Aeromonas species from non-chlorinated distribution systems and their competitive planktonic growth in drinking water.

Aeromonas is included in the Dutch Drinking Water Decree as an indicator for elevated microbial regrowth in non-chlorinated drinking water distribution systems (DWDS). The temporal and spatial diversity of Aeromonas species in ten DWDS and their planktonic growth characteristics for different carbon sources was investigated. Genotyping of the gyrB gene of isolates showed a non-systematic temporal and spatial variable prevalence of seven different Aeromonas species in these DWDS and no correlation with AOC-P17/NOX and Aeromonas concentrations. Pure cultures of these seven species showed a high affinity to low concentrations (µg/L) of individual amino acids and fatty acids, compounds associated with biomass. Growth occurred at 0.5 µg-C/L of an amino acid mixture. Growth of a mixed community of A. rivuli, A. salmonicida, A. sobria and A. veronii in drinking water occurred in pasteurized samples, however, no growth and decay occurred in competition with the autochthonous bacteria (non-pasteurized samples). This community also failed to grow in non-pasteurized distribution samples from a location with clear increase in planktonic Aeromonas concentrations in the transported drinking water. For competitive planktonic growth of Aeromonas an amino acid concentration of ≥5 µg-C/L is required. AOC-P17/NOX concentrations showed that such concentrations are not expected in Dutch drinking water. Therefore, we suspect that competitive planktonic growth is not the major cause of the observed non-compliance with the Aeromonas standard in non-chlorinated DWSD.Importance The occurrence of the bacterial genus Aeromonas in non-chlorinated drinking water in the Netherlands is regarded as an indication for elevated microbial regrowth in the distribution system. Identification of the prevalent species in ten distribution systems by genotyping yielded seven different species, with A. rivuli, A. veronii and A. sobria as the most dominant ones. Planktonic growth experiments of pure cultures confirmed former published affinity of Aeromonas for certain biomass compounds (amino and fatty acids). In competition with the autochthonous microflora, however, planktonic growth was not observed, only after addition of a threshold amino acid concentration of 5 µg-C/L. Based on our results and further observations we deduced that planktonic growth of Aeromonas in the DWDS is not very likely. Benthic growth in loose deposits and planktonic release is a more plausible explanation for the observed planktonic increase of Aeromonas.

Coiling of intracranial aneurysms: a systematic review on initial occlusion and reopening and retreatment rates.

BACKGROUND AND PURPOSE: The proportion of incompletely occluded aneurysms after coiling varies widely between studies. To assess overall outcome of coiling, we systematically reviewed the literature to determine initial occlusion, reopening, and retreatment rates of coiled aneurysms according to predefined criteria and subgroups. METHODS: We searched PubMed and EMBASE (January 1999 to September 2008) for studies of >50 coiled aneurysms. Two reviewers independently extracted data. We grouped studies reporting on only ruptured aneurysms, posterior circulation aneurysms, and studies with large proportions of aneurysms >10 mm to assess possible determinants for incomplete occlusion, reopening, and retreatment. RESULTS: Forty-six studies totalling 8161 coiled aneurysms met inclusion criteria. Immediately after coiling, 91.2% (95% CI, 90.6% to 91.9%) of the aneurysms were adequately occluded. Aneurysm reopening occurred in 20.8% (95% CI, 19.8% to 21.9%) and retreatment was performed in 10.3% (95% CI, 9.5% to 11.0%). Reopening rate was lower in studies reporting on ruptured aneurysms only compared with all studies (11.4% versus 20.8%; relative risk, 0.55; 95% CI, 0.47 to 0.64) and higher in studies focusing on posterior circulation aneurysms compared with studies with >85% anterior circulation aneurysms (22.5% versus 15.5%; relative risk, 1.5; 95% CI,1.2 to 1.7). Regression analysis showed higher retreatment rates with increasing proportion of aneurysms >10 mm (beta=0.252; 95% CI, 0.073 to 0.432). We could not find a relation between reopening and type of coils used. CONCLUSIONS: At follow-up, one fifth of all coiled intracranial aneurysms shows reopening of which half is retreated. Possible risk factors for aneurysm reopening are location in the posterior circulation and size >10 mm. To confirm our findings, a meta-analysis on individual well-reported patient data is desirable.

Interobserver variability in the detection of cerebral venous thrombosis using CT venography with matched mask bone elimination.

OBJECTIVES: Computed tomography venography (CTV) has proven to be a reliable imaging method in the evaluation of cerebral venous thrombosis with good correlation to magnetic resonance (MR) imaging and digital subtraction angiography (DSA). It is fast and widely accessible, especially in the emergency setting. For better visualization of vascular structures bone is often removed from the images. The purpose of this study was to evaluate the quality of a fully automatic bone removal method, matched mask bone elimination (MMBE), and to assess the interobserver variability of the CTV technique. PATIENTS AND METHODS: Fifty patients with clinical suspicion of cerebral venous thrombosis underwent multislice CTV with MMBE post-processing. Axial source images and maximum intensity projections were retrospectively evaluated by two neuroradiologists for quality of bone removal and for the presence or absence of thrombosis in nine dural sinuses and five deep cerebral veins. A per sinus/vein and a per patient analysis (thrombosis in at least one sinus or vein) was performed and interobserver agreement was assessed. RESULTS: Both observers considered bone removal good in all patients (100%). Interobserver agreement per patient was excellent (kappa=0.83), with a full agreement in 47 of 50 patients (94%). The interobserver agreement per sinus or vein was good (kappa=0.76), with a full agreement in 679 of 700 sinuses or veins (97%). CONCLUSION: CTV aided with MMBE is a robust technique for visualization of the intracranial venous circulation, removing bone effectively. CTV has high interobserver agreement for presence or absence of cerebral venous thrombosis.

Evidence of bias and variation in diagnostic accuracy studies.

BACKGROUND: Studies with methodologic shortcomings can overestimate the accuracy of a medical test. We sought to determine and compare the direction and magnitude of the effects of a number of potential sources of bias and variation in studies on estimates of diagnostic accuracy. METHODS: We identified meta-analyses of the diagnostic accuracy of tests through an electronic search of the databases MEDLINE, EMBASE, DARE and MEDION (1999-2002). We included meta-analyses with at least 10 primary studies without preselection based on design features. Pairs of reviewers independently extracted study characteristics and original data from the primary studies. We used a multivariable meta-epidemiologic regression model to investigate the direction and strength of the association between 15 study features on estimates of diagnostic accuracy. RESULTS: We selected 31 meta-analyses with 487 primary studies of test evaluations. Only 1 study had no design deficiencies. The quality of reporting was poor in most of the studies. We found significantly higher estimates of diagnostic accuracy in studies with nonconsecutive inclusion of patients (relative diagnostic odds ratio [RDOR] 1.5, 95% confidence interval [CI] 1.0-2.1) and retrospective data collection (RDOR 1.6, 95% CI 1.1-2.2). The estimates were highest in studies that had severe cases and healthy controls (RDOR 4.9, 95% CI 0.6-37.3). Studies that selected patients based on whether they had been referred for the index test, rather than on clinical symptoms, produced significantly lower estimates of diagnostic accuracy (RDOR 0.5, 95% CI 0.3-0.9). The variance between meta-analyses of the effect of design features was large to moderate for type of design (cohort v. case-control), the use of composite reference standards and the use of differential verification; the variance was close to zero for the other design features. INTERPRETATION: Shortcomings in study design can affect estimates of diagnostic accuracy, but the magnitude of the effect may vary from one situation to another. Design features and clinical characteristics of patient groups should be carefully considered by researchers when designing new studies and by readers when appraising the results of such studies. Unfortunately, incomplete reporting hampers the evaluation of potential sources of bias in diagnostic accuracy studies.

Polyp miss rate determined by tandem colonoscopy: a systematic review.

BACKGROUND AND AIMS: Colonoscopy is the best available method to detect and remove colonic polyps and therefore serves as the gold standard for less invasive tests such as virtual colonoscopy. Although gastroenterologists agree that colonoscopy is not infallible, there is no clarity on the numbers and rates of missed polyps. The purpose of this systematic review was to obtain summary estimates of the polyp miss rate as determined by tandem colonoscopy. METHODS: An extensive search was performed within PUBMED, EMBASE, and the Cochrane Library databases to identify studies in which patients had undergone two same-day colonoscopies with polypectomy. Random effects models based on the binomial distribution were used to calculate pooled estimates of miss rates. RESULTS: Six studies with a total of 465 patients could be included. The pooled miss rate for polyps of any size was 22% (95% CI: 19-26%; 370/1,650 polyps). Adenoma miss rate by size was, respectively, 2.1% (95% CI: 0.3-7.3%; 2/96 adenomas > or =10 mm), 13% (95% CI: 8.0-18%; 16/124 adenomas 5-10 mm), and 26% (95% CI: 27-35%; 151/587 adenomas 1-5 mm). Three studies reported data on nonadenomatous polyps: zero of eight nonadenomatous polyps > or =10 mm were missed (0%; 95% CI: 0-36.9%) and 83 of 384 nonadenomatous polyps <10 mm were missed (22%; 95% CI: 18-26%). CONCLUSIONS: Colonoscopy rarely misses polyps > or =10 mm, but the miss rate increases significantly in smaller sized polyps. The available evidence is based on a small number of studies with heterogeneous study designs and inclusion criteria.

Symptomatic and asymptomatic abnormalities in patients with lumbosacral radicular syndrome: Clinical examination compared with MRI.

OBJECTIVE: To determine the frequency of symptomatic and asymptomatic herniated discs and root compression in patients with lumbosacral radicular syndrome (LRS) and to correlate clinical localization with MRI findings. METHODS: Fifty-seven patients with unilateral LRS were included in the study. Using the visual analogue scale, two physicians independently localized the most likely lumbar level of complaints. These clinical predictions of localizations were correlated with the MRI findings. RESULTS: MRI showed abnormalities on the symptomatic side in 42 of 57 patients (74%). In 30% of the patients, MRI confirmed an abnormality at the exact same level as determined after clinical examination. On the asymptomatic side, MRI showed abnormalities in 19 of 57 patients (33%), 13 (23%) of these patients had asymptomatic root compression. CONCLUSIONS: In more than two-thirds of the patients with unilateral LRS there was no exact match between the level predicted by clinical examination and MRI findings. These discrepancies complicate the decision whether or not to operate.

MR angiography at 3T versus digital subtraction angiography in the follow-up of intracranial aneurysms treated with detachable coils.

BACKGROUND AND PURPOSE: Digital subtraction angiography (DSA) is used to follow-up intracranial aneurysms treated with detachable coils to identify recurrence and determine need for additional treatment. However, DSA is invasive and involves a small risk of neurologic complications. We assessed the feasibility and usefulness of 3D time-of-flight (TOF) MR angiography (MRA) performed at 3T compared with DSA for the follow-up of coil-treated intracranial aneurysms. METHODS: In a prospective study, 20 consecutive patients with 21 intracranial aneurysms treated with coils underwent DSA and nonenhanced and enhanced multiple overlapping thin-slab acquisition 3D TOF MRA at 3T on the same day at a mean follow-up of 6 months (range, 4-14 months) after coil placement. MRA images were evaluated for presence of artifacts, presence and size of aneurysm remnants and recurrences, patency of parent and branch vessels, and added value of contrast material enhancement. MRA and DSA findings were compared. RESULTS: Interobserver agreement of MRA was good, as was agreement between MRA and DSA. All three recurrences that needed additional treatment were detected with MRA. Minor disagreement occurred in four cases: three coil-treated aneurysms were scored on MRA images as having a small remnant, whereas on DSA images these aneurysms were occluded; the other aneurysm was scored on MRA images as having a small remnant, whereas on DSA images this was a small recurrence. Use of contrast material had no additional value. Coil-related MR imaging artifacts were minimal and did not interfere with evaluation of the occlusion status of the aneurysm. CONCLUSION: High-spatial-resolution 3D TOF MRA at 3T is feasible and useful in the follow-up of patients with intracranial aneurysms treated with coil placement.

Observer variation in MRI evaluation of patients suspected of lumbar disk herniation.

OBJECTIVE: Our objective was to assess observer variation in MRI evaluation in patients suspected of lumbar disk herniation. SUBJECTS AND METHODS: Two experienced neuroradiologists independently evaluated 59 consecutive patients with lumbosacral radicular pain. Per patient, three levels (L3-L4 through L5-S1) and the accompanying roots were evaluated on both sides. For each segment, the presence of a bulging disk or a herniation and compression of the root was reported. Images were interpreted twice: once before and once after disclosure of clinical information. Interobserver agreement was expressed as unweighted kappa values. RESULTS: Without clinical information, interobserver agreement for the presence of herniation or bulging disk was moderate (full agreement, 84%; kappa = 0.63; 95% confidence interval [CI], 0.53-0.72). Of a total of 352 segments evaluated, there was disagreement on 58 segments (17%): bulging disk versus no defect in 26 (7.4%), bulging disk versus herniation in five (1.4%), and hernia versus no defect in 27 (7.7%). With clinical information, twice as many bulging disks were reported but no new herniations were detected. Agreement slightly decreased, but not significantly (full agreement, 77%; kappa = 0.59; 95% CI, 0.49-0.69; p = 0.12). CONCLUSION: On average, more than 50% of interobserver variation in MRI evaluation of patients with lumbosacral radicular pain is caused by disagreement on bulging disks. Knowledge of clinical information does not influence the detection of herniations but lowers the threshold for reporting bulging disks.

CT colonography: feasibility of substantial dose reduction--comparison of medium to very low doses in identical patients.

In a feasibility study, the authors compared polyp detection and interobserver variability at computed tomographic (CT) colonography in 15 patients with doses ranging from medium to very low (12.00-0.05 mSv). At levels down to 2% of the medium dose, the mean detection of polyps 5 mm or larger remained at least 74%, while the number of false-positive results decreased and the interobserver agreement remained constant. Initial observations indicate that it is feasible to reduce the radiation dose required for CT colonography. Further studies are needed, however, to investigate the clinical value of very low-dose CT colonography.