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Appropriate coding systems for indexing clinical trials
62S
Abstracts abstract than in the full paper. Only rarely were the disagreement in results large, and it is not clear whether use of one result over another would affect a summary measure in a meaningful way. Conclusions Disagreements between data found in abstract and corresponding full publications occurred often. Though the differences in values were not large, those conducting meta analysis should contact original authors to confirm abstract data when there is no full publication.
45 APPROPRIATE CODING SYSTEMS FOR INDEXING CLINICAL TRIALS
W. Nigel Strang, Jean Maupas and Jean-Pierre Boissel Service de Pharmacologie Clinique Claude Bernard University Lyon, France Introduction: Evidence Based Medicine requires large data bases of trials which need to be indexed adequately. We consider that indexing terms fall into three categories: the Clinical Condition presented, the Interventions administered and the Outcomes measured. For the databases compiled by one group to be usable by another group, the terms and combinations of terms used in these categories need to be drawn from standard thesauri or coding systems. Methods: A survey of the literature concerning the availability of coding systems was carried out and choices were made concerning the systems to be adopted for each category of indexing term. A sample of clinical trials was drawn at random from the Cochrane Clinical Trials Register and attempts were made to attribute indexing terms from the coding systems. Results: UMLS, SNOMED, ICD10, MEDDRA, MESH, WHODRUG, GALEN and WHOART were initially retained for the experiment. The ultimate analysis is not yet available. However it is already clear that different coding systems are appropriate for different categories of information and for different disciplines. Discussion: Simple descriptions of well classified conditions and interventions are reasonably well covered by simple term based approaches, however there are conditions which are complex, treated by interventions that are complex to avoid or attain outcomes that are complex, and eventually it is unavoidable that terms will need to be combined according to the rules of an adequate description logic. Conclusion: Questions of coding go beyond Evidence Based Medicine and rejoin concerns of coding within clinical trials and electronic patient records. Currently in these fields simple coding standards are being adopted to resolve many problems, however some difficulties will remain until adequate connputer tractable description logics become available. As the registration of trials at inception becomes widespread such approaches will become essential in Evidence Based Medicine.
46 ISSUES IN COMPARISONS BETWEEN META-ANALYSES AND LARGE TRIALS
John P.A. Ioannidis, Joseph C. Cappelleri and Joseph Lau National Institute of Allergy and Infectious Diseases Bethesda, Maryland The extent of concordance between the results of meta-analyses and of large trials on the same topic has been investigated recently with different independent protocols (NEJM 1997;337:536-42, JAMA 1996;276:1332-38, Lancet 1995;345:772-6). Inconsistent conclusions have led to considerable confusion. We evaluated these protocols and compared their designs, study selection, methods of analysis, and frequency of observed disagreements between large trials and meta-analyses. The frequency of disagreements depends on whether
Abstracts abstract than in the full paper. Only rarely were the disagreement in results large, and it is not clear whether use of one result over another would affect a summary measure in a meaningful way. Conclusions Disagreements between data found in abstract and corresponding full publications occurred often. Though the differences in values were not large, those conducting meta analysis should contact original authors to confirm abstract data when there is no full publication.
45 APPROPRIATE CODING SYSTEMS FOR INDEXING CLINICAL TRIALS
W. Nigel Strang, Jean Maupas and Jean-Pierre Boissel Service de Pharmacologie Clinique Claude Bernard University Lyon, France Introduction: Evidence Based Medicine requires large data bases of trials which need to be indexed adequately. We consider that indexing terms fall into three categories: the Clinical Condition presented, the Interventions administered and the Outcomes measured. For the databases compiled by one group to be usable by another group, the terms and combinations of terms used in these categories need to be drawn from standard thesauri or coding systems. Methods: A survey of the literature concerning the availability of coding systems was carried out and choices were made concerning the systems to be adopted for each category of indexing term. A sample of clinical trials was drawn at random from the Cochrane Clinical Trials Register and attempts were made to attribute indexing terms from the coding systems. Results: UMLS, SNOMED, ICD10, MEDDRA, MESH, WHODRUG, GALEN and WHOART were initially retained for the experiment. The ultimate analysis is not yet available. However it is already clear that different coding systems are appropriate for different categories of information and for different disciplines. Discussion: Simple descriptions of well classified conditions and interventions are reasonably well covered by simple term based approaches, however there are conditions which are complex, treated by interventions that are complex to avoid or attain outcomes that are complex, and eventually it is unavoidable that terms will need to be combined according to the rules of an adequate description logic. Conclusion: Questions of coding go beyond Evidence Based Medicine and rejoin concerns of coding within clinical trials and electronic patient records. Currently in these fields simple coding standards are being adopted to resolve many problems, however some difficulties will remain until adequate connputer tractable description logics become available. As the registration of trials at inception becomes widespread such approaches will become essential in Evidence Based Medicine.
46 ISSUES IN COMPARISONS BETWEEN META-ANALYSES AND LARGE TRIALS
John P.A. Ioannidis, Joseph C. Cappelleri and Joseph Lau National Institute of Allergy and Infectious Diseases Bethesda, Maryland The extent of concordance between the results of meta-analyses and of large trials on the same topic has been investigated recently with different independent protocols (NEJM 1997;337:536-42, JAMA 1996;276:1332-38, Lancet 1995;345:772-6). Inconsistent conclusions have led to considerable confusion. We evaluated these protocols and compared their designs, study selection, methods of analysis, and frequency of observed disagreements between large trials and meta-analyses. The frequency of disagreements depends on whether