Table 4 Response to second reminder in RCT B by first reminder received

n

%

n

%

n

%

n

%

Completed questionnaires returned

18

8.1

10

9.1

16

6.3

25

19.8

Absolute percentage difference (95% CI) compared to full questionnaire/full questionnaire combination; p-value

  Full/Abridged

-1.0 (− 7.6, 5.5); 0.77

  Postcard/Full

1.8 (−2.9, 6.5); 0.45

  Postcard/Abridged

-11.7 (−19.5, -3.9); 0.002

Logistic regression model odds ratios (95% CI); p-value

  Abridged

1.13 (0.50, 2.53); 0.77

  Postcard

0.76 (0.38, 1.53); 0.45

  Interaction (Abridged * Postcard)

3.25 (1.13, 9.29); 0.028