How to search for clinical trials on
the LILACS database using the internet
Numbers | Step-by-step | Webform | Search strategy | References | Contact


LILACS is the most complete and frequently updated (CD-ROM every four months: January, May and September; Internet every month) collection of databases for recording and disseminating the scientific production of Latin American and Caribbean Health professionals. It is the result of a cooperative effort between the constituent countries.

LILACS is an electronic database (CD-ROM and On-line) that indexes regional literature from more than 670 journals, with 270,244 (40th edition, May 2001) citations incorporated since 1982 with abstracts in are of English, Portuguese or Spanish. Of the 670 journals indexed in LILACS, only 41 overlap with MEDLINE/EMBASE. 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.

Using the Brazilian Cochrane Centre website ( you can have free access to the information on how to search the Lilacs database on-line: numbers of records, step-by-step instructions, webform, search strategy for RCTs, references and contact.

In the Cochrane Library 2000, Issue 2, of the 50 Cochrane Review Groups, only four are using the LILACS database (Depression, Anxiety & Neurosis; Hepato-biliary; Infectious Diseases; and Schizophrenia Groups). Just four others: Ear, Nose and Throat disorders; Metabolic and Endocrine Disorders; Neuromuscular Disease and Peripheral Vascular Disease Review Groups mention LILACS as an electronic Database that will be searched in the near future.

With each new edition of LILACS, the Brazilian Cochrane Centre will be locating new RCTs and CCTs for re-tagging Lilacs database and will send these for inclusion on the Cochrane Controlled Trials Register and CENTRAL.

LILACS at a glance!

Fields (31st edition,
May 1998)
(36th edition,
January 2000)
(37th edition,
May 2000)
(38th edition,
September 2000)
(39th edition,
January 2001)
(40th edition,
May 2001)
All records 188,061 233,709 242,538 250,816 261,865 270,244
Abstract available 114,173 (61%) 143,044 (61%) 148,573 (61%) 153,976 (61%) 161,021 (61%) 166,894 (61%)
Pt RCT 352 470 482 497 519 531
Pt CCT 48 168 186 192 277 250
Ct Human 116,660 143,385 148,462 152,867 158,751 163,044
La Spanish 103,900 130,249 135,081 139,322 145,156 150,008
La Portuguese 69,714 84,853 88,473 91,843 96,442 99,353
La English 15,157 19,562 20,032 20,814 21,694 23,383


First step - Construction of the search strategy
  • You must start by choosing one intervention or clinical situation. The strategy to find the RCTs is already done (Dickersin, 1994). The search strategy must be written using a specific sintax: it is identical to the notation used in logic mathematics. The use of parentheses follow the same rules, as in mathematical equations. The full strategy must be written in a single line, as a single search statement. This line is limited to up to 3000 characters. Truncation in the LILACS database is done using the "$" (dollar symbol).

Generic search strategy

(Cochrane search strategy for RCTs) AND (Intervention) AND (Clinical situation)

  • Search Field Qualification

    Terms can be qualified using LILACS Search Field tags. Input search (use operators OR, AND, AND NOT and prefix terms). Use one of the following prefixes below, if omitted, Tw will be assumed.
    Tw - Text words
    Ct - DeCS limits
    Au - Personal author
    Aa - Normalized personal author
    Ai - Institutional author
    Ti - Title words
    Ab - Abstract words
    La - Language
    Pd - Year publication
    Mh - Descriptors
    Ta - Journal
    Pt - Publication type
    Em - Entry month
    UI - Unique identifier

    Ex number$ - Exploding a MeSH term

    Creating and saving a search strategy: it is advisable to create the strategy using a word processing software, and if needed, save it there. The search strategy will be copied from the word processor in ASCII format and pasted in the advanced search form, using the first of the three available lines. The strategy statement used must contains Tags. When the strategy statement does not contain Tags, "Tw" will be used.

    The best policy is probably to start a search strategy by doing a preliminary search only for the intervention. Then do another search only for the clinical situation. If one or both give too many hits then combine the search strategies. If even after the combination there are still too many hits, the recommendation is to use the optimal search strategy, in addition.

Please note differences between formats on the first stage of the
Optimal Cochrane Collaboration Search strategy for RCTs

LILACS format

Pubmed format

Silver Platter (VERSION 3.10) format

(Pt randomized controlled trial OR Pt controlled clinical trial OR Mh randomized controlled trials OR Mh random allocation OR Mh double blind method OR Mh single blind method) AND NOT (Ct animal AND NOT (Ct human AND Ct animal))

(((((("Randomized Controlled Trial" [Publication Type] OR "Controlled Clinical Trial" [Publication Type]) OR "Randomized Controlled Trials" [MeSH Terms]) OR "Random Allocation" [MeSH Terms]) OR "Double Blind Method" [MeSH Terms]) OR "Single Blind Method" [MeSH Terms]) NOT ("Animal" [MeSH Terms] NOT ("Human" [MeSH Terms] AND "Animal" [MeSH Terms]))

#7 #1 or #2 or #3 or #4 or #5 or #6
#9 #7 not #8

· Upper case denotes controlled vocabulary.
· Lower case denotes free-text terms.


Second step - Copy search strategy and paste
  • Use the webform below, that was adapted to facilite the optimal search strategy for clinical trials, and will be soon available at Bireme website (Advanced search webform at Bireme website).
  • Line 1 - Paste the optimal search strategy
    Line 2 - Paste the search strategy for intervention
    Line 3 - Paste the search strategy for clinical situation
  • Note: the chraracters "[]" that comes out at the end of the search statement, in the results of the search, is due to a minor bug, that will be fixed soon. It does not interfere with the search or its results.

Attention: Use Mac or Pc Microsoft
Internet Explorer 4.01 or later

Local webform
Advanced search webform

Database: LILACS (Latin American and Caribbean Health Science Literature)
Edition: 40th, May 2001.

Advanced form adapted

    Search Strategy  



Optimal Search Strategy for Clinical Trials
(Bireme interface of the internet)

The strategy is divided into three stages: stage one (red words) includes terms with high precision, stage two (green words) includes terms with moderate precision, and stage three (blue words) includes terms with low precision but which provide optimal sensitivity.
[Copy all search strategy below and paste in first line of the form above]

((Pt randomized controlled trial OR Pt controlled clinical trial OR Mh randomized controlled trials OR Mh random allocation OR Mh double-blind method OR Mh single-blind method) AND NOT (Ct animal AND NOT (Ct human and Ct animal)) OR (Pt clinical trial OR Ex E05.318.760.535$ OR (Tw clin$ AND (Tw trial$ OR Tw ensa$ OR Tw estud$ OR Tw experim$ OR Tw investiga$)) OR ((Tw singl$ OR Tw simple$ OR Tw doubl$ OR Tw doble$ OR Tw duplo$ OR Tw trebl$ OR Tw trip$) AND (Tw blind$ OR Tw cego$ OR Tw ciego$ OR Tw mask$ OR Tw mascar$)) OR Mh placebos OR Tw placebo$ OR (Tw random$ OR Tw randon$ OR Tw casual$ OR Tw acaso$ OR Tw azar OR Tw aleator$) OR Mh research design) AND NOT (Ct animal AND NOT (Ct human and Ct animal)) OR (Ct comparative study OR Ex E05.337$ OR Mh follow-up studies OR Mh prospective studies OR Tw control$ OR Tw prospectiv$ OR Tw volunt$ OR Tw volunteer$) AND NOT (Ct animal AND NOT (Ct human and Ct animal)))


1) Castro AA, Clark OAC, Atallah AN. Optimal search strategy for clinical trials in the Latin American and Caribbean Health Science Literature Database (LILACS database): Update [Letter]. Sao Paulo Med J/Rev Paul Med 1999;117(3):138-9.

2) Castro AA, Clark OAC, Atallah AN. Optimal Search Strategy for Clinical Trials in the Latin American and Caribbean Health Science Literature Database (LILACS). Sao Paulo Med J/ Rev Paul Med 1997;115(5):1423-6. Medline Record

3) Dickersin K, Scherer R, Lefebvre C. Identifying relevant studies for systematic reviews. BMJ 1994;309:1286-9. Medline Record  

4) Clarke M, Oxman AD, editors. Optimal search strategy for RCTs. Cochrane Reviewers’ Handbook 4.0 [updated July 1999]; Appendix 5c. Section 4. In: Review Manager (RevMan) [Computer program]. Version 4.0. Oxford, England: The Cochrane Collaboration, 1999. From Dickersin K, Larson K. Establishing and maintaining an international register of RCTs. In: The Cochrane Library. Oxford: Update Software, 1996.

5) Castro AA, Atallah AN, Clark OA. .Locating and Appraising Systematic Reviews [letter, comment]. Ann Intern Med 1998;128(4):322-3. Comment on: Ann Intern Med 1998;126(7):532-8.  

6) Lowe HJ, Barnett GO. Understanding and using the Medical Subject Heandings (MeSH) vocabulary to perform literature searches. JAMA 1994;271(14):1103-1108. 

7) Soares K, Adams C. Searching non-Anglophone databases II: developing a search strategy for LILACS (abstract). Proceedings of the IV Cochrane Coloquium; 1996 Oct 15-19; Adelaide, Australian.



Comments, suggestions and criticisms will be welcome!
Send to: Aldemar Araujo Castro
Brazilian Cochrane Centre
Universidade Federal de São Paulo/Escola Paulista de Medicina
Rua Pedro de Toledo 598
04039-001 São Paulo, SP. Brazil.
Phone: (+55 11) 5575 2970
Fax: (+55 11) 5579 0469

HTML editor: Aldemar Araujo Castro
Last update: 20 June 2001 Next update: 20 December 2001