Healthcare costs of invasive meningococcal disease: a nationwide population-based study using an innovative clustering method to identify sequelae.

BACKGROUND: Studies investigating the costs associated with invasive meningococcal disease (IMD) are scarce, primarily due to the disease rarity, its highly variable prognosis, and the potential for sequelae to develop long after the acute phase. We conducted a retrospective longitudinal cohort study to estimate the healthcare costs associated with IMD in France in the short (one month), medium (two years), and long (up to 12 years) term. METHODS: Using the National Health Data System (SNDS), we extracted data for all individuals hospitalised with a diagnosis of IMD (IMD+) between 1 January 2008 and 31 December 2018. Each IMD + individual was matched to up to four individuals without IMD. Among IMD + individuals discharged alive (exposed individuals), a K-modes clustering method using 64 healthcare resource utilisation (HCRU) variables to identify those with high HCRU levels (EIC+, for Exposed Individuals with Care), who served as a proxy for individuals with IMD sequelae. Additional costs associated with exposure were estimated using generalized estimating equations (GEEs). The cost analysis was conducted from the perspective of the National Health Insurance System. RESULTS: Of the 5,770 IMD + individuals (52.6% male; 29.7% aged < 5 years; 27.4% with comorbidities), 4,502 were exposed individuals (52.2% male; 30.9% aged < 5 years; 26.4% with comorbidities), of whom 1,032 were EIC+ (40.4% male; 7.9% aged < 5 years; 30.0% aged ≥ 65 years; 62.8% with comorbidities). The mean per capita costs of the index hospitalisation were €10,599 (SD: €16,931). These costs were €2,400 (SD: €10,565) in the short term (excluding the index hospitalisation), €9,304 (SD: €51,785) in the medium term, and €37,718 (SD: €114,143) in the long term. They were, respectively, 19.2 (aOR; 95%CI: 17.9-20.5), 1.3 (1.2-1.4), and 2.2 (2.0-2.5) times higher than those of the matched unexposed individuals. When the index hospitalisation was included, short-term costs were 86.3 (aOR; 95%CI: 81.2-91.7) times higher. CONCLUSIONS: The healthcare costs associated with IMD extend well beyond hospital discharge. The long-term management of sequelae significantly increases the economic burden of the disease, emphasising the importance of effective preventive strategies for IMD. The clustering method used in this study could facilitate the identification of IMD sequelae in real-world data. CLINICAL TRIAL NUMBER: Not applicable.