OBJECTIVE: We aimed to identify the most accurate single-sample glomerular filtration rate (SS-GFR) technique for all patient ages.
METHODS: We performed a systematic review of all published SS-GFR measurement techniques and compared the results from each test with a gold-standard nine-point \'area-under-curve\' measurement of GFR as well as slope-intercept (SI-GFR) methods for 412 GFR tests.
RESULTS: We have shown that for patients of all ages the SS-GFR technique developed by Fleming and colleagues delivers the best accuracy and precision, with results equivalent to those calculated by SI-GFR. The median percentage difference from the gold-standard GFR for the Fleming technique is 4.8% (95% confidence interval 3.9-5.7%) and that for the three-point SI-GFR is 5.6% (95% confidence interval 4.9-6.3%). The interquartile range of the distribution of percentage difference from the gold standard is -0.23 to 11% for the Fleming method and 1.6-11% for the three-point SI-GFR.
CONCLUSIONS: The Fleming technique outperforms the method currently recommended by the international guidelines, and is simpler as only one equation is required for all patients instead of separate equations for adults and children. We propose that the SS-GFR technique of Fleming replace the methods currently recommended by the international and BNMS guidelines for routine measurement of GFR for expected results greater than 30 ml/min/1.73 m. A thorough system of measurement checks should be implemented for all methods of GFR assessment; the perceived lack of opportunity for quality control checks to be performed on the result of a single-sample measurement is addressed in the companion paper of this study.

Mercury is a toxic compound that can contaminate humans through food and especially via fish consumption. Mercury\'s toxicity depends on the species, with methylmercury being the most hazardous form for humans. Hg speciation analysis has been and remains a widely studied subject because of the potential difficulty of preserving the initial distribution of mercury species in the analysed sample. Accordingly, many analytical methods have been developed and most of them incur significant loss and/or cross-species transformations during sample preparation. Therefore, to monitor and correct artefact formations, quantification by isotope dilution is increasingly used and provides significant added value for analytical quality assurance and quality control. This review presents and discusses the two different modes of application of isotope dilution analysis for elemental speciation (i.e. species-unspecific isotope dilution analysis and species-specific isotope dilution analysis) and the different quantification techniques (i.e. classical and multiple spike isotope dilution analyses). Isotope tracers are thus used at different stages of sample preparation to determine the extent of inter-species transformations and correct such analytical artefacts. Finally, a synthesis of the principal methods used for mercury speciation in seafood using isotope dilution analysis is presented.

Graphical techniques provide simple methods for the analysis of data from tracer studies. They provide considerable ease of computation compared to the optimization of individual model parameters in the solution of the differential equations generally used to describe the binding of tracers. The theoretical work of Patlak which was applied to irreversible tracers formed the basis for extensions of graphical techniques to reversibly binding tracers. The advantage of graphical methods is that they are not dependent upon a particular model structure but provide a measure of tracer binding that can be interpreted in terms of a model structure if desired. They provide a visual way to distinguish the type of binding whether reversible or irreversible in the initial studies of new ligands. Conditions under which the graphical techniques can be applied are considered as well as problems encountered with slow binding components. One problem in the use of these methods particularly the method for reversible tracers is the bias generated due to the presence of statistical noise. Some recently proposed techniques for reducing the noise are considered.

Laboratory-based body-composition techniques include hydrostatic weighing (HW), dual-energy X-ray absorptiometry (DXA), measurement of total body water (TBW) by isotope dilution, measurement of total body potassium, and multicompartment models. Although these reference methods are used routinely, each has inherent practical limitations. Whole-body air-displacement plethysmography is a new practical alternative to these more traditional body-composition methods. We reviewed the principal findings from studies published between December 1995 and August 2001 that compared the BOD POD method (Life Measurement, Inc, Concord, CA) with reference methods and summarized factors contributing to the different study findings. The average of the study means indicates that the BOD POD and HW agree within 1% body fat (BF) for adults and children, whereas the BOD POD and DXA agree within 1% BF for adults and 2% BF for children. Few studies have compared the BOD POD with multicompartment models; those that have suggest a similar average underestimation of approximate 2-3% BF by both the BOD POD and HW. Individual variations between 2-compartment models compared with DXA and 4 -compartment models are partly attributable to deviations from the assumed chemical composition of the body. Wide variations among study means, -4.0% to 1.9% BF for BOD POD - HW and -3.0% to 1.7% BF for BOD POD - DXA, are likely due in part to differences in laboratory equipment, study design, and subject characteristics and in some cases to failure to follow the manufacturer\'s recommended protocol. Wide intersubject variations between methods are partly attributed to technical precision and biological error but to a large extent remain unexplained. On the basis of this review, future research goals are suggested.

This review focuses on the radioisotope methods used for studying the root activity patterns of woody perennials and root competition in multi-species cropping systems. 32P soil-injection is by far the most widely used method. The method is unique as it enables one to delineate the lateral and vertical spread of the absorbing roots. A system of classification of crop plants based on the concept of \'effective foraging space\' has been developed. The scope and applicability of the radioisotope methods in different cropping situations as well as from the point of view of radiological safety were discussed.

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