Best Evidence Topics

Survey (including pre-test probabilities)

Scott DA, Silbert BS, Blyth C, O'Brien J, Santamaria J.
Blood loss in elective coronary artery surgery: a comparison of centrifugal versus roller pump heads during cardiopulmonary bypass.
J Cardiothorac Vasc Anesth
2001; 15:322325.
  • Submitted by:Jenifer Barrie - Student
  • Institution:University of Manchester
  • Date submitted:7th July 2005
Before CA, i rated this paper: 5/10
1 Objectives and hypotheses
1.1 Are the objectives of the study clearly stated?
  Yes, in the abstract and introduction vaguely. Specific variables were described in the methods.
2 Design
2.1 Is the study design suitable for the objectives
2.2 Who / what was studied?
  1427 heroin injectors from 6 innercity neighbourhoods in the San Francisco bay area.
Study sought to determine prevalence and risk factors of non fatal overdose.
2.3 Was this the right sample to answer the objectives?
  yes, all had recently injected heroin
2.4 Did the subject represent the full spectrum of the population of interest?
  Only injectors were studied,excluding other users. They are only from the San Francisco bay area.
2.5 Is the study large enough to achieve its objectives? Have sample size estimates been performed?
  The sample size is very large but sample size estimates were not performed.
2.6 Were all subjects accounted for?
  The totals in table 1 come to less than 1427 in 7 out of the 9 categories.
The numbers also do not add up in table two
2.7 Were all appropriate outcomes considered?
  Use of sedatives was considered but not the amount.
All other outcomes were considered.
2.8 Has ethical approval been obtained if appropriate?
  The study was approved by the University of California, San Francisco, Committee on Human Research, participants gave informed consent.
2.9 What measures were made to contact non-responders?
  Participants were interviewed by trained counsellors in person.
2.10 What was the response rate?
3 Measurement and observation
3.1 Is it clear what was measured, how it was measured and what the outcomes were?
  Age of study participants measured in years, median was 44 years.
Subjects decribed their race, sex, sexual orientation, place of dwelling or if homeless,time spent in prison, frequency of arrest, participant in treatment and injection behaviour according to appropriate category specified.
3.2 Are the measurements valid?
3.3 Are the measurements reliable?
  Relied on subjects honesty and accuracy about overdose.
3.4 Are the measurements reproducible?
  Yes, the survey could be carried out in any group.
4 Presentation of results
4.1 Are the basic data adequately described?
  Yes in the results section mainly as percentages and risk factors were described.
4.2 Are the results presented clearly, objectively and in sufficient detail to enable readers to make their own judgement?
  Yes there are three tables presenting all data found with basic numerical values, percentages and confidence intervals.
4.3 Are the results internally consistent, i.e. do the numbers add up properly?
  Some totals in the table don't add up.
5 Analysis
5.1 Are the data suitable for analysis?
5.2 Are the methods appropriate to the data?
  Factors hypothesized to be associated with recent overdose were analysed by logistic regression.
5.3 Are any statistics correctly performed and interpreted?
  Yes but some odds ratios were small.
6 Discussion
6.1 Are the results discussed in relation to existing knowledge on the subject and study objectives?
  Yes results are compared to recents studies which are referenced.
6.2 Is the discussion biased?
  No studies are mentioned that have confounding results but these may not exist. The discussion did, however, talk about the papers shortcomings.
6.3 Can the results be generalised?
  No, as this was not a true random sample.
7 Interpretation
7.1 Are the authors' conclusions justified by the data?
  Yes conclusion discusses how risk factors with the highest odds ratios must be targeted. for prevention.
7.2 What level of evidence has this paper presented? (using CEBM levels)
  Level 2.
7.3 Does this paper help me answer my problem?
  Yes, it discusses the factors associated with non fatal overdose and which have a higher odds ratio.
After CA, i rated this paper: 7/10
8 Implementation
8.1 Can any necessary change be implemented in practice?
  Yes, focusing on prevention of overdose in those frequently arrested, who drink alcohol daily and have been in methadone detoxification.
8.2 What aids to implementation exist?
  Health professionals involved in methadone detoxification could educate patients on the risks and monitor treatment carefully.
Police and probation officers could be made aware of dangers.
Health professionals should be made aware of concomitant use of alcohol and drug and alcohol detox programmes made more readily available.
Safe injection rooms and resuscitation training could be implemented.
8.3 What barriers to implementation exist?
  Some addicts are not in contact with health professionals regularly.
The use of take home naloxone must be piloted before the strategy can be widely implimented.
More money and resources are needed for opiate and alcohol detox programmes together and workers may need further training which takes time.