Quality control and data-handling in multicentre studies: the case of the Multicentre Project for Tuberculosis Research.

Background: The Multicentre Project for Tuberculosis Research (MPTR) was a clinical-epidemiological study on tuberculosis carried out in Spain from 1996 to 1998. In total, 96 centres scattered all over the country participated in the project, 19935 "possible cases" of tuberculosis were examined and 10053 finally included. Data-handling and quality control procedures implemented in the MPTR are described.

Methods: The study was divided in three phases: 1) preliminary phase, 2) field work 3) final phase. Quality control procedures during the three phases are described.

Results: Preliminary phase: a) organisation of the research team; b) design of epidemiological tools; training of researchers. Field work: a) data collection; b) data computerisation; c) data transmission; d) data cleaning; e) quality control audits; f) confidentiality. Final phase: a) final data cleaning; b) final analysis.

Conclusion: The undertaking of a multicentre project implies the need to work with a heterogeneous research team and yet at the same time attain a common goal by following a homogeneous methodology. This demands an additional effort on quality control.