A systematic review pooling five RCTs finds a significant pooled OR of 0.65 (95% CI: 0.50–0.85; I² = 68%) for a new antihypertensive. The high I² value indicates:

• A The study results are statistically significant and reliable
• B Publication bias is present in the included studies
• C The number of studies is insufficient for meta-analysis
• D Substantial heterogeneity that limits the validity of the pooled estimate ✓

Explanation

I² quantifies the proportion of total variation across studies attributable to heterogeneity rather than chance. An I² ≥ 50% is conventionally considered substantial heterogeneity, meaning the treatment effect estimates differ systematically across studies, which undermines the biological or clinical meaning of the pooled OR. Publication bias is assessed by funnel plot asymmetry (Egger's test), not I². Statistical significance of the pooled result is separate from heterogeneity.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

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