Table 2.

Association between consent form metrics and federally funded clinical trial dropout rate.

Clinical trial consent form characteristic	Unadjusted, IRR [95% CI]	P-value	Risk-Adjusted, IRR [95% CI]	P-value
Number of pages	1.29 (1.27–1.30)	P < 0.001	1.01 (0.99–1.03)∗	P = 0.305
Flesch-Kincaid Grade Level	1.27 (1.26–1.28)	P < 0.001	1.16 (1.11–1.21)+	P < 0.001

Abbreviations: IRR, incidence rate ratio, 95% CI, 95% confidence interval.

Results taken from (risk-adjusted) negative binomial model that accounted for potential confounding due to baseline differences in enrollment (clinical trial size), subject gender, subject age, primary intervention (drug, behavioral, biological, device, other), study design, study phase, oncologic trial, and the ∗Flesch-Kincaid Grade Level and +number of pages of a clinical trial's consent.

The incident rate ratio represents what occurs to the dropout rate with each additional increase in either the Flesch-Kincaid Grade Level or the number of pages of a clinical trial's consent form. For example, for every 1 grade increase in the Flesch-Kincaid Grade Level, the associated dropout rate increased by approximately 16% according to the risk-adjusted model.