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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 3.

Meta-analysis results for the higher-morbidity population sample 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 7 666,710.60 −4.20 0.05 0.01 68%
Visits
Primary care 10 408.11 −0.56 0.42 <0:001 63
Specialty care 9 341.74 −0.62 0.27 0.26 21
ED, potentially avoidable 9 27.99 −1.00 0.48 0.01 66
ED, all 9 69.41 −0.16 0.90 <0:001 75
Inpatient, ambulatory care–sensitive 8 4.17 −6.95 0.14 0.02 58
Inpatient, all 10 23.21 −0.65 0.75 0.01 64
Cancer Screening
Cervical 5 32.21 1.18 0.64 0.08 52
Breast 8 43.94 1.43 0.01 0.61 0
Colorectal 7 33.29 0.66 0.64 0.06 51
Tests for patients with diabetes
Eye exam 8 45.98 −1.78 0.52 <0:001 96
HbA1c test 8 73.46 0.10 0.85 0.16 34
Lipid test 6 80.30 −0.10 0.86 0.32 15

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.