A comparative impact evaluation of two human resource models for community-based active tuberculosis case finding in Ho Chi Minh City, Viet Nam

Table 4 Comparative ITS analysis model parameters of population-standardized quarterly notification rates of All Forms and bacteriologically-confirmed TB cases for control versus non-IMPACT-TB districts^a,b,c

	Control versus non-IMPACT-TB districts
	IRR^d	95% CI	p-value^e
All Forms TB
Baseline rate (β₀)	48.104	[47.315, 48.906]	< 0.001
Pre-intervention trend, control (β₁)	0.995	[0.994, 0.997]	< 0.001
Post-intervention step change, control (β₂)	0.795	[0.763, 0.829]	< 0.001
Post-intervention trend, control (β₃)	1.006	[0.997, 1.015]	0.168
Difference in baseline (β₄)	0.802	[0.785, 0.821]	< 0.001
Difference in pre-intervention trends (β₅)	1.006	[1.004, 1.008]	< 0.001
Difference in post-intervention step change (β₆)	1.012	[0.957, 1.071]	0.667
Difference in post-intervention trends (β₇)	1.006	[0.994, 1.018]	0.322
Bacteriologically-confirmed TB
Baseline rate (β₀)	27.461	[26.677, 28.268]	< 0.001
Pre-intervention trend, control (β₁)	1.001	[0.998, 1.003]	0.599
Post-intervention step change, control (β₂)	0.882	[0.825, 0.943]	< 0.001
Post-intervention trend, control (β₃)	1.006	[0.992, 1.020]	0.372
Difference in baseline (β₄)	0.810	[0.779, 0.843]	< 0.001
Difference in pre-intervention trends (β₅)	1.003	[1.000, 1.006]	0.053
Difference in post-intervention step change (β₆)	1.058	[0.968, 1.157]	0.217
Difference in post-intervention trends (β₇)	0.994	[0.976, 1.013]	0.553

^aThe parameters were obtained for a segmented regression model with the following structure: Y_t = β₀ + β₁T_t + β₂X_t + β₃X_tT_t + β₄Z + β₅ZT_t + β₆ZX_t + β₆ZX_tT_t + ϵ_t. Here Y_t is the outcome measure along time t; T_t is the monthly time counter; X_t indicates pre- and post-intervention periods, Z denotes the intervention cohort, and ZT_t, ZX_t, and ZX_tT_t are interaction terms. β₀ to β₃ relate to the control group as follows: β₀, intercept; β₁, pre-intervention trend; β₂, post-intervention step change; β₃, post-intervention trend. β₄ to β₇ represent differences between the control and intervention districts: β₄, difference in baseline intercepts; β₅, difference in pre-intervention trends; β₆, difference in post-intervention step changes; β₇, difference in post-intervention trend
^bThe baseline rate denotes case notification rates per quarter as monthly notification rates were unavailable for non-study districts
^cThe non-IMPACT-TB districts included eight of the 12 remaining districts in HCMC. Four districts were excluded due to concurrent ACF interventions (Go Vap, 7 and 10) and large differences in population growth (Nha Be)
^dIRR based on log-linear GEE Poisson regression with correlation structures as determined by the Cumby-Huizinga test and Quasi-Information Criteria
^eWald test

ISSN: 1471-2458