Effects of the Frontiers Prevention Project in Ecuador on sexual behaviours and sexually transmitted infections amongst men who have sex with men and female sex workers: challenges on evaluating complex interventions

Figures & data

Table 1. Socio-demographic characteristics of a sample of men who have sex with men (MSM) and female sex workers (FSW) in Ecuador. Baseline (2003) and follow-up (2007).^a

	MSM (n = 2400)				FSW (n = 2662)
	Baseline (%)		Follow-up (%)		Baseline (%)		Follow-up (%)
	Comparison	FPP	Comparison	FPP	Comparison	FPP	Comparison	FPP
	(n = 479)	(n = 1248)	(n = 211)	(n = 462)	(n = 774)	(n = 752)	(n = 562)	(n = 574)
Age (mean)	26.8	24.8	27.8	25.9^†	28.3	27.2	28.8	28.2
Marital status:
Married/in union	21.8	19.0	31.7	18^†	45.3	46.8	48.8	52.1
Divorced/separated/widowed	3.7	0.7^†	2.8	3.9^‡	4.7	5.3	6.4	5.9
Single	74.5	80.3	65.4	78.1^†	50.0	47.9	44.8	42.0
Has at least one child	31.5	21.7	31.3	23.6	87.5	85.4	89.0	83.6^†
Group of self-identification (MSM only):
Bisexual (active and/or passive)	48.4	43.5	48.8	41.1	N/A	N/A	N/A	N/A
Masculine gay	21.5	31.9^†	20.4	31.4^†	N/A	N/A	N/A	N/A
Heterosexual	8.4	3.6^†	4.7	3.0	N/A	N/A	N/A	N/A
Other	21.8	21	26.1	24.5	N/A	N/A	N/A	N/A
Self-identifies as a sex worker (FSW only)	N/A	N/A	N/A	N/A	84.6	85.0	82.4	83.9
Family is aware of sexual preference (MSM only)	86.5	88.6	82.9	85.5	N/A	N/A	N/A	N/A
Family is aware of sex work (FSW only)	N/A	N/A	N/A	N/A	57.0	59.3	51.6	59.2
Participates in support group	11.1	6.5	10.0	11.0	10.5	8.1	7.3^‡	11.0
Socioeconomic level:
1^st quartile	18.8	24.8	44.5^‡	16.5^†‡	20.5	33.4^†	24.4	27.5
2^nd quartile	27.2	22.5	22.7	26.2	21.6	24.8	24.4	23.9
3^rd quartile	27.0	25.2	21.3	26.8	27.8	22.2^†	24.4^‡	25.4
4^th quartile	26.9	27.4	11.4^‡	30.5^†	30.1	19.7^†	26.9	23.2
Notes: ^aAdjusting by cluster sampling.
^bAssessed only at follow-up.
^† p ≤ 0.05 for the difference between comparison and FPP group within each assessment.
^‡ p ≤ 0.05 for the difference between baseline and follow-up within each group.

Table 2. Socio-demographic caracteristics of a sample of men who have sex with men (MSM) and female sex workers (FSW) in Ecuador. Baseline (2003) and follow-up (2007).^a

			Baseline (%)		Follow-up (%)
MSM (n = 2400)	ρ1	ρ2	Comparison (n = 479)	FPP (n = 1248)	Comparison (n = 211)	FPP (n = 462)
Condom use with male partner	0.01	0.01	37.0	33.0	49.4^‡	76.2^†‡
Condom use with female partner	0.00	0.00	29.9	23.6	40.5	58.1^‡
Syphilis seroprevalence	0.00	0.01	7.0	7.8	10.9	8.2
HSV-2 seroprevalence	0.06	0.07	51.6	45.1	92.9^‡	76.6^†‡
HIV seroprevalence^b	N/A	N/A	N/A	N/A	11.8	8.7
			Comparison	FPP	Comparison	FPP
FSW (n = 2662)	ρ1	ρ2	(n = 774)	(n = 752)	(n = 562)	(n = 574)
Consistent condom use with clients	0.07	0.14	84.5	80.7	98.6^‡	97.0^‡
Condom use with regular partner	0.00	0.00	7.6	5.2	10.8	13.6^‡
Syphilis seroprevalence	0.00	0.02	2.5	3.5	6.8^‡	7.0^‡
HSV-2 seroprevalence	0.03	0.04	87.3	81.0	94.8^‡	89.7
HIV seroprevalence^b	N/A	N/A	N/A	N/A	6.6	3.7
Notes: ^aAdjusting by cluster sampling.
^bAssessed only at follow-up.
^† p ≤ 0.05 for the difference between comparison and FPP group within each assessment.
^‡ p ≤ 0.05 for the difference between baseline and follow-up within each group.
ρ1 = Intracluster correlation coefficient for the 2003 survey with original clusters (cities).
ρ2 = Intracluster correlation coefficient for the 2003 survey with sub-clusters (sites) used in the final analysis.

Table 3. FPP effects on condom use and STIs in a sample of men who have sex with men (MSM) and female sex workers (FSW) in Ecuador (2003–2007).*

		MSM^§				FSW^£
	Condom use with male partner^a	Condom use with female partner^a	Syphilis	HSV-2	HIV	Consistent condom use with clients^b	Condom use with regular partner^c	Syphilis	HSV-2	HIV
(sample size)	(n = 2008)	(n = 1001)	(n = 2400)	(n = 2400)	(n = 673)	(n = 2662)	(n = 1518)	(n = 2662)	(n = 2317)	(n = 1153)
Differences at baseline (FPP = 1)	0.84	0.67*	1.06	0.84		0.96	0.71	1.59	0.93
	(0.56–1.27)	(0.42–1.05)	(0.59–1.94)	(0.46–1.53)		(0.89–1.01)	(0.41–1.20)	(0.89–2.81)	(0.87–0.98)
Time trend (follow-up = 1)
Comparison	3.69	3.70	0.21	58.71	N/A	1.20	1.28	3.48	1.15	N/A
	(1.46–9.30)	(1.27–10.7)	(0.08–0.54)	(23.9–143.7)		(1.15–1.21)	(0.47–3.19)	(1.28–8.46)	(1.06–1.18)
FPP	12.68	10.63	0.06	28.1		1.20	2.31	2.42	1.14
	(4.59–35.1)	(1.1–103.6)	(0.02–0.19)	(9.9–79.8)		(1.12–1.21)	(0.82–5.47)	(0.84–6.38)	(1.03–1.18)
FPP effect	2.89	1.91	0.32	0.40	0.84	0.98	1.29	1.08	0.93	0.75
	(1.34–6.28)	(0.47–7.8)	(0.14–0.72)	(0.11–1.5)	(0.31–2.31)	(0.93–1.00)	(0.85–1.90)	(0.70–1.67)	(0.85–0.99)	(0.42–1.3)
Notes: *Multivariated models adjusting by age, marital status, have any child, family awareness about sexual preferences or sex work, participates in support group, socioeconomic level and average of exposure to intervention activities by city and considering the design effect of cluster sampling; FPP effects estimated by an interaction term (groupXtime) and odds ratio calculated using lincom command in Stata; significative values in bold; HIV models do not include the interaction term thus FPP = 1.
§ = Results are odds ratios.
£ = Results are risk ratios: RR = RM/[(1–P0) + (P0*RM)].
a = Refers to the last intercourse according to sexual partner gender.
b = Refers to last 3 clients.
c = Refers to last intercourse among those who have regular partner.

Table 4. FPP effects on a sub-sample of female sex workers (FSW) in Ecuador, excluding participants from one comparison city due to potential contamination in the data. Results are risk ratios (CI 95%).*

FSM
	Consistent condom use with clients^a	Condom use with regular partner^b	Syphilis	HSV-2	HIV
(sample size)	(n = 2187)	(n = 1243)	(n = 2187)	(n = 1897)	(n = 908)
Differences between groups	0.97	0.62	1.35	0.96
at baseline (FPP = 1)	(0.91–1.03)	(0.34–1.08)	(0.72–2.49)	(0.89–1.01)
Time trend (follow-up = 1)
Comparison	1.20	2.00	0.88	1.20	N/A
	(1.09–1.22)	(0.54–5.83)	(0.28–2.69)	(1.18–1.21)
FPP	1.15	5.92	0.22	1.21
	(0.67–1.21)	(1.40–12.10)	(0.04–1.11)	(1.19–1.21)
FPP effect	0.91	2.16	0.35	1.05	0.91
	(0.62–1.00)	(1.13–3.65)	(0.16–0.74)	(1.00–1.08)	(0.34–2.21)
Notes: *Risk ratios calculated using the formula RR = RM/[(1–P0) + (P0*RM)]. Adjusted by age, marital status, have any child, family awareness about sexual work, participates in support group, socioeconomic level and average of exposure to intervention activities by city and considering the design effect of cluster sampling; FPP effects estimated by an interaction term (groupXtime); significative values in bold; HIV model does not include the interaction term and thus FPP = 1.
^aConsistent condom use with clients refers to last three clients.
^bCondom use with regular partner refers to last intercourse among those who have regular partner.

Figure 1. Average of exposure to specific intervention activities among MSM and FSW by city.