62.5–64.1)	63.5 (62.6–64.3)	63.6 (62.7–64.5)	63.7 (62.6–64.8)	63.8 (62.4–65.3)	64.0 (61.9–65.9)	64.1 (61.4–66.6)
HbA_1c test	.11	39.7 (38.2–41.2)	39.3 (38.5–40.2)	39.0 (38.3–39.7)	38.6 (37.8–39.5)	38.3 (37.3–39.3)	37.9 (36.9–39.0)	37.6 (36.3–38.9)	37.2 (35.5–38.9)	36.9 (34.6–39.2)	36.5 (33.6–39.5)
Metformin	.24	89.1 (87.0–90.9)	88.5 (87.1–89.7)	87.9 (86.8–88.8)	87.4 (86.2–88.5)	87.0 (85.6–88.3)	86.8 (85.3–88.1)	86.6 (85.1–88.1)	86.6 (84.9–88.2)	86.6 (84.5–88.5)	86.6 (84.0–88.9)
ACEi/ARB	.19	73.3 (72.6–74.0)	73.5 (73.1–73.9)	73.7 (73.4–74.0)	73.9 (73.5–74.3)	74.0 (73.5–74.4)	74.1 (73.6–74.6)	74.2 (73.7–74.7)	74.2 (73.6–74.9)	74.3 (73.5–75.1)	74.4 (73.3–75.4)
Lipid-lowering agent	.66	69.7 (68.8–70.5)	69.8 (69.3–70.3)	69.9 (69.5–70.3)	70.0 (69.5–70.5)	70.1 (69.5–70.6)	70.1 (69.6–70.7)	70.2 (69.5–70.8)	70.2 (69.4–71.1)	70.3 (69.1–71.4)	70.3 (68.8–71.7)
Other
CHF: ECHO	<.001	69.4 (67.3–71.3)	70.2 (69.0–71.4)	71.1 (70.2–72.0)	71.9 (70.8–72.9)	72.6 (71.4–73.7)	73.2 (72.0–74.4)	73.8 (72.5–75.1)	74.4 (72.8–75.9)	74.9 (72.9–76.8)	75.5 (72.9–77.8)
CHF: ACEi/ARB	.39	67.3 (65.1–69.3)	67.9 (66.6–69.2)	68.5 (67.5–69.4)	68.9 (67.7–70.0)	69.2 (67.9–70.4)	69.3 (67.9–70.6)	69.3 (67.8–70.7)	69.3 (67.5–71.0)	69.2 (66.9–71.4)	69.2 (66.3–71.9)
Asthma: Spirometry	.33	24.9 (22.7–27.3)	24.4 (23.0–25.9)	24.0 (22.9–25.1)	23.6 (22.4–24.9)	23.3 (21.9–24.7)	23.0 (21.5–24.6)	22.8 (21.2–24.4)	22.6 (20.8–24.4)	22.4 (20.3–24.6)	22.2 (19.6–25.1)
Access & Outcomes (RIO <10), % (95% CI)
Admissions for ACSC	.04	12.0 (11.4–12.7)	12.2 (11.7–12.8)	12.4 (12.0–12.9)	12.6 (12.1–13.2)	12.8 (12.2–13.4)	12.9 (12.3–13.5)	13.0 (12.4–13.7)	13.1 (12.4–13.8)	13.2 (12.4–14.0)	13.3 (12.3–14.3)
ED visits, low triage	.004	19.5 (18.7–20.3)	19.0 (18.5–19.4)	18.5 (18.1–18.8)	18.1 (17.7–18.5)	17.8 (17.3–18.3)	17.6 (17.1–18.2)	17.5 (16.9–18.1)	17.4 (16.8–18.1)	17.4 (16.6–18.3)	17.4 (16.3–18.5)
Physician, % (95% CI)
Continuity	<.001	78.0 (77.4–78.5)	78.6 (78.2–78.9)	79.1 (78.8–79.3)	79.3 (79.0–79.7)	79.3 (78.9–79.8)	79.1 (78.7–79.6)	78.7 (78.1–79.2)	78.1 (77.4–78.8)	77.4 (76.5–78.3)	76.7 (75.6–77.9)
Comprehensiveness	.03	66.5 (65.8–67.2)	66.6 (66.2–67.0)	66.7 (66.3–67.0)	66.7 (66.2–67.2)	66.5 (66.0–67.1)	66.3 (65.7–66.9)	66.1 (65.4–66.7)	65.7 (65.0–66.4)	65.4 (64.5–66.3)	65.1 (64.0–66.1)

ACEi = angiotensin-converting enzyme inhibitor; ACSC = ambulatory-care–sensitive conditions; ARB = angiotensin receptor blocker; CHF = congestive heart failure; ECHO = echocardiogram; ED = emergency department; HbA1c = glycated hemoglobin; RIO = Rurality Index of Ontario.
Note: Quality of care indicator performance levels are derived from regression coefficients set at their mean or mode across for panel size intervals. The P values given in the table are omnibus P value that represent the overall effect of the 2 panel-size cubic spline variables produced by the equation.

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The Article in Brief

Primary Care Physician Panel Size and Quality of Care: A Population-Based Study in Ontario, Canada

Simone Dahrouge , and colleagues

Background Where physician resources are scarce, one way to ensure that individuals have a primary care doctor is to promote larger panel sizes (i.e., more patients per doctor). There is a concern, however, that the quality of primary care may decline at larger panel sizes. This study examines the association between family physicians' panel size, quality of care, and health service use.

What This Study Found Among 4,195 physicians in Ontario, Canada with panel sizes between 1,200 and 3,900 patients, increasing panel size is associated with small decreases in cancer screening, continuity, and comprehensiveness, but little difference in chronic disease management quality or indicators of access to care. Specifically, the likelihood of patients? being up-to-date on cervical, colorectal and breast cancer screening shows relative decreases of 8 percent, 6 percent and 5 percent, respectively, with increasing panel size. Eight chronic care indicators show no significant association with panel size, but increasing panel size is associated with an 11 percent relative increase in hospitalization rates for ambulatory-care-sensitive conditions and an 11 percent decrease in non-emergency department visits. Continuity is highest with medium panel sizes and comprehensiveness has a small decrease with increasing panel size.

Implications

According to the authors, these findings do not support policy measures such as thresholds or caps that reduce payments to physicians with large panel sizes.
Physicians who take on larger patient panels may be able to do so without compromising care quality because personal or practice characteristics, such as communication style, organizational climate, and measures to optimize practice access, allow them to provide effective and efficient care.