Bacterial contamination of QC specimens as a cause of artefactually poor performance in the UK EQAS.

During 1984-85, users of a solid-phase radioimmunoassay kit for LH and FSH had problems of both variability and bias in the assay of some EQAS specimens despite adequate internal QC. The cause has been identified as contamination of these specimens with Pseudomonas fluorescens.