 In addition to the parent trial, the investigators will include an additional component called the Biomarker Study. For this part of the study the investigators will take an additional 10 mls of blood pre-treatment, as well as at four and nine months after starting treatment. In total an extra 30ml of blood equal to 2 tablespoons will be required over 9 months, and two additional veni-punctures, since veni-punctures will not be routinely performed at the 4 and 9 month time points. Three of the 10 ml will be used for the QFT-GIT test, the remaining 7 ml will have the serum separated and stored at -80C for future biomarker studies. For subjects who were randomized to 4RIF, the blood draw at nine months will require an extra visit to the clinic, for which study subjects will be compensated. No specimens will be stored for future genetic testing. For the present time only the Montreal site will participate in this component. Other sites will join once funding is secured. All lab assays will be performed in the final year of the study, to enhance cost-effectiveness. 