Correlation between drug concentrations (PK) and 
REGRESSION
There were significant simple linear correlations (all p values < 0.01) between all vaginal fluid PK concentrations and HIV inhibition by vaginal fluid (Spearman correlation coefficients for TFV, TAF and EVG versus percent HIV inhibition were 0.76, 0.78 and 0.81, respectively). Using multiple linear regression model (TAF + TFV or EVG), TFV in vaginal fluid remained significant (p < 0.01) and positively predictive of HIV inhibition. There was a significant interaction between vaginal fluid TFV and vaginal fluid EVG (p = 0.04) in multiple regression analysis, indicating both drugs contribute to the observed effect.In vaginal tissue, all PK concentration endpoints (TFV, TFV-DP, EVG and TAF) were significantly and negatively correlated with ectocervical HIV p24 antigen production (p24 area under the curve, p24 cumulative production and p24 at day 21 of tissue culture) with Spearman correlation coefficients ranging from -0.42 to -0.60 and all p values < 0.01.