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. Author manuscript; available in PMC: 2017 Aug 14.
Published in final edited form as: Health Aff (Millwood). 2017 Mar 1;36(3):500–508. doi: 10.1377/hlthaff.2016.1235

Exhibit 2.

Meta-analysis results for all patients in patient-centered medical homes and comparison practices

p value of:
Measure Number of
studies		 Adjusted average
baselinea 		DID estimate
(% of baseline)b 		DID regression
estimateb 		Chi-square test
of heterogeneityc 		I2d
Cost excluding pharmacy 7 413,435.20 −2.25 0.20 <0:001 88%
Visits
Primary care 11 260.76 −0.53 0.37 <0:001 79
Specialty care 10 173.88 −1.48 <0:001 0.37 8
ED, potentially avoidable 10 9.67 −0.63 0.61 <0:001 72
ED, all 11 29.79 −0.14 0.94 <0:001 89
Inpatient, ambulatory care–sensitive 10 0.82 −2.42 0.58 0.06 47
Inpatient, all 11 8.66 −0.12 0.95 0.001 66
Cancer Screening
Cervical 7 42.26 1.16 <0:001 0.91 0
Breast 9 43.20 0.71 0.14 0.19 29
Colorectal 8 30.02 −0.85 0.61 <0:001 91
Tests for patients with diabetes
Eye exam 9 41.96 −1.75 0.58 <0:001 97
HbA1c test 9 67.19 0.30 0.51 0.08 43
Lipid test 7 74.20 0.44 0.49 0.10 43

SOURCE Authors’ analysis of study data. NOTES ED is emergency department. HbA1c is hemoglobin A1c.

a

Per 1,000 patient-months, except cost excluding pharmacy, which is reported in dollars.

b

DID is difference-in-differences, referring to the difference between the change in the intervention practices from the pre to the post period and the change in the comparison practices from the pre to the post period.

c

The chi-square test of heterogeneity tests the overlap between the confidence intervals of estimates from all studies included in the meta-analysis model. A p value of 0.05 or less indicates significant heterogeneity across study estimates.

d

The I2 statistic quantifies the inconsistency across estimates from studies included in the meta-analysis. The greater the I2 percentage, the greater the inconsistency, and the conventional threshold above which heterogeneity is considerable is 75 percent.