Inter-rater agreement in defining chemical incidents at the National Poisons Information Service, London.

BACKGROUND National surveillance for chemical incidents is being developed in the UK. It is important to improve the quality of information collected, standardise techniques, and train personnel. OBJECTIVE To define the extent to which eight National Poison Information Service specialists in poison information agree on the classification of calls received as "chemical incidents" based on the national definition. DESIGN Blinded, inter-rater reliability measured using the kappa statistic for multiple raters. SETTING National Poison Information Service and Chemical Incident Response Service, Guy's and St Thomas's NHS Trust, London. PARTICIPANTS Eight specialists in poison information who are trained and experienced in handling poisons information calls and have been involved in extracting information for surveillance. RESULTS The overall level of agreement observed was at least 69% greater than expected by chance (kappa statistic). Fire and incidents where chemicals were released within a property had a very good level of agreement with kappa statistic of 83% and 80% respectively. The lowest level of agreement was observed when no one or only one person was exposed to a chemical (33%) and when the chemical was released into the air (48%). CONCLUSION High levels of agreement were observed. There is a need for more training and improvement in consistency of the data collected by all organisations.