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Table 3 Structural equation modelling and mediation analysis to estimate the contribution of infant HIV exposure and ART score to %MTCT and the paediatric case rate

From: What will it take for the Global Plan priority countries in Sub-Saharan Africa to eliminate mother-to-child transmission of HIV?

Main outcome: %MTCT
a) Structural equation model
  Path Coef (95%CI) Standardized coef p-value
 Direct effects HEI → % MTCT 0.11 (-0.15, 0.37) 0.15 0.398
ART_score → % MTCT -0.11 (-0.15, 0.08) -0.85 <0.001
HEI → ART_score 3.64 (2.27, 5.02) 0.63 <0.001
Indirect (mediation) effectb HEI → % MTCT -0.41 (-0.61, -0.21) -0.54 <0.001
Total effects HEI → % MTCT -0.30 (-0.54, -0.05) -0.39 0.018
ART_score → % MTCT -0.11 (-0.15, -0.08) -0.85 <0.001
HEI → ART_score 3.65 (2.27, 5.02) 0.63 <0.001
b) Linear Regression model
 Model independent variable outcome Coef (95% CI) Standardized coef. (Adjusted R2) p-value
 Simple linear HEI % MTCT -0.27 (-0.58, 0.04) -0.35 (0.08)* 0.089
ART_score % MTCT -0.10 (-0.14, -0.06) -0.74 (0.53)* <0.001
HEI ART_score 3.39 (1.41, 5.36) 0.60 (0.34)* 0.002
 Multiple regression HEI
ART_score
% MTCT 0.11 (-0.17, 0.40) 0.15.a 0.418
%MTCT -0.11 (-0.16, -0.06) -0.85 (0.53a <0.001
Mediated effectsb HEI % MTCT -0.38 (-0.64, -0.21)   <0.001
Main Outcome: Paediatric case rate (case-rate)
a) Structural equation model
Effect Path Coef (95%CI) Standardized coef p-value
 Direct effects HEI → Case_rate 82.2 (66.1,98.3) 1.03 <0.001
ART_score → Case_rate -2.9 (-5.7, -0.01) -0.21 0.05
HEI → ART_score 3.7 (2.0, 5.5) 0.64 <0.001
Indirect (mediation) effectb HEI → Case_rate -10.6 (-22.4, 1.2) -0.13 0.077
Total effects HEI → Case_rate 71.6 (57.9, 85.3) 0.90 <0.001
ART_score → Case_rate -2.9 (-5.7, -0.01) -0.21 0.05
HEI → ART_score 3.73 (2.0, 5.5) 0.64 <0.001
b) Linear Regression model
 Model predictor outcome Coef (95% CI) Standardized coef. (Adjusted R2) p-value
 Simple linear HEI Case_rate 72.8 (57.5, 88.2) 0.90 (0.81)* <0.001
ART_score Case_rate 6.1 (0.92, 11.4) 0.45 (0.17)* 0.023
HEI ART_score 3.4 (1.4, 5.4) 0.60 (0.34)* 0.002
 Multiple regression HEI Case_rate 82.8 (64.6, 101.1) 1.03 (0.83a) <0.001
ART_score Case rate -3.0 (-6.2, 0.31) -0.20 0.074
Mediated effectsb HEI Case_rate -10.0 (-21.8, 1.8)   >0.05
  1. HEI=Infant HIV exposure, case-rate= number of new paediatric HIV infections per 100 000 live births (paediatric HIV case rate), %MTCT= percent mother to child transmission of HIV, ART-score=% of HIV on treatment + % HIV-suppressed + % of pregnant women on ART.
  2. a: Adjusted R2 for full multiple regression model b indicated mediated effects   *indicates proportion of outcome (out of 1) explained by this variable in simple linear regression