Decision rules for assessment of chronic solvent-induced encephalopathy: Results in 2370 patients

For the diagnosis of patients suspected of chronic solvent-induced encephalopathy (CSE), it would be helpful if the applied cognitive tests show a characteristic profile of impairment in this disease. We investigated the existence of such a profile. In 1997-2006 two expert teams in The Netherlands systematically examined 2370 patients referred for evaluation of suspected CSE. The procedure included two selection steps: (1) intake interview, using criteria of exposure, development of symptoms and absence of non-solvent causes, and (2) seven tests of the computerized Neurobehavioural Evaluation System (NES). Patients showing negligible impairments were considered free from CSE and were not further examined. The third step comprised a neuropsychological, neurological and exposure evaluation. Explicit decision rules for the diagnosis of CSE were developed, including a minimum score for cognitive impairment summarizing 25 cognitive tests. These rules were retroactively applied to 563 patients, comprising 513 patients who had regularly completed all diagnostic steps and a sample of 50 out of the approximately 450 patients with negligible impairments on the NES, who were fully examined. The data from this sample were extrapolated to the original number of 450. In the combined population of 963 patients, a calculated 301 patients were given the diagnosis 'Solely CSE', 242 'CSE and other disease', 158 'Other Disease' and 262 'No (known) disease'. In the Solely CSE patients, the most impaired tests regarded Verbal Fluency & -Similarities, Motor Speed and Simple Attention. A profile of test results that might support the identification of patients with CSE amongst the other referred patients, was not found. The diverging results of related cognitive tests indicate that the use of a core test battery is needed to improve comparability. We consider the decision rules as a step towards a more objective assessment of CSE.