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Table 2 Numbers of participants sent an invitation letter, number for whom the letter was returned to sender, and the numbers of participants referred to a fieldworker for a home visit (the number and percentage in each arm are shown)

From: A randomised controlled trial comparing opt-in and opt-out home visits for tracing lost participants in a prospective birth cohort study

Number of participants sent an invitation letter

Opt-in N = 145

Opt-out N = 139

Returned to sender

12 (8 %)

14 (10 %)


3 (2 %)


Referred for home visit

15 (10 %)a

139 (100 %)

  1. aWould have been 3 (2 %) if ‘returned to sender’ not included