Abstracts

SPECIAL ARTICLE

Optimal search strategy for clinical trials in the Latin American and Caribbean Health Science Literature Database (LILACS)

Aldemar Araujo Castro; Otávio Augusto Câmara Clark; Alvaro Nagib Atallah

Clinical Trial and Meta-Analysis Unit, Federal University of São Paulo, in conjunction with the Brazilian Cochrane Center - São Paulo, Brazil

^{Address for correspondence} Address for correspondence: Aldemar Araujo Castro Unidade de Ensaios Clínicos e Meta-Análise Universidade Federal de São Paulo Rua Pedro de Toledo, 598 São Paulo/SP - Brasil - CEP 04039-001

ABSTRACT

OBJECTIVE: To define and disseminate the optimal search strategy for clinical trials in the Latin American and Caribbean Health Science Literature (LILACS). This strategy was elaborated based on the optimal search strategy for MEDLINE recommended by Cochrane Collaboration for the identification of clinical trials in electronic databases.

DESIGN: Technical information.

SETTING: Clinical Trials and Meta-Analysis Unit, Federal University of São Paulo, in conjunction with the Brazilian Cochrane Center, São Paulo, Brazil. (http://www.epm.br/cochrane).

DATA: LILACS/CD-ROM (Latin American and Caribbean Health Science Information Database), 27th edition, January 1997, edited by BIREME (Latin American and Caribbean Health Science Information Center). LILACS Indexes 670 journals in the region, with abstracts in English, Portuguese or Spanish; only 41 overlap in the MEDLINE-EMBASE. Of the 168.902 citations since 1982, 104,016 are in human trials, and 38,261 citations are potentiality clinical trials. Search strategy was elaborated combining headings with text word in three languages, adapting the interface of the LILACS. We will be working by locating clinical trials in LILACS for Cochrane Controlled Trials Database. This effort is being coordinated by the Brazilian Cochrane Center.

Uniterms: Clinical Trial. Meta-Analysis. Electronic Databases. Location and Selecting studies. Information Storage and Retrieval. MEDLINE. LILACS.

RESUMO

OBJETIVO: Divulgar a estratégia otimizada de pesquisa de ensaios clínicos na base de dados Latino-Americana e do Caribe de Informações em Ciências da Saúde (LILACS). Ela foi elaborada baseada na estratégia recomendada pelo Cochrane Collaboration para identificação de ensaios clínicos no MEDLINE.

TIPO DE ESTUDO: Informe técnico.

LOCAL: Unidade de Ensaios Clínicos e Meta-Análise, Universidade Federal de São Paulo, em associação com o Centro Cochrane do Brasil, São Paulo, Brasil. (http:/ /www.epm.br/cochrane).

DADOS: A LILACS/CD-ROM (Base de dados Latino-Americana e do Caribe de Informações em Ciências da Saúde), 27º edição, janeiro/1997, é produzida pela BIREME (Centro Latino-Americano e do Caribe de Informações em Ciências da Saúde). Indexa 670 revistas da região, com resumos em inglês, português e espanhol; destas, 41 indexadas pelo MEDLINE-EMBASE. Possue 168.902 citações desde 1982, 104.016 são em humanos, 38.261 citações são potencialmente ensaios clínicos. A estratégia foi elaborada combinado descritores e palavras livres não três línguas, adaptando a interface da LILACS. Nós estaremos trabalhando para localizar ensaios clínicos no LILACS para a Base de Dados Cochrane de Ensaios Clínicos Controlados. Este esforço esta sendo coordenado pelo Centro Cochrane do Brasil.

INTRODUTION

An unbiased search is the key to a relevant systematic review. To protect against bias and ensure that all relevant data are included in a review, it is important to use multiple sources to identify studies and a systematic approach to select among them¹.

As for sources, Latin America and Caribbean have the LILACS², an electronic database (CD-ROM and On line) which indexes regional literature from more than 670 journals, with 168,904 citations incorporated since 1982 and abstracts in English, Portuguese or Spanish. The United States National Library of Medicine's medical subject headings (MeSH) vocabulary is used to index each LILACS citation. LILACS is edited by BIREME (Latin American and Caribbean Health Science Information Center), in the city of São Paulo, Brazil. Currently, BIREME is an agency of the Pan-American Health Organization / World Health Organization.

Of the 670 journals indexed in LILACS, only 41 overlap with MEDLINE-EMBASE². Therefore, the use, of LILACS for identifying clinical trials and systematic reviews should be a part of every search strategy. The Cochrane Schizophrenia Reviews Group (CSRG), in just one previous effort, identified 1,391 trials using LILACS alone³.

Our focus was to adapt the optimal search strategy for randomized controlled trials proposed by the Cochrane Collaboration by incorporating ideas from the CSRG to formulate the optimal search strategy for using LILACS.

OPTIMAL SEARCH STRATEGY FOR CLINICAL TRIALS

In Table 1 we present the optimal search strategy to be used with LILACS/CD-ROM, 27th edition, January 1997. The strategy is divided into the following three stages as defined in Dickersen⁴ et al. and replicated in the Cochrane Handbook: stage one (sets 1 - 9) includes terms with high precision; stage two (sets 10 - 28) includes terms with moderate precision; and stage three (sets 29 - 39) includes terms with low precision but with optimal browser sensitivity.

DISCUSSION

Using the optimal search strategy, are identifying 38,261 citations, in contrast with 3,505 citations retrieved by the CSRG have been identified search strategy. Only RCTs and CCTs will be selected from among these citations. Under the auspices of the Cochrane Collaboration, with each new edition of LILACS, we will be locating⁵ new RCTs and CCTs for the Cochrane Controlled Trials Register in the Cochrane Library.

In addition, we will be working retrospectively by locating clinical trials in old records of LILACS, through the CLINT-LAC PROJECT (Clinical Trials in the Latin American and Caribbean Project). This effort is being coordinated by the Brazilian Cochrane Center (http:// www.epm.br/cochrane).

At present, of the 31 Cochrane Reviews Groups, only the CSRG is using LILACS. Just two others, the Hepato-Biliary and Peripheral Vascular Disease Reviews Groups, mention LILACS as an electronic Database that will be searched in the near future. We observed this after verifying the search strategy of each group⁶.

As non-English-language references are under-represented in MEDLINE, and only published articles are included, there exists the potential for publication bias^4,7,10 and language bias^11,12. Thus, the inclusion of LILACS in any search strategy should be mandatory.

As for technology requirements, during installation of the DOS-based software for LILACS/CD-ROM, an interface for three languages is available, so that opting to use English for the search is easy. The principal difficulty is that saving the strategy to floppy disk is impossible. Only expert knowledge will resolve this problem.

An update of the search strategy could be necessary. The headings and free text search terms requiring evaluation are: CROSSOVER TRIAL, VERSUS, PROPHILATIC THERAPEUTIC TRAIL. It is fundamental to understand some important user principles¹³ in selecting MeSH or Non-MeSH terms for database searches.

The search strategy for questions concerning patients has three parts: disease, intervention, and study design¹⁴. Up to now, all discussion has been relevant only for the search strategy for locating study design; it has failed to consider the search strategy for identifying the disease and the intervention.

The search expression for locating clinical trials/ study design is: [(Disease AND Intervention) AND StudyDesign]. Analogously, it will be necessary to elaborate a search strategy for the disease and the intervention using headings and text free. The headings could verify the means, exploding if necessary. Text free (subject) will be synonyms, plural, different manner of writing, and correspondent words in English, Portuguese and Spanish languages will be indispensable. Obviously, further development is necessary in this area.

In conclusion, through constant efforts to elaborate and improve a search strategy for electronic databases, we are approaching the ideal. We believe that this collaborative work is the best way to reduce bias in locating and selecting clinical trials.

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