Objective: The purpose of this study was to analyze the type and frequency of signs, symptoms, and ill-defined conditions (SSID; International Classification of Diseases-9th Revision, Clinical Modification (ICD-9-CM) codes 780-799) identified by physicians evaluating Persian Gulf War veterans; to determine the influence of the extent of evaluation on the type and frequency of SSID diagnoses; and to search for evidence for a new illness, or illness related to wartime exposures, in veterans with ill-defined conditions. Method: Comprehensive examinations were provided for 21,579 consecutive Persian Gulf War veterans with symptoms or health concerns after the war. Data recorded on all individuals includes demographics, self-reported exposures, symptoms, and physician-assigned ICD-9-CM primary and secondary diagnoses. A detailed psychosocial history, including a multidisciplinary discussion, was incorporated for a subset of participants. Results: SSID conditions were primary diagnoses for 17.2% of veterans, and either primary or secondary diagnoses for 41.8%. Although some SSIDs were objective conditions (eg, sleep apnea), most were simply symptoms. More comprehensive evaluation, especially the multidisciplinary discussion of findings, decreased the frequency of symptoms as diagnoses and increased the number of DSM-IV psychiatric diagnoses. Ill-defined conditions were not associated with particular self-reported exposures or demographic variables. Conclusions: Ill-defined conditions identified by physicians in Gulf War veterans are most often symptoms. More definitive, often psychological, diagnoses can be made by increasing the intensity of the evaluation and by multidisciplinary input. Evidence for a new or unique illness related to wartime exposures did not emerge from this analysis.
