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Negative Study (negative + study)

Distribution by Scientific Domains

Medical Sciences	100%

Selected Abstracts

Publication bias perpetuates use of ineffective drugs in stroke

INTERNATIONAL JOURNAL OF STROKE, Issue 3 2009
K. Prasad
Drugs approved and used for treatment of stroke vary from country to country. This is, at least, partly because of variation in the standards of evidence that is required for approval of drugs across countries. For example, some countries, usually low and middle income ones, approve a drug on the basis of a small positive study or post hoc subgroup analysis in a overall negative study, while others, usually high income countries, require confirmatory or replication studies before approving the same drug. Needless to say that such confirmatory or replication studies need to be published and adequately disseminated as soon as possible so that approval decisions can be revised in the light of additional evidence. However, this does not always happen. The new evidence often remains hidden in the form of nonpublication or abbreviated publication. Sometimes, it is published but with undue delay. What is worrisome is that these problems occur more often when the new evidence does not favor the new drugs than when it favors them, a manifestation of what is called ,publication bias.' This bias is well documented in the stroke research literature (1, 2). [source]

Publishing the nuisance negative study

JOURNAL OF COSMETIC DERMATOLOGY, Issue 1 2008
Zoe Diana Draelos MD
[source]

Assessment of referral patterns for CT KUB in a tertiary setting

JOURNAL OF MEDICAL IMAGING AND RADIATION ONCOLOGY, Issue 6 2009
H Jo
Summary The purpose of this study was to assess the referral patterns and the use of unenhanced renal tract CT (CT KUB) for investigating patients presenting with clinically suspected renal colic. We retrospectively reviewed 500 consecutive CT KUB studies requested for suspected renal colic carried out at a single institution between December 2006 and July 2007. Follow-up radiology reports and discharge summaries on the hospital clinical Intranet were also reviewed. Studies were analysed for characteristics including patient demographics, referring clinical team, time of referral, final diagnosis and requirement for further imaging. The majority of requests were from Emergency (ED) or Urology Departments (49%, 245 out of 500, and 37%, 186 out of 500, respectively). The positive rate for urolithiasis was 67% (337 out of 500), the negative rate was 25% (123 out of 500), and 8% (40 out of 500) of patients had alternative significant findings. Female patients were more likely to have a negative study than male patients (35 versus 20%, P < 0.0001) and more likely to have alternative significant pathology (12 versus 6%, P < 0.0001). Patients referred by specialities other than Urology and ED were more likely to be female and have a negative or alternative finding (P < 0.0001). CT KUB is a widely used first method of investigation for patients with suspected renal colic with a high positive predictive value allowing rapid diagnosis and intervention. However, given the high rate of negative or alternative findings on CT KUB in young women, especially those referred by specialities other than ED or Urology, ultrasound should be considered as an alternative imaging method to minimise unnecessary radiation exposure. [source]

The role of indirect radionuclide cystography during the acute phase of pyelonephritis in young women

BJU INTERNATIONAL, Issue 4 2005
Jehonathan H. Pinthus
Authors from Israel have investigated the use of dynamic renal scans in young female patients with acute pyelonephritis, combined with indirect radionuclide cystography. They found that using these techniques may avoid up to half of the delayed voiding cysto-urethrograms, preventing the related inconvenience and cost. OBJECTIVE To review our experience using dynamic 99mTc-diethylenetriamine penta-acetic acid renal scintigraphy combined with indirect radionuclide cystography (IRC) in the acute phase of pyelonephritis, as a possible alternative to the conventional imaging, as investigating acute pyelonephritis usually includes imaging the upper urinary tract during the acute phase, to exclude obstruction, and delayed voiding cysto-urethrography (VCUG) when underlying vesico-ureteric reflux (VUR) is suspected. PATIENTS AND METHODS Between 1997 and 1999, 47 young women (median age 22 years, range 18,37) were hospitalized for acute pyelonephritis. The combined study was used during the acute phase of the disease, usually within 24 h of hospitalization. The principle of IRC is based on the reappearance of radioactivity in the ureters or kidneys after previously detecting renal clearance of an intravenously injected radioisotope. The increase in radioactivity over the ureters or kidneys indicates VUR. The subsequent follow-up included VCUG, after recovery and at least 6 weeks after discharge. RESULTS Overall, 47 patients had early IRC studies; obstruction of the urinary tract during the acute phase of the disease was excluded in all. In 13 (28%) of the patients early IRC studies showed VUR involving 21 upper tract units. The renal parenchymal scan was impaired in 17 (36%) patients, and six of these 17 also had detectable concomitant reflux on IRC. Overall, 24 IRC studies (51%) were considered positive, showing VUR, renal parenchymal pathology or both; 23 (49%) were normal. Follow-up VCUG was used in 32 patients (68%); only three (9%) detected VUR. All of the patients with VUR on follow-up VCUG had also had an abnormal early IRC study, showing either reflux (two) or findings suggestive of pathological renal parenchyma (one). CONCLUSIONS In addition to the well-established role of renal scintigraphy in excluding obstruction of the collecting system, early IRC is characterized by high sensitivity and accurate negative predictive value for detecting VUR. It can therefore be used to screen adults presenting with acute pyelonephritis for the presence of VUR. Patients with an abnormal IRC require follow-up VCUG after complete recovery, while those with a negative study may be managed expectantly, with no further radiological evaluation. This proposed strategy may avoid up to half of the delayed VCUG studies, preclude the related inconvenience, and substantially reduce the costs. [source]