Medico-legal assessment of disability in narcolepsy: an interobserver reliability study

Impairment because of narcolepsy strongly limits job performance, but there are no standard criteria to assess disability in people with narcolepsy and a scale of disease severity is still lacking. We explored: (1) the interobserver reliability among Italian Medical Commissions making disability and handicap benefit decisions for people with narcolepsy, searching for correlations between the recognized disability degree and patients' features; (2) the willingness to report patients to the driving licence authority and (3) possible sources of variance in judgement. Fifteen narcoleptic patients were examined by four Medical Commissions in simulated sessions. Raw agreement and interobserver reliability among Commissions were calculated for disability and handicap benefit decisions and for driving licence decisions. Levels of judgement differed on percentage of disability (P < 0.001), severity of handicap (P = 0.0007) and the need to inform the driving licence authority (P = 0.032). Interobserver reliability ranged from Kappa = -0.10 to 0.35 for disability benefit decision and from Kappa = -0.26 to 0.36 for handicap benefit decision. The raw agreement on driving licence decision ranged from 73% to 100% (Kappa not calculable). Spearman's correlation between percentages of disability and patients' features showed correlations with age, daytime naps, sleepiness, cataplexy and quality of life. This first interobserver reliability study on social benefit decisions for narcolepsy shows the difficulty of reaching an agreement in this field, mainly because of variance in interpretation of the assessment criteria. The minimum set of indicators of disease severity correlating with patients' self assessments encourages a disability classification of narcolepsy.