Unannounced phone-based pill counts for monitoring antiretroviral medication adherence in South Africa

Figures & data

Table 1. Descriptive characteristics for pills counted to calculate ART adherence for all participants taking first and second line ART.

	1^st Line ART (N = 455)		2^nd Line ART (N = 27)
Variable	N	%	N	%	X^2	v
ART Doses/day
1 Dose	451	99	12	44	201.2**	0.64
2 Doses	4	1	15	56
ART pills/dose
1 Pill	451	99	19	70	86.7**	0.42
2 Pills	4	1	8	30
	M	SD	M	SD	t	d
Pills counted	92.6	60.8	288.3	208.3	4.8**	1.27

Note: ART = antiretroviral therapy.

**p < .01; d = Cohen’s d; v = Cramer’s v.

Table 2. Adherence distributions for unadjusted, censored and subtracted adjustments for over-adherence.

	Unadjusted Adherence		Censored Adherence (>100% = 100%)		Subtracted Adherence (>100% value – 200%)
	N	%	N	%	N	%
< 70%	42	9.7	42	9.7	48	11
< 80%	81	18.6	81	18.6	92	21.1
< 90%	160	36.8	160	36.8	188	43.2
Mean	91.2		89.3		87.5
SD	17.2		14.8		14.8
Median	96.4		96.4		92.8

Table 3. Differences in adherence by gender, alcohol use, ART regimen, and viral load.

	% ART Adherence
Characteristic	M	SD	t	d
Gender
Men	84.7	16.1	2.2*	.24
Women	88.4	14.2
Alcohol use
Currently drinking alcohol	86.1	15.8	2.3*	.23
Not currently drinking alcohol	89.5	12.8
ART regimen
1^st Line	87.9	14.7	2.7**	.56
2^nd Line	79.7	14.8
Viral load
Undetectable (≤ 100 copies)	88.0	14.6	1.9*	.26
Detectable (> 100 copies)	84.1	15.3

Note: ART = antiretroviral therapy.

*p < .05.

**p < .01; d = Cohen’s d.

Table 4. Differences in age and health characteristics between lower and higher adherence groups.

	Lower adherence (< 90%) (n = 188)		Higher adherence (> 90%) (N = 246)
Characteristic	M	SD	M	SD	t	d
Age	37.8	9.6	37.1	9.3	0.8	.08
Log Viral Load	0.69	1.3	0.45	1.1	2.0*	.19
CD4 cell count	573.0	308.0	645.7	363.4	2.2*	.21
Alcohol use (AUDIT-c) score	2.6	2.7	1.6	2.4	3.8	.37
Call attempts for first pill count	2.5	1.8	2.2	1.5	1.9	.18
Call attempts for second pill count	2.3	1.5	2.4	1.7	0.4	.04
	N	%	N	%	X^2	v
History of TB	70	37	94	38	5.4	.11
CD4 < 500 cells/mL	85	45	2.2	1.5	2.2	.07
Elevated serum creatinine	12	6	5	2	5.4	.11

Note: ART = antiretroviral therapy; TB = tuberculosis.

*p < .05.

**p < .01; d = Cohen’s d; v = Cramer’s v.

Table 5. Differences in clinic experiences and medication management between lower and higher adherence groups.

	Lower adherence (<90%) (n = 188)		Higher adherence (>90%) (N = 246)
Clinic and ART Experiences	n	%	n	%	X^2	v
Healthcare worker discussed side- effects at last clinic visit	66	35	69	27	2.5	.07
Healthcare worker asked about missing ART at last clinic visit	71	37	75	30	2.5	.07
Ran out of ART^a	12	6	5	2	5.3*	.11
Stored ART out of bottles so others would not know they are ART^a	17	9	24	6	0.1	.04
Intentional non-adherence^a
Skipped ART when with other people	14	7	8	3	3.8*	.09
Skipped ART when others were nearby	37	19	16	6	17.2**	.19
Skipped because of side-effects	19	10	7	2	9.9**	.15
Skipped because body is sensitive	16	8	8	3	5.6*	.11
Skipped ART when drinking alcohol	45	35	25	22	4.9*	.14
Skipped ART because did not have food to take with pill	17	9	12	5	2.9	.08
ART management
Uses pill box	47	25	16	6	29.6**	.26
Carries medications
Never carries medications	40	21	72	29	4.3	.10
Carries daily; work or school	8	4	14	5
Carries periodically; weekends and when traveling	140	75	161	65
ART Management
Shares medications with others	22	11	20	8	1.5	.06
Borrows medications from others	19	4	16	3	1.9	.06
Has lost medications	18	9	17	6	1.0	.04
Throws away excess medications	36	19	47	19	0.1	.01
Removes medications from bottles	8	4	13	5	0.2	.02

Note: ^a past month.

*p < .05.

**p < .01; d = Cohen’s d; v = Cramer’s v.

Data availability statement

Data are retained by the authors and available upon reasonable request.