PubMed · 13895650
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W A FUCHS. 1961-12-09. [Selective renal phlebography].. https://pubmed.ncbi.nlm.nih.gov/13895650/
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Screening and diagnostic tests are important in disease prevention or control. The predictive values of positive and negative (PPV and NPV) test results are two of four operational characteristics of a screening test. We review an existing method based on the generalized estimating equation (GEE) methodology for comparing predictive values from the same sample of subjects and propose two Wald test statistics derived from the weighted least squares (WLS) method for the analysis of categorical data. Using these results, we propose sample size calculation formulae for this problem. Simulation studies are conducted to compare the performances of the two Wald test statistics (one based on the difference of two PPVs or NPVs, another based on the logarithm of the ratio of two PPVs or NPVs) and the score/Wald test statistic derived from GEE. We recommend using the difference-based WLS approach.
Our objective was to evaluate restenosis after stenting of femoropopliteal occlusions and the impact of percutaneous transluminal angioplasty (PTA) on recurrent stenosis. We used a retrospective analysis of contrast angiograms obtained during follow-up of stented limbs. Subjects included 27 claudicants (34 limbs) who had complete superficial femoral artery occlusion treated with PTA and Wallstents at the Veterans Adminstration Medical Center. During follow-up, 31 PTAs, three thrombolytic treatments, and one additional stenting were performed. Outcome was measured by contrast angiography. Primary patency at 1 and 3 years was 38% and 8% after stenting, and secondary patency (PTA required at least once in 21/34 limbs) was 89% and 55%, respectively. PTA performed during follow-up reduced within-stent restenosis on average from 48.3 +/- 13.6% to 22.8 +/- 18.0%. Recurrent stenosis after PTA measured 14.9 +/- 10.9 months later was 46.8 +/- 16.7%, showing little permanent impact of PTA on stenosis. Severe within-stent stenosis develops commonly after initial stenting of complete femoropopliteal occlusions. Supplemental PTA performed during follow-up provides immediate improvement in lumen diameter, but severe restenosis is still likely to recur.
In compliance with institutional regulations for care and use of laboratory animals, the aim of this study was to establish and characterize a rodent liver tumor model to provide a platform for preclinical assessment of new diagnostic and therapeutic strategies. A rhabdomyosarcoma tumor was implanted in the right and left liver lobes of 20 rats, for a total of 40 tumors. T1- and T2-weighted magnetic resonance (MR) images, diffusion-weighted images, and dynamic susceptibility contrast agent-enhanced perfusion-weighted images were obtained up to 16 days after tumor implantation and were compared with postmortem three-dimensional computed tomographic (CT) images, digital microangiograms, and histopathologic findings. Fifteen tumors were examined with proton ((1)H) MR spectroscopy. All tumors grew, with a mean volume doubling time of 2.2 days +/- 0.9 (standard deviation) and a final size of 591 mm(3)+/- 124. The rhabdomyosarcoma tumor showed hypervascularity at MR imaging, three-dimensional CT, microangiography, and histologic analysis. On dynamic susceptibility contrast-enhanced perfusion-weighted images, the maximum signal intensity decrease differed in time and extent between the tumor and the liver, with a significantly (P < .001) higher relative blood volume, relative blood flow, and permeability value in the tumor than in the liver. With (1)H MR spectroscopy, the rhabdomyosarcoma tumor and the liver featured significant (P < .001) choline and lipid peaks, respectively. Implantation of a rhabdomyosarcoma tumor in the livers of rats is feasible and reproducible, and this animal model seems promising for future testing of new diagnostic and therapeutic strategies.