Analysis of time-to-positivity data in tuberculosis treatment studies: Identifying a new limit of quantification.

The BACTEC Mycobacteria Growth Indicator Tube (MGIT) machine is the standard globally for detecting viable mycobacteria in patients' sputum. Samples are observed for no longer than 42 days, at which point the sample is declared "negative" for tuberculosis (TB). This time to detection of bacterial growth, referred to as time-to-positivity (TTP), is increasingly of interest not solely as a diagnostic tool, but as a continuous biomarker wherein change in TTP over time can be used for comparing the bactericidal activity of different TB treatments. However, as a continuous measure, there are oddities in the distribution of TTP values observed, particularly at higher values. We explored whether there is evidence to suggest setting an upper limit of quantification (ULOQM) lower than the diagnostic limit of detection (LOD) using data from several TB-PACTS randomized clinical trials and PanACEA MAMS-TB. Across all trials, less than 7.1% of all weekly samples returned TTP measurements between 25 and 42 days. Further, the relative absolute prediction error (%) was highest in this range. When modeling with ULOQMs of 25 and 30 days, the precision in estimation improved for 23 of 25 regimen-level slopes as compared to models using the diagnostic LOD while also improving the discrimination between regimens based on Bayesian posteriors. While TTP measurements between 25 days and the diagnostic LOD may be important for diagnostic purposes, TTP values in this range may not contribute meaningfully to its use as a quantitative measure, particularly when assessing treatment response, and may lead to under-powered clinical trials.

A new technique for vascular access management in transcatheter aortic valve implantation.

OBJECTIVES: To describe results from a novel percutaneous technique designed to minimize the risk of hemorrhage in the event of a major complication during transcatheter aortic valve implantation. BACKGROUND: Vascular access management is a major challenge in transfemoral TAVI due to the large introducer sheathes required. METHODS: Fifty-two pts underwent TAVI between November 2007 and March 2009. Of these, 37 received an Edwards-Sapien Valve (23 mm valve: 17/37; 26 mm valve: 20/37) whilst 15 patients received a CoreValve (26 mm valve: 6/15; 29 mm valve: 9/15). Using a crossover technique, the opposing femoral artery was cannulated with a 7Fr long sheath. This allowed contralateral passage of a balloon and inflation in the proximal iliac. The sheath was then removed and Prostar sutures tied in a dry field. Balloon optimization of the puncture site was performed as required. RESULTS: In three subjects, elective surgical repair was undertaken due to excessive femoral arterial calcification. In the remaining 49, the crossover technique was employed and closed with two Prostar devices (Edwards-Sapien) or one (CoreValve). There were serious "on-table" complications in seven patients, six due to the large introducer sheathes used in the TAVI procedure-iliac avulsion, two iliac dissections, iliac perforation, common femoral perforation and scrotal hematoma. All were repaired safely by combined surgical and endovascular techniques, using the crossover technique to ensure patient stability. All made a good recovery and were independently ambulant at discharge. CONCLUSION: Using crossover balloon inflation as an adjunct to Prostar closure may be helpful for managing TAVI vascular access sites.