Table 3. Potential prespecified sources of heterogeneity explored among studies reportingan association between psoriasis and COPD.

Prespecified source of heterogeneity	No. of studies	Random-effects meta-regression (95% CI)	P-value
Study location			0.240
Europe	1	0.025(1.144–2.118)
Asia	3	0.025(1.069–1.455)
Other	0	N/A
Source population			0.454
Inpatient	0	N/A
Outpatient	1	0.312(0.150–2.704)
No distinction	3	0.312(0.370–6.665)
Study design			0.360
Case–control	2	0.013(0.506–0.792)
Cohort	2	0.013(1.262–1.976)
Study quality			0.630
High-quality(≥7stars)	2	0.700(0.180–4.023)
Medium-quality(4–6stars)	2	0.700 (0.249–5.545)
poor-quality(<4stars)	0	N/A
Severity of psoriasis			0.690
No distinction	2	0.700 (0.180–4.023)
Mild vs. severe	2	0.700 (0.249–5.545)
Psoriatic arthritis included			1.000
No	0	N/A
Yes	2	0.985(0.193–5.109)
Not clear	2	0.985(0.196–5.191)
Outcome ascertainment			0.500
Billing data	1	0.312(0.150–2.704)
Chart review	3	0.312(0.370–6.665)
Examination	0	N/A

CI, confidence interval; N/A, not applicable.