A RELIABLE METHOD TO RETRIEVE ACCIDENT AND EMERGENCY DATA STORED ON AFREE-TEXT BASIS

Accident & Emergency (A & E) data on asthma-related attendances are us eful for studies on the effectiveness of asthma interventions, and to determine the relationship of environmental factors to asthma and asth ma epidemics. The final dia gnoses made in the A & E departments are n ot usually coded when entered into hospital databases in the U.K., alt hough the 'presenting complaint' can be retrieved from the computerize d Hospital Information & Support Systems (HISS), from a free-text atte ndance diagnosis field entered by the reception clerk when the patient arrives at the A & E department, The validity of this as an indicatio n of the final diagnosis is unevaluated. The aim of this study was to measure the validity of the string 'asth' in the A & E attendance diag nosis field for identifying patients attending the A & E departments o f two hospitals for asthma-related conditions. A list of patients who attended the A & E department of two hospitals was retrieved from the HISS along with the attendance diagnosis field. If the attendance diag nosis field contained the text string 'asth', mentioned wheeze or brea thing problems, or the patients were referred by their GP without any diagnostic information entered on HISS, the records were selected for evaluation. The remaining attendances, which were not evaluated furthe r, were attributed to another diagnosis based on the evidence of the r ecorded attendance diagnosis. The results indicated that the string 'a sth' in the attendance diagnosis field had a sensitivity of 80.3% (95% CI 75.1-85.5%) and a specificity of 96.70% (95% CI 95.6-97.8%) for a final diagnosis of asthma. It is concluded that free-text attendance d iagnosis fields in hospital databases can be searched with suitable st rings to obtain reliable data on attendance with asthma. As part of an other investigation, the present authors attempted to retrieve a list of the attendances with asthma at the same two A & E departments at a time that was reportedly associated with an epidemic of asthma followi ng a thunderstorm. On this occasion, the string 'asth' proved to be si gnificantly less sensitive. The possible reasons for this and the impl ications for using this method for identifying cases are discussed.