Sensitivity and specificity of faecal tumour M2 pyruvate kinase for detection of colorectal adenomas in a large screening study

The measurement of faecal tumour M2 pyruvate kinase (tumour M2 PK) has been proposed as a novel approach for early detection of colorectal cancer (CRC). However, as regards the potential of the test to detect precursors to CRC, an issue that is highly relevant to estimate its use in reducing CRC incidence and mortality, the available evidence is scant and controversial. The aim of our study was to determine the performance characteristics of the tumour M2 PK test with respect to colorectal adenomas in the target population of screening. Among 1082 participants of screening colonoscopy in Germany, of whom 30% had any adenoma and 10% had an advanced adenoma, the median (interquartile range) tumour M2 PK level in the whole study population was 1.3 U ml−1 (0.3–3.3). At a cutoff value of 4 U ml−1, sensitivity was 22 and 23% for detection of advanced and other adenomas, respectively, whereas specificity was 82%. The area under the receiver-operating characteristics curve (95% confidence interval) was 0.54 (0.51–0.58) and 0.56 (0.52–0.59) for advanced and other adenomas, respectively. In conclusion, the tumour M2 PK test has only very limited potential to distinguish between people bearing precursors to CRC and people with no finding at colonoscopy

High-temperature redox chemistry of Pr0.5Sr1.5Cr0.5Mn0.5O4-delta investigated in situ by neutron diffraction and X-ray absorption spectroscopy under reducing and oxidizing gas flows

The structural and redox stability of the n = 1 Ruddlesden-Popper (RP) oxide Pr 0.5Sr 1.5Cr 0.5Mn 0.5O 4-δ, synthesized by the citrate-gel method, has been investigated over the temperature range 25-700 °C under reducing (5% H 2 flow) and oxidizing (O 2 or air flow) conditions by means of in situ neutron powder diffraction (NPD) and X-ray absorption near-edge structure spectroscopy (XANES). Sequential Rietveld refinement of the NPD patterns collected under hydrogen revealed de-intercalation of oxide ions from the equatorial anion positions with retention of I4/mmm symmetry. The reduction from Pr 0.5Sr 1.5Cr 0.5Mn 0.5O 4.00(2) to Pr 0.5Sr 1.5Cr 0.5Mn 0.5O 3.81(2) is accompanied by an expansion of both the a and c lattice parameters. When the reduced sample is heated in air, oxygen refills the equatorial sites and the unit cell contracts; the interlayer interstitial site remains unoccupied. XANES showed the oxidation states in the as-prepared composition to be Pr 3+, Cr 3+ and Mn 4+. When the material is heated under dilute hydrogen, the oxidation states Pr 3+ and Cr 3+ are retained whereas Mn 4+ is reduced to Mn 3+. These observations constitute the first direct evidence that the d-block element, and not praseodymium, is responsible for the electrocatalytic activity of Pr-containing RP oxides. When the reduced material is heated under oxygen, Mn 3+ is reoxidised to Mn 4+ and a low concentration of tetrahedrally-coordinated Cr(vi) forms, suggesting a possible poisoning mechanism in fuel-cell applications. © The Royal Society of Chemistry 2012