The evaluation of rifampicin bioavailabilities of fixed-dose combinations of anti-tuberculosis drugs: procedures for ensuring laboratory proficiency.

Setting: The perceived need to demonstrate whether or not the rifampicin bioavailability of commercially manufactured fixed-dose combinations is satisfactory.

Objective: To establish an international laboratory network to assess rifampicin bioavailability.

Design: Convenient assay kits were devised to evaluate the ability of laboratories in China, India, Italy, South Africa, Thailand and the USA to determine plasma and urinary concentrations of rifampicin and desacetyl-rifampicin.

Results: Five laboratories, all of whom used high pressure liquid chromatographic methods, were shown to be able to accurately and precisely determine the two compounds.

Conclusion: Such a procedure is simple, convenient and objective and could be further employed to enlarge the intended international laboratory network.