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

Background : Cost-of-illness studies for invasive meningococcal disease (IMD) are scarce, mainly because the disease is rare, its prognosis varies widely, and some sequelae can develop far from the acute phase. We conducted a retrospective longitudinal cohort study to estimate the healthcare costs associated with IMD in France, in the short (1 month), medium (2 years), and long (up to 12 years) term. Methods : Data up to 31 December 2018 were extracted from the National Health Data System (SNDS) database for all individuals hospitalised with a diagnosis of IMD between 1 January 2008 and 31 December 2018 (IMD+). Each individual was matched to up to four individuals without IMD. A K-modes clustering method using 64 healthcare resource utilization (HCRU) variables was used to identify, among IMD+ individuals discharged alive from hospital (Exposed individuals), those with a high level of HCRU (EIC+, for exposed individuals with care) who served as a proxy for individuals with IMD sequelae. The 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+ (male: 52.6%; <5 years: 29.7%; comorbidity: 27.4%), 4,502 were Exposed individuals (male: 52.2%; <5 years: 30.9%; comorbidity: 26.4%), of whom 1,032 were EIC+ (male: 40.4%; <5 years: 7.9%; ≥65 years: 31.6%; comorbidity: 39.3%). The mean per capita costs of the index hospitalisation were €10,599 (SD: €16,931). The mean per capita costs were €2,400 (SD: €10,565), €9,304 (SD: €51,785), and €37,718 (SD: €114,143) in the short term (excluding the index hospitalisation), the medium term, and the long term, respectively. These costs were 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, respectively. Short-term costs were 86.3 (aOR; 95%CI: 81.2-91.7) times higher when the costs of the index hospitalisation were included. Conclusions: The healthcare costs of IMD extend beyond hospital discharge. The management of long-term sequelae dramatically increases the cost of the disease, highlighting the need for effective preventive strategies for IMD. The clustering method could help identify sequelae after IMD in real-world data studies. Clinical trial number: not applicable