Impossibility to eliminate observer effect in the assessment of adherence in clinical trials

Figures & data

Table 1 Study group characteristics

Characteristics	Functional DA group (Group 1)	No DA alarms group (Group 2)	Nonfunctional DA group (Group 3)
Male/female patients	8/12	9/11	4/1
Age in years: mean ± SD	68.15±12.77	66.26±11.1	66.8±14.62
Race: AA, C, A	6, 13, 1	8, 11, 1	3, 1, 1
POAG	11	11	2
Number of medications
Only 1	9	17	1
Two	6	2	2
Three	5	1	2
Dropout reasons	1 died	3 device malfunctions, 2 devices unable to recover data	none

Abbreviations: SD, standard deviation; AA, African American; C, Caucasian; A, Asian; POAG, primary open angle glaucoma; DA, Travoprost Dosing Aid.

Table 2 Association of group membership and questionnaire response

Question	Number (%) with positive response			P-value for exact chi-square test of differences among three groups
	Group 1 (n=20)	Group 2 (n=19)	Group 3 (n=5)
1. Are you missing more than one drop per week on average?	1 (5)	6 (32)	0 (0)	0.056
2. Do you like the DA?	17 (85)	14 (74)	5 (100)	0.35
3. Do you feel as if you were monitored by the DA?	16 (80)	14 (74)	2 (40)	0.20
4. Did the DA affect your drop use?	10 (50)	4 (21)	4 (80)	0.029
5. Would you recommend the DA?	17 (85)	14 (74)	5 (100)	0.35
6. Would you continue to use the DA?	16 (80)	14 (74)	5 (100)	0.45

Notes: Group 1: fully functional; Group 2: no alarms; Group 3: nonfunctional.

Abbreviation: DA, Travoprost Dosing Aid.

Table 3 Association between responses to questionnaire and adherence by group

Question	Group	Odds ratio (adherence vs no adherence – yes vs no)	95% confidence interval		P-value
			Lower	Upper
1. Are you missing more than one drop per week on average	1 2	1.11 0.57	0.62 0.28	1.97 1.16	0.73 0.12
2. Do you like the DA?	1 2	2.11 1.95	0.42 0.39	10.59 9.79	0.36 0.42
3. Do you feel as if you were monitored by the DA?	1 2	1.77 4.97	0.46 0.71	6.91 34.78	0.41 0.11
4. Do you feel that the DA affected your drop use?	1 2	1.33 3.07	0.45 1.10	3.88 8.59	0.60 0.03
5. Would you recommend the DA?	1 2	2.11 1.95	0.42 0.39	10.59 9.79	0.36 0.42
6. Would you continue using the DA?	1 2	2.11 1.95	0.42 0.39	10.59 9.79	0.36 0.42

Notes: Group 1 (n=19): functional DA; Group 2 (n=15): no DA alarms.

Abbreviation: DA, Travoprost Dosing Aid.