Statistical Identification Of Patient Selection Bias In Retrospective Chart Reviews

ABSTRACT:Purpose:To help investigators decide if new therapies for glioma warrant definitive evaluation in randomized studies we have been developing a method for assessing the degree to which patient selection may have enhanced the results of uncontrolled treatment trials. In this study, we analyzed the impact of case selection on the survival of patients with malignant glioma receiving adjuvant stereotactic radiosurgery, a promising therapy reserved for those with small tumors and good performance status.Methods:Following published eligibility criteria we simulated the patient selection process for stereotactic radiosurgery given as a boost at the conclusion of conventional radiotherapy. Eligible patients were culled from a pre-existing clinical/imaging database of 101 consecutive conventionally-treated patients with biopsy-proven malignant glioma and known survival times. Median durations of survival and 2- and 3-year survival rates were determined for those judged eligible or ineligible for stereotactic radiosurgery.Results:Twenty-seven percent of patients were deemed eligible for stereotactic radiosurgery, eligible patients had more favorable prognostic factors and significantly longer median survival than ineligible patients (23.4 vs. 8.6 months; 2-year rate, 48% vs. 15%; 3-year rate, 30% vs. 7%); eligible patients also had a longer median survival than the entire group of unselected patients (23.4 vs. 11.4 months). Radiosurgery-eligible, conventionally-treated patients with glioblastoma multiforme and a group of radiosurgery-treated patients at a special referral center had similar median survival times (16.4 vs. 19.7 months).Conclusion:We provide additional evidence for selection bias in uncontrolled trials of stereotactic radiosurgery and by simulating the selection process accurately have detected a larger bias effect than noted previously. Judging from experience with interstitial radiation and intraarterial chemotherapy where substantial selection bias also occurred and randomized controlled trials proved disappointing, we conclude that a phase III study of stereotactic radiosurgery for malignant glioma is unlikely to yield a positive result and may not be necessary.

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Acute Pulmonary Embolism: Impact of Selection Bias in Prospective Diagnostic Studies

Thrombosis and Haemostasis ◽

10.1055/s-0037-1615640 ◽

2001 ◽

Vol 85 (04) ◽

pp. 604-608 ◽

Cited By ~ 5

Author(s):

M.H. Prins ◽

H.R. Büller ◽

J.D. Banga ◽

I.J.C. Hartmann ◽

Keyword(s):

Pulmonary Embolism ◽

Selection Bias ◽

Acute Pulmonary Embolism ◽

Patient Characteristics ◽

Pulmonary Angiography ◽

Suspected Pulmonary Embolism ◽

Diagnostic Strategies ◽

A Prospective Study ◽

Diagnostic Technologies ◽

Patient Selection Bias

SummaryWe evaluated selection bias in a prospective study of 1162 consecutive patients with suspected pulmonary embolism. Of these, 983 were eligible, and 627 could actually be included. During two months extensive data were collected on all non-included patients. Finally, our patient characteristics were compared with those of the PIOPED study (1990) and the study of Hull et al. (1994). Compared with included patients, the non-included patients had more often non-diagnostic V/Q scans (50% vs. 36%, p <0.01) and were more often already hospitalized (31% vs. 22%, P = 0.04). The subgroup of patients not included due to refusal or inability to give informed consent (IC) was older (mean age 61 vs. 53 years, P <0.01), more often suffered from malignancies (26% vs. 11%, P <0.01) and frequently had non-diagnostic V/Q scans (57%) as compared to included patients. In our study, 54% of all patients screened was eventually included versus 27% in the PIOPED study. In the PIOPED study patients who had contra-indications for pulmonary angiography were excluded, while in the study of Hull et al. those with inadequate cardiorespiratory reserve were excluded. In studies on new diagnostic technologies, patient selection bias does occur. The potential for such a selection bias should be taken into account when diagnostic strategies are devised to improve their generalizability and acceptability.

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The removal and morphology of intact biofilms from implanted venous access devices

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100141470 ◽

1995 ◽

Vol 53 ◽

pp. 1020-1021

Author(s):

M.A. Gregory ◽

G.P. Hadley

Keyword(s):

Patient Selection ◽

Surgical Oncology ◽

Venous Access ◽

Common Procedure ◽

Indwelling Catheters ◽

Careful Patient ◽

Novel Method ◽

The Subject ◽

Vascular Catheters ◽

Venous Access Devices

The insertion of implanted venous access systems for children undergoing prolonged courses of chemotherapy has become a common procedure in pediatric surgical oncology. While not permanently implanted, the devices are expected to remain functional until cure of the primary disease is assured. Despite careful patient selection and standardised insertion and access techniques, some devices fail. The most commonly encountered problems are colonisation of the device with bacteria and catheter occlusion. Both of these difficulties relate to the development of a biofilm within the port and catheter. The morphology and evolution of biofilms in indwelling vascular catheters is the subject of ongoing investigation. To date, however, such investigations have been confined to the examination of fragments of biofilm scraped or sonicated from sections of catheter. This report describes a novel method for the extraction of intact biofilms from indwelling catheters.15 children with Wilm’s tumour and who had received venous implants were studied. Catheters were removed because of infection (n=6) or electively at the end of chemotherapy.

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