Engineering practice variation through provider agreement: a cluster-randomized feasibility trial

Figures & data

Figure 1 Flow of study subjects.

Abbreviation: VHA, US Veterans Health Administration.

Table 1 Baseline characteristics of study sample

Characteristic	Cluster assignment
	Favor chlorthalidone	Favor HCTZ
Facilities: patients with at least one outpatient prescriptiona (count range)	2,818–31,511	2,818–31,511
Providers: number participating, with at least one prescription	10	8
Publication count 2002–2012 (median, IQR)	0 (0–0)	0 (0–0)
Prior chlorthalidone useb (mean, SD)	1.0 (2.5)	0.5 (1.0)
Patients: number totaled over clusters	77	61
Age, years (mean, SD)	61 (10.8)	60 (13.1)
Male (%)	99	98
Race: white (%)	69	69
Antihypertensive drug count categories (%)c
0	47	49
1	25	25
≥2	29	26

Notes:

a For any medication, in 2012;

b provider summary: % of new starts in 2010–2011;

c active Veterans Health Administration prescriptions in 30 days prior to thiazide start.

Abbreviations: HCTZ, hydrochlorothiazide; IQR, interquartile range; SD, standard deviation.

Table 2 Prescribing outcomes of providers (n=18) over 9 months intervention

Outcomes	Cluster assignment
	Favor chlorthalidone	Favor HCTZ
	n=10	n=8
	Median (interquartile range)	Median (interquartile range)
New thiazide starts by provider (count)	7 (4.0–11.0)	7 (2.5–11.5)
Use of cluster drug (% of provider’s new starts)	80 (54.5–100)	100 (100–100)
During first half of intervention period	100 (83.3–100)	100 (100–100)
During second half of intervention period	63 (10.0–100.0)	100 (100–100)
Within physicians (n=108 prescriptions)	65 (50.0–85.7)	100 (100–100)
Within non-physicians (n=30 prescriptions)	100 (83.3–100.0)	100 (88.9–100.0)
Starting dose in recommended rangea	100 (100–100)	28 (0.0–66.7)
Ever dosed in recommended rangeb	100 (100–100)	45 (22.5–75.0)

Notes:

a Percentage of new starts on cluster drug;

b percentage of new starts on cluster drug, within 6 months of starting drug.

Abbreviation: HCTZ, hydrochlorothiazide.

Table 3 Survey of site investigators

Factor	Median response*
What factors did providers report were important in their decision to participate in the trial?
To contribute to a comparative effectiveness study	Very important
The literature evidence that important questions remain for the two thiazides	Somewhat important
The opinion of colleagues	Somewhat important
For providers randomized to a thiazide other than their pre-study routine choice: What factors were helpful in reminding them of their study drug?
Study beverage mug/cup	Very helpful
Monthly reports	Somewhat helpful
Provider information letter	Very helpful
Patient information letter	Somewhat helpful
Face-to-face interactions with the site investigator	Very helpful

Note:

* Response categories: very, somewhat, not at all.