The importance of developmental field trials in the revision of psychiatric classifications.

Field trials of diagnostic classification systems can be divided into two types: developmental field trials, which are designed to collect performance data from users during the revision process, and summative field trials, which aim to assess what users can expect in terms of the classification's psychometric properties after the classification has been completed. A crucial component of an empirically guided diagnostic revision process is the use of developmental field trials in which data are collected from users regarding the feasibility, reliability, validity, and clinical utility of proposed changes that can assist in refining the proposals before they are finalised. The DSM-III and ICD-10 reliability field trials are best considered summative as they were done primarily to establish whether clinicians using operationalised definitions could achieve adequate diagnostic reliability. The DSM-III-R and DSM-IV field trials, which collected performance data targeting specific diagnostic categories, heralded the use of developmental field trial data as an important component in the construction of diagnostic criteria sets, a process being continued in the ICD-11 revision process. Although initially presented as developmental in nature, the DSM-5 field trials ended up being essentially summative. Although reliability estimates with highly sophisticated methodology were provided for 23 mental disorders, the absence of information regarding the reliability of specific diagnostic items and the reasons for diagnostic disagreement prevented this information from being used to address identified reliability issues. Developmental field trials enhance the empirical basis for stating that psychiatric classifications are evidence based and they ultimately contribute to the improvement of clinical care for patients.