Quality of Diabetes Care in Family Medicine Practices: Influence of Nurse-Practitioners and Physician’s Assistants

Pamela A. Ohman-Strickland; A. John Orzano; Shawna V. Hudson; Leif I. Solberg; Barbara DiCiccio-Bloom; Dena O’Malley; Alfred F. Tallia; Bijal A. Balasubramanian; Benjamin F. Crabtree

doi:10.1370/afm.758

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Table 1.

Description of Dependent Variables: Components of Diabetes Guidelines

HbA_1c=hemoglobin A_1c; LDL = low-density lipoprotein; BP = blood pressure; ACE=angiotensin-converting enzyme; ARB=angiotensin receptor blocker.

Assessment

HbA_1c test in the last 6 months

LDL-cholesterol test in the last 12 months

Microalbumin test in the last 12 months

BP check at every visit

Treatment

HbA_1c ≤ 8%, or >8% and on a hypoglycemic agent

LDL-cholesterol ≤ 100 mg/dL, or >100 mg/dL and on a lipid- lowering agent

BP ≤ 130/85 mm Hg, or >130/85 mm Hg and on an antihypertensive agent

Microalbumin in urine >30 mg in 24 hr and on an ACE inhibitor or ARB

Target attainment

HbA_1c ≤ 7%

LDL-cholesterol ≤ 100 mg/dL

BP ≤ 130/85 mm Hg

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Table 2.

Items From the Survey of Organizational Attributes for Primary Care (SOAPC)³² and the Competing Values Framework (CVF)³⁴

SOAPC items

Communication

1. When there is a conflict in this practice, the people involved usually talk it out and resolve the problem successfully.
2. Our staff has constructive work relationships.
3. There is often tension between people in this practice.
4. The staff and clinicians in this practice operate as a real team.

Practicewide decision making

5. This practice encourages staff input for making changes and improvements.
6. All of the staff participates in important decisions about the clinical operation.
7. The practice defines success as teamwork and concern for people.
8. Staff are involved in developing plans for improving quality.

Nurses’ participation in decision making

9. This practice encourages nursing and clinical staff input for making changes and improvements.
10. Practice leadership discourages nursing staff from taking initiative.

Busyness

11. It’s hard to make any changes in this practice because we’re so busy seeing patients.
12. The staff members of this practice very frequently feel overwhelmed by the work demands.
13. The clinicians in this practice very frequently feel overwhelmed by the work demands.
14. Practice experienced as “stressful.”
15. This practice is almost always in chaos.
16. Things have been changing so fast in our practice that it is hard to keep up with what is going on.

History of change

17. Our practice has changed in how it takes initiative to improve patient care.
18. Our practice has changed in how it does business.
19. Our practice has changed in how everyone relates.

CVF items pertaining to market orientation

The practice is a very controlled and structured place. Formal procedures generally govern what people do.
The leadership in the practice is generally considered to exemplify coordinating, organizing, or smooth-running efficiency.
The management style in the practice is characterized by security of employment, conformity, predictability, and stability in relationships.
The glue that holds the practice together is formal rules and policies. Maintaining a smooth- running organization is important.
The practice emphasizes permanence and stability. Efficiency, control, and smooth operations are important.
The practice defines success on the basis of efficiency. Dependable delivery, smooth scheduling, and low-cost production are critical.

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Table 3.

Comparison of Practice Characteristics Across Practices

Characteristic	Practices With NPs (n=9)	Practices With PAs (n=9)	Practices With Physicians Only (n=28)	P Value	Total or Mean (N=46)
NP = nurse-practitioner; PA = physician’s assistant.
^a Values are numbers (percentages) of practices in each classiffication. P values are calculated using the permutation test with the Pearson χ² test statistic.
^b Values are means (standard deviations) of the practice staff summary statistics. P values are based on analysis of variance.
^c P value are based on practices with either PAs or NPs.
Practice classiffication^a
Number of physicians
1	1 (11.1)	0 (0)	8 (28.6)	.02	9
2–4	8 (88.9)	4 (44.4)	15 (53.6)		27
5–8	0 (0)	5 (55.6)	5 (17.9)		10
Has a diabetes registry	1 (11.1)	4 (44.4)	3 (10.7)	.08	8
Uses nurses or health educators for diabetes counseling	2 (22.2)	2 (22.2)	8 (28.6)	1.00	12
Counsels for physical activity, eating, and tobacco	1 (11.1)	0 (0)	2 (7.1)	1.00	3
Counsels for physical activity or eating or tobacco	1 (11.1)	1 (11.1)	5 (17.9)	1.00	7
Performs health risk assessment for physical activity, eating, and tobacco	0 (0)	2 (22.2)	7 (25.0)	.33	9
Performs health risk assessment for physical activity or eating or tobacco	0 (0)	6 (66.7)	13 (46.4)	.18	19
Has a reminder system	6 (66.7)	5 (55.6)	15 (53.6)	.91	26
Practice staff summary^b
Total number of staff	13.7 (4.4)	30.0 (10.8)	12.1 (9.4)	<.001	15.9 (11.3)
Number of NPs or PAs	1.1 (0.3)	1.9 (1.1)	0 (0)	.02	0.6 (0.5)
Proportion of NPs or PAs	8.8 (3.1)	6.1 (2.4)	0 (0)	.13^c	2.9 (3.4)

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Table 4.

Comparison of Characteristics of Diabetic Patients Across Practices

Characteristic	Practices With NPs (n=9)	Practices With PAs (n=9)	Practices With Physicians Only (n=28)	P Value^a	Overall (N=46)
NP = nurse-practitioner; PA = physician’s assistant; CAD = coronary artery disease. Note: Values are means (SDs).
^a Determined by analysis of variance.
Male, %	49.1 (16.3)	51.3 (13.4)	48.3 (14.8)	.87	49.1 (14.5)
Age, mean years	62.7 (5.3)	59.6 (5.9)	59.9 (4.8)	.31	60.4 (5.1)
Comorbidity, %
No CAD or hypertension	29.9 (13.2)	44.6 (21.0)	31.3 (13.3)	.06	33.6 (15.7)
CAD only	7.8 (9.7)	3.9 (6.0)	4.2 (4.7)	.29	4.8 (6.2)
Hypertension only	48.3 (23.3)	42.6 (17.7)	55.3 (13.6)	.12	51.4 (17.0)
CAD and hypertension	14.0 (10.8)	8.9 (7.4)	9.2 (10.4)	.43	10.1 (10.0)

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Table 5.

Adjusted Probabilities of Appropriate Assessment, Treatment, and Target Attainment Among Diabetic Patients by Practice Type

		% (95% CI)			Pairwise Comparison, Rate Ratio (P Value)
Measure	Total No. of Patients	Practices With NPs (n=9)	Practices With PAs (n=9)	Practices With Physicians Only (n=28)	NP vs PA	NP vs Physician-Only	PA vs Physician-Only
CI = confidence interval; NP = nurse-practitioner; PA = physician’s assistant; HbA_1c = hemoglobin A_1c; BP = blood pressure; NA = not applicable.
Note: Probabilities were adjusted for patient-level covariates (age, sex, comorbid conditions, number of visits in last 2 years) and practice-level covariates (solo practice or not, diabetes registry, nurse or health educator for diabetes counseling, reminder system, total staff size).
^a Significant after controlling the false-discovery rate at .05 via the Hochberg procedure for multiple testing.
^b Credit given if assessed appropriately and within target, or if treated according to guidelines.
^c Because rates of treatment were so high, models could not differentiate the effects of NP or PA practice type after accounting for additional patient and practice covariates.
^d Includes only patients who were assessed; credit given if at target or treated according to guidelines.
^e Credit given if assessed appropriately and within target.
^f Includes only patients who were assessed; credit given if at target.
Assessed (all patients)
HbA_1c in last 6 months	846	65.5 (57.7–72.5)	33.4 (17.9–53.4)	48.9 (36.8–61.2)	1.96 (.005)^a	1.34 (<.001)^a	0.68 (.21)
BP at last 3 visits	846	80.1 (64.1–90.0)	75.0 (47.5–90.8)	83.2 (74.3–89.4)	1.06 (.72)	0.96 (.63)	0.90 (.50)
Lipids in last 12 months	846	80.1 (72.6–86.0)	58.2 (45.4–69.9)	68.3 (55.3–78.9)	1.37 (.004)^a	1.17 (.007)^a	0.85 (.29)
Microalbumin in last12 months	846	31.9 (14.1–57.1)	6.1 (2.7–13.3)	18.6 (10.8–30.1)	5.26 (<.001)^a	1.72 (.10)	0.33 (.02)^a
Treated or assessed and at target (all patients)^b
HbA_1c unadjusted^c	846	98.2	99.4	100.0	NA	NA	NA
BP	846	76.1 (61.4–86.5)	81.5 (72.7–87.9)	78.3 (69.5–85.2)	0.93 (.48)	0.97 (.72)	1.04 (.58)
Lipids	846	76.6 (66.6–84.4)	55.9 (43.4–67.8)	65.7 (60.1–71.0)	1.37 (.004)^a	1.17 (.03)	0.85 (.20)
Microalbumin	846	79.6 (61.7–90.5)	61.4 (34.7–82.6)	65.7 (53.5–76.1)	1.30 (.26)	1.21 (.11)	0.93 (.79)
Treated or at target (only if assessed)^d
HbA_1c unadjusted^c	439	100.0	100.0	100.0	NA	NA	NA
BP	653	78.0 (63.9–87.7)	81.8 (72.3–88.5)	79.0 (71.1–85.3)	0.95 (.63)	0.99 (.86)	1.04 (.64)
Lipids	566	77.2 (65.3–85.9)	64.7 (52.2–75.5)	72.0 (62.8–79.7)	1.19 (.09)	1.07 (.32)	0.90 (.37)
Microalbumin	166	98.2 (92.8–99.6)	86.4 (45.4–98.0)	97.7 (87.5–99.6)	1.13 (.07)	1.01 (.71)	0.88 (.09)
Assessed and at target (all patients)^e
HbA_1c	846	50.7 (37.3–64.0)	48.6 (34.6–62.8)	44.5 (36.5–52.7)	1.04 (.84)	1.14 (.36)	1.09 (.63)
BP	846	36.5 (25.0–49.8)	45.0 (31.5–59.2)	47.3 (36.9–58.0)	0.81 (.44)	0.77 (.13)	0.95 (.35)
Lipids	846	53.5 (45.0–61.8)	36.8 (30.8–43.1)	54.4 (49.0–59.8)	1.45 (.001)^a	0.98 (.85)	0.68 (<.001)^a
At target (only if assessed)^f
HbA_1c	439	52.9 (41.9–63.6)	54.5 (35.7–72.2)	59.0 (50.5–67.1)	0.97 (.89)	0.90 (.34)	0.92 (.69)
BP	653	37.7 (24.2–53.3)	45.8 (31.8–60.6)	46.0 (36.1–56.3)	0.83 (.51)	0.82 (.32)	1.00 (.98)
Lipids	566	47.5 (38.6–56.7)	35.6 (27.5–44.5)	48.9 (41.4–56.5)	1.33 (.047)	0.97 (.78)	0.73 (.04)

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Table 6.

Comparison of Organizational Attributes and Market Orientation Across Practices

				Minimum Pairwise Adjusted P Value
Measure	Practices With NPs^a (n=9)	Practices With PAs^a (n=9)	Practices With Physicians Only^a (n=28)	Practice Level^b	Staff Level^c
NP = nurse-practitioner; PA = physician’s assistant; SEM = standard error of the mean.
Note: Organizational attributes are expressed as mean (SEM) scores on scales ranging from 1 to 5, where higher scores indicate stronger staff endorsement of the attribute; market orientation is expressed as the No. (%) of practices that had above-median staff ratings for being market driven.
^a Unadjusted practice-level scores.
^b Calculated using analysis of covariance with practice-averaged scores as the response variable, controlling for practice size.
^c Calculated using hierarchical models with staff members’ responses as the response variable, controlling for staff member sex and role within the practice as well as practice size.
^d Shows marginal significance between physician-only practices and practices with NPs. No other pairwise comparisons had P values <.05.
Organizational attributes, mean (SEM)
Busyness	3.16^d (0.20)	3.18 (0.20)	2.66^d (0.12)	.03^d	.04^d
Practicewide decision making	3.31 (0.21)	3.06 (0.20)	3.48 (0.12)	.55	.28
Participation of nurses in decision making	3.71 (0.19)	3.49 (0.17)	3.79 (0.11)	.82	.66
Communication	3.30 (0.21)	3.02 (0.20)	3.57 (0.12)	.31	.21
Change	3.03 (0.16)	3.24 (0.17)	3.01 (0.10)	.68	.22
Market orientation, No. (%)	3 (33)	6 (67)	14 (50)	.26	.24

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The Article in Brief

Quality of Diabetes Care in Family Medicine Practices: Influence of Nurse-Practitioners and Physician's Assistants

Pamela A. Ohman-Strickland, PhD , and colleagues

Background Growing numbers of nurse-practitioners (NPs) and physician?s assistants (PAs) are providing care in primary care practices. This study examines the effect of NPs and PAs on the quality of care delivered in the primary care setting. In particular, the study focuses on the care of diabetes patients.

What This Study Found Family medicine practices with NPs perform better at providing some types of diabetes care (primarily monitoring tests) than practices with doctors only, and they perform especially better than practices using physician?s assistants.

Implications

The reasons for these results are not yet clear. Additional research needs to explore whether the results are due to NPs and PAs or the practices that hire them.
Future research should also aim to find the best roles for different clinicians working in teams, so that they can have the greatest impact on patient care.