UK audit of glomerular filtration rate measurement in 2001.

OBJECTIVE: To investigate the consistency of glomerular filtration rate (GFR) calculation from plasma sampling in the UK. METHODS: Ten patients' data sets from plasma sampling measurements of GFR were distributed throughout the UK. The data included count rates from four samples taken between 2 and 4 h after injection, a diluted sample of injected dose for standardisation, the patient's height, weight, age and sex. Participants were asked to use the routine method to calculate GFR and express the results in absolute terms (i.e. in millilitres/minute) and normalized for body surface area (ml/min/1.73 m2). Supplementary data were also requested relating to workload, method used and normal range. Intercentre variability was assessed by calculating the root median square (RMedS) deviation of each GFR from the median for that data set. Centres using a particular analysis method were grouped together and the RMedS deviation of each result from the median for that group and that data set was calculated. The influence of using normalized data and number of samples was also studied. RESULTS: Seventy-nine returns were received. For the normalized data, the overall RMedS variability was 5.8 ml/min/1.73 m2. This decreased significantly to 0.6 ml/min/1.73 m2 when results were grouped by analysis method. Results were similar for non-normalized data. A small but significant decrease in error with the number of samples was observed. CONCLUSION: Considerable variability in GFR values obtained at different centres in the UK for a given set of data was observed. Nearly all this variability was due to different methods of analysis. If methodology were standardized then intercentre variability in GFR analysis could be reduced dramatically. Radionuclide techniques are confirmed as being the method of choice if an accurate value of GFR is required.

Behavioral phenotyping and dopamine dynamics in mice with conditional deletion of the glutamate transporter GLT-1 in neurons: resistance to the acute locomotor effects of amphetamine.

RATIONALE: GLT-1 is the major glutamate transporter in the brain and is expressed predominantly in astrocytes but is also present in excitatory axon terminals. To understand the functional significance of GLT-1 expressed in neurons, we generated a conditional GLT-1 knockout mouse and inactivated GLT-1 in neurons using Cre-recombinase expressed under the synapsin 1 promoter, (synGLT-1 KO). OBJECTIVES: Abnormalities of glutamate homeostasis have been shown to affect hippocampal-related behaviors including learning and memory as well as responses to drugs of abuse. Here, we asked whether deletion of GLT-1 specifically from neurons would affect behaviors that assessed locomotor activity, cognitive function, sensorimotor gating, social interaction, as well as amphetamine-stimulated locomotor activity. METHODS/RESULTS: We found that the neuronal GLT-1 KO mice performed similarly to littermate controls in the behavioral tests we studied. Although performance in open field testing was normal, the acute locomotor response to amphetamine was significantly blunted in the synGLT-1 KO (40% of control). We found no change in amphetamine-stimulated extracellular dopamine in the medial shell of the nucleus accumbens, no change in electrically stimulated or amphetamine-induced dopamine release, and no change in dopamine tissue content. CONCLUSIONS: These results support the view that GLT-1 expression in neurons is required for amphetamine-induced behavioral activation, and suggest that this phenotype is not produced through a change in dopamine uptake or release. Although GLT-1 is highly expressed in neurons in the CA3 region of the hippocampus, the tests used in this study were not able to detect a behavioral phenotype referable to hippocampal dysfunction.

UK audit of left ventricular ejection fraction estimation from equilibrium ECG gated blood pool images.

PURPOSE: To examine the variability of results obtained from computer analysis of left ventricular gated blood pool (LVGBP) images by nuclear medicine centres in the UK. METHODS: Twelve data sets of LVGBP images were distributed via commercial software suppliers to nuclear medicine centres in the UK. Two of the data sets were duplicates and three were acquired from the same patient with different total counts in the images. The quality of the images was also variable and two images had poorly defined left ventricular walls. A questionnaire was used to identify the parameters used during the analysis and to give an indication of the number of LVGBP scans per year routinely carried out by each centre as well as report the results obtained from the analysis. RESULTS: Results were received from 63 nuclear medicine centres using 77 computer systems. The vast majority of participants (57) carried out fewer than 10 scans per month. Only two centres performed more than 30 scans per month. Sixteen centres did not quote a minimum normal value for left ventricular ejection fraction (LVEF) and 36 did not record a maximum value. The remainder recorded between 0.40 and 0.60 for the minimum of normal range and 0.60-0.90 for the maximum of normal range. Analysis of returns showed that LVEF estimates for the data sets were highly variable between centres and computer systems. The overall standard deviation of results compared to the mean for each study was 0.076. Approximately half this variation was due to systematic variation between centres. The overall precision taking into consideration this systematic variation, was 0.055. Lower variability was found between studies with higher overall counts and this was highly significant.

UK audit of relative lung function measurement from planar radionuclide imaging.

BACKGROUND: Quantitative measurements of regional lung ventilation and perfusion are useful adjuncts to image interpretation. AIM: This study investigated the accuracy and precision of the software used to carry out such measurements in the UK. METHODS: Ten examples of perfusion distribution, representing the range of patterns expected in practice, were simulated on computer using a segmental model of the lung and real three-dimensional lung shapes obtained from magnetic resonance images. Pairs of anterior and posterior perfusion images were simulated and distributed to UK hospitals wishing to take part in the audit. Each centre returned analysis results and technical details. Forty centres provided data on the relative right:left lung perfusion. Thirteen also submitted data with each lung divided into three zones and four with each lung divided into two zones. All measurements were expressed by the percentage of total perfusion in a particular region. Errors were assessed as the root-mean-square (rms) deviation from the true value. RESULTS: Methods varied in the view used for analysis (80% geometric mean, 20% posterior) and the use of background subtraction (71% not used, 29% used). The rms error for percentage right assessment was 1.5 percentage points. This increased on two- and three-zone analysis to 3.8 and 4.3 percentage points, respectively. Differences in technique made little difference to whole-lung relative perfusion errors, but were important in zonal analysis. CONCLUSIONS: Quantification of whole-lung relative function is accurate and reproducible. Zonal values are determined less accurately, but still provide a useful guide to the distribution of function.

UK audit of analysis of quantitative parameters from renography data generated using a physical phantom.

BACKGROUND: In this second UK audit of quantitative parameters obtained from renography, phantom simulations were used in cases in which the 'true' values could be estimated, allowing the accuracy of the parameters measured to be assessed. MATERIALS AND METHODS: A renal physical phantom was used to generate a set of three phantom simulations (six kidney functions) acquired on three different gamma camera systems. A total of nine phantom simulations and three real patient studies were distributed to UK hospitals participating in the audit. Centres were asked to provide results for the following parameters: relative function and time-to-peak (whole kidney and cortical region). As with previous audits, a questionnaire collated information on methodology. Errors were assessed as the root mean square deviation from the true value. RESULTS: Sixty-one centres responded to the audit, with some hospitals providing multiple sets of results. Twenty-one centres provided a complete set of parameter measurements. Relative function and time-to-peak showed a reasonable degree of accuracy and precision in most UK centres. The overall average root mean squared deviation of the results for (i) the time-to-peak measurement for the whole kidney and (ii) the relative function measurement from the true value was 7.7 and 4.5%, respectively. These results showed a measure of consistency in the relative function and time-to-peak that was similar to the results reported in a previous renogram audit by our group. CONCLUSION: Analysis of audit data suggests a reasonable degree of accuracy in the quantification of renography function using relative function and time-to-peak measurements. However, it is reasonable to conclude that the objectives of the audit could not be fully realized because of the limitations of the mechanical phantom in providing true values for renal parameters.